THALASSEMIA

Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion of a gene; results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin. This can cause the formation of abnormal hemoglobin molecules,thus causing anemia, the characteristic presenting symptom of the thalassemias. 

Types

Thalassemia is classified on the basis of which globin chain participating in hemoglobin formation is deleted. It is of two major types: Alpha Thalassemia and/or Beta Thalassemia:
 

Alpha Thalassemia is further classified on the number of gene deletions (4 in total):

  • Silent carrier(1 gene deletion)
  • Alpha trait(2 gene deletion)
  • HbH disease(3 gene deletion)
  • Alpha thalassemia major/Hydrops fetalis(4 gene deletion)

Beta Thalassemia is classified on basis of chain deletion (2 in total) rather than gene deletion as:

  • Beta thalassemia trait(1 chain deletion)
  • Beta thalassemia intermedia(2 chain deletion but mild variety)
  • Beta thalassemia major(2 chain deletion but severe variety)

SYMPTOMS (seen by parents)

Usually around 4-6 months of age

  • Increasing paleness
  • Poor feeding
  • Abdominal swelling

SIGNS (seen by physician)

  • The hallmark of thalassemia is anemia resulting from ineffective erythropoesis
  • Marked pallor
  • Signs of failure maybe present- tachycardia, tachypnea, hepatomegaly Splenomegaly

DIAGNOSIS

Complete blood counts show microcytic hypochromic (Low MCV/MCH) anemia, high white cell count, platelet count maybe raised.

 Peripheral smear shows hypochromic microcytic cells, anisocyosis, poikilocytosis, target cells.

 Hb electrophoresis is diagnostic. The patients as well as parents testing must be done. This test must be taken prior to blood transfusion. The patients study will show raised HbF and low HbA2 and HbA. The parents study will show raised HbA2 (>3.5%)

MANAGEMENT

The patient has to be managed with regular blood transfusion usually every 3-4 weeks with packed red cells which are leucodepleted. The pre transfusion Hb should not be allowed to fall <9gm/dl.

After around 10-12 transfusions chelation therapy must be started to rid the body of exxcess unusable iron. The iron status is monitored using serum ferritin. If not monitored iron deposition in liver, heart ,brain and other organs leads to failure of working of these organs and eventually death.

Iron is therefore removed using chelation therapy which can be oral/IV. Various drugs used are desferroxamine(IV), deferiprone and desferrasirox (oral). The oldest and yet best drug yet is desferroxamine.

Chelation is continued lifelong and the patient is monitoed of side effects of these drugs- white counts can drop, growth monitoring, hearing tests, liver and kidney functions.

However, the most important aspect of management still remains parent counselling. The parents are dealing with a chronic and incurable disease,hence counselling for further pregnancy is a must. This disease is autosomal recesive and follows mendelian laws of genetics. Hence, in each pregnancy there is a 25% chance of delivering a baby with thalassemia major.

At 16 weeks of pregnancy an amniocentesis is done to test for the genetic mutation causing thalassemaia. This mutation is previously identified in the parents. If the fetus has the mutations, abortion is advised else pregnancy is continued.

PREVENTION IS THE ONLY HOPE FOR THALASSEMIA!!!!!!!!!!!!!!!!!!

Thalassemia Package

Thalassemia Package: Rs. 2200/ per visit (Includes Pediatric Hematologist Consultation, Fully tested Crossmatched Leucoreduced Blood Transfusion, Complete Blood Count and Day Care File).

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MEGALOBLASTIC ANEMIAS

CLINICAL FEATURES

      Presenting symptoms

  • Asymptomatic
  • Symptoms of anemiar
  • Icterus
  • Developmental delay, hypotonia,

Neurologic

  • Cbl deficiency - patchy demyelination
  • Cerebral abnormalities
  • Subacute combined degeneration of the spinal cord
  • Parasthesias in the hands and feet
  • Early loss of vibration and position sensation
  • Progressive spastic and ataxic weakness.
  • Loss of reflexes due to a superimposed peripheral neuropathy
  • Optic atrophy and irritability and other mental changes
  • Signs diffuse rather than focal; generally symmetric
  • Predominant involvement of the posterior and lateral tracts, including Romberg's sign

Other Effects

  • Cbl deficiency more than folate deficiency - sterility 
  • Generalized melanin pigmentation that is reversible by specific nutrient replenishment.
  • Cbl deficiency
  • bactericidal activity and ­ susceptibility to TB.
  • In folate deficiency
    • lymphocyte subsets
    • predisposition to chemical-induced gastrointestinal carcinogenesis
  • Patchy demyelination begins in the dorsal columns in the thoracic segments of the spinal cord and then spreads contiguously to involve corticospinal tracts
  • Lesions spread throughout the length of the cord
  • Ultimately involve spinothalamic and spinocerebellar tracts
  • Degeneration of the dorsal root ganglia, celiac ganglia, and Meissners and Auerbachs plexus.
  • Demyelination may also extend to the white matter of the brain
  • Degeneration of the posterior spinal columns, which results in decreased vibration sense below the iliac crests in 48%, loss of position sense in the feet in 42%, and ataxia in 64% of patients.
  • Degeneration of the pyramidal tracts, which causes spasticity and dorsiflexion of the toes (Babinski reflex) in 56% of patients.
  • Peripheral neuropathy with distal paresthesia, anesthesia, and muscular weakness in 90% of patients.
  • Dementia mimicking Alzheimer's disease.
  • Depression, with or without dementia, in 90% of patients and affecting virtually all symptomatic patients.
  • Optic atrophy, which is very rare in pernicious anemia.

MATERNAL COBALAMIN DEFICIENCY

  • Cobalamin deficiency in newborns is most often the result of deficiency in the mother
  • Severely deficient mothers may be sterile
  • These mothers have low serum and milk cobalamin levels, and their infants are born with low cobalamin stores that are not repleted during breast-feeding
  • The mother has circulating anti–intrinsic factor antibodies, they may cross the placenta and impair intestinal cobalamin absorption during the initial weeks of life, particularly if the antibody titer is high

COBALAMIN DEFICIENCY IN NEWBORNS AND INFANTS

  • Demonstration of a low serum cobalamin level, an increased plasma total homocysteine level, and an increased plasma methylmalonic acid level, confirmed by response to parenteral cobalamin therapy.
  • Assessment of the mother's diet and cobalamin status is important because maternal cobalamin deficiency is the most common cause of cobalamin deficiency in newborns and infants.
  • In infants born to cobalamin-deficient mothers, severe cobalamin deficiency can develop in the early weeks of life. Indeed, cobalamin deficiency has become equated with severe megaloblastic anemia in children
  • Cobalamin deficiency has been reported after surgery for necrotizing enterocolitis, particularly when resection has included part of the terminal ileum
  • The consistency of reports documenting the permanence of neurologic damage induced by cobalamin deficiency in newborns, often despite therapy,
  • Treatment of cobalamin deficiency in newborns and infants needs to be aggressive to arrest and reverse the neurologic and psychomotor damage.
  • An initial cobalamin injection is recommended
  • A self-limited “infantile tremor syndrome” arising during cobalamin therapy 

COMMON CAUSES

  • B12 deficiency
  • FA deficiency
  • Others
    •  Congenital DNA synthesis defects
    • Acquired defects
    • Drug induced
  • Congenital DNA synthesis defects
  • Orotic aciduria
  • Thiamine responsive megaloblastic anemia
  • Congenital famililal reqiiring massive doses and FA
  • CDA
  • Lesch Nehan syndrome
  • Acquired defects
  • Liver disease
  • Sideroblastic anemias
  • Leukemias esp AML M6
  • Aplastic anemia
  • Refractory megaloblastic anemia
  • Drug induced
    • Purine analogues:  6MP, 6-TG, Azathioprine
    • Pyrimidine analogues:  5 FU, 5-Azauridine
    • Ribonucleotide reductase inhibitors: Cytarabine, Hydroxyurea

PATHOBIOLOGY

  • Common biochemical feature
  • Defect in DNA synthesis
  • Lesser alterations in RNA and protein synthesis
    •  State of unbalanced cell growth and impaired cell division

Normal

  • Majority of cells have DNA values of 2N = resting
  • Minority have DNA values of 4N  (N = amount of DNA in haploid genome). S phase

Megaloblastic anemia

  • Majority of megaloblastic cells are not resting but vainly engaged in attempting to double their DNA, with frequent arrest in the S phase and lesser arrest in other phases of the cell cycle.
  • An ­ % of cells have DNA values between 2N and 4N because of delayed cell division.
  • DNA in megaloblastic cells is morphologically expressed as larger than normal immature nuclei with finely particulate chromatin
  • Relatively unimpaired RNA and protein synthesis results in large cells with greater mature cytoplasm and cell volume. 
  • The net result – cell with arrested nuclear maturation but normal cytoplasmic maturation independent of the nuclear events.
  • Morphologically - megaloblastic
  • Each cell lineage has unique repertoire of expression of defective DNA synthesis.
  • Influenced by the normal patterns of maturation of the affected cell line.
  • Additional variables that affect RNA and protein synthesis can lead to modification of megaloblastic expression.

CHANGES IN B12/FA DEFICIENCY

  • All proliferating cells exhibit megaloblastosis 
  • Striking changes in Blood and BM
  • Epithelial cells
    • gastrointestinal tract (buccal mucosa, tongue, small intestine)
    • cervix, vagina, and uterus

MORPHOLOGY IN MEGALOBLASTOSIS FROM COLBALAMIN AND FOLATE DEFICIENCY IS THE SAME

CBC/Peripheral Smear

  • Mean corpuscular volume (MCV) with macroovalocytes with varying anisocytosis and poikilocytosis

  • Nuclear hypersegmentation of neutrophils -1 PMN with 6 lobes or 5% with 5 lobes

  • Thrombocytopenia

  • Leukoerythroblastic morphology (from extramedullary hematopoiesis) 

Bone Marrow

  • Bone marrow aspirate is better than biopsy 

Bone Marrow Aspirate 

  • General increase in cellularity of all three major hematopoietic elements
  • Abnormal erythropoiesis
    •  orthochromatic megaloblasts 
  • Abnormal leukopoiesis
    • giant metamyelocytes and band forms (pathognomonic)
    • hypersegmented neutrophils
  • Abnormal megakaryocytopoiesis
    •  pseudohyperdiploidy
  • What appears as exuberant cell proliferation with numerous mitotic figures, the cells are actually very slowly proliferating.
  • Erythroid hyperplasia reduces the myeloid/erythroid ratio from 3:1 to 1:1

TREATMENT

  • Initial dose of 10 μg CNCbl may be given subcutaneously for 2 days. This therapy is sufficient to normalize serum lactate dehydrogenase and iron levels and induce reticulocytosis in 5 to 7 days, but insufficient to normalize plasma methylmalonic acid and total homocysteine levels and replete body stores. 
  • For severely affected children, the dose of CNCbl is 0.2 μg/kg/day subcutaneously for 2 days.
  • Complete correction of megaloblastosis and associated metabolic changes requires anywhere from 15 to 150 μg of CNCbl.
  • Conventional therapy has been 1000 μg of CNCbl or OHCbl by injection daily for 1 week, followed by 100 μg of CNCbl weekly for 1 month and then monthly thereafter.
  • Oral therapy with 1 to 2 mg cobalamin daily is cheaper and better tolerated and has become standard treatment in many countries
  • Whether oral therapy arrests the neurologic toxicity as quickly as parenteral dosing does is not yet known

DEFECTS

CAUSES OF B12 DEFICIENCY

  • Inadequate intake
    • Vegans, poorly controlled PKU diet, malnutrition
    • Maternal B12 Deficiency
  • Defective Absorbtion
    •  Failure of IF
    • Failure in absorption small intestine
    • Defective Transport
    • Metabolic Defects
  • Failure of IF
    • Congenital absence – normal mucosa
    • Qualitative
    • Quantitative
    • Juvenile PA
    • Juvenile PA with polyendocrinopathies
    • Juvenile PA with IgA deficiency
    • Gastric mucosal disease – corrosives, Gastrectomy
  • Failure in absorption small intestine
    •  Specific
    • Abnormal IF
    • Defective IF transport by enterocytes – Imerslund Gräseback syndrome
    • Chelating agents. – Bind Ca++
  • Generalised malabsorbtion
    •  Intestinal Resection
    • Crohns disease
    • TB
    • Malignancy– lymphosarcoma
    • Pancreatic insufficiency
    • Zollinger Ellison Syndrome
    • Celiac Disease, Tropical Sprue
    • Non Specific Malabsorbtion Syndromes
    • HIV
    • antacids
    • Neonatal NEC
  • Competition
    • Small bowel overgrowth – anastomoses Fistulae, blind loop
    • D. latum, Giardia, Strongyloides stercoralis
  • Defective Transport
    • Congenital TC II defect
    • Transient TC II deficiency
    • Partial R-binder defect
  • Defects in B12 metabolism
    •  CONGENITAL 
  • Adenosyl cobalamine deficiency CblA & CblB diseases
  • Methylcobalamine deficiency Cbl E &Cbl G
  • Combied Methyl and adenosyl Cll Deficienct – Cbl C, Cbl D, Cbl F
  • Methyl malonyl CoA mutase defect
    •   ACQUIRED
  • Liver disease
  • PEM
  • Drugs – impaired absorbtion/utilization: PAS, colchicine, Neomycin, ethanol, OC pills, Metormin

FOLIC ACID

DEFECTS

       Causes of FA deficiency

  • Inadequate intake
    • Poor diet
    • Poor cooking practices
    • Defective absorption
    • Goat’s milk
    • Heat sterilized food in post BMT
    • PKU, MSUD
    • Prematurity
  • Defective Absorption
  • Congenital isolated folate malabsorbtion
    • Accuired 
  • Idiopathic steatorrhea
  • Tropical sprue
  • Total/Partial gastrectomy
  • Diverticula of small intestine
  • Jejunal resection
  • Regional ileitis
  • Whipples disease
  • Lymphoma of intestine
  • Post BMT
    •  Drugs
  • Phenytoin
  • Primidone
  • Barbiturates
  • OC pills
  • Cycloserine
  • Metformin
  • Alcohol
  • Dietary: glyceine, methionine 
  • Increased Requirements
    •  Rapid growth ex prematurity
    • Chronic hemolytic anemia
    • Dyserythropoietic anemias
    • Malignancy – leukemia , lymphoma
    • Hypermetabolic states – infection, Hyperthyroidism
    • Cirrhosis
    • Post BMT
    • Folate metabolism defects
    • Congenital deficiencies of
  • MFHTR
  • Glutamate formiminotransferase
  • Functional/primary  N5Methyl THF homocysteine transferase
  • Dihydrofolate reductase
  • Methyl-THF cyclohydrolase
    •  Aquired
  • FA antagonists – MTX, TMP, pyrimethamine, pentamidine
  • Cbl deficiency
  • Alcoholosm
  • Liver disease
  • Increased Excretion
    •  Cbl def
    •  Dialysis
    • Liver and heart disease
  • APPROACH TO DIAGNOSIS

      Normal Values

 

  Mean Corpuscular Volume (fl)  
  Mean -2SD 
Birth(cord_blood) 108 98
1_to_dayscapillary) 108 95
 1 wk 107  88
2 wk 105 86
1 mo  104 85
2mo 96 77
3 to 6 mo 91 74
0.5 to 2.0 yr 78 70
2 to 6 yr 81 75
6 to 12 yr 86 77
12 to 18 yr    
Female 90 78
Male 88 78
18 to 49 yr    
Female 90 80
Male 90 80

  • PERIPHERAL SMEAR
  • BONE MARROW ASPIRATE
DIAGNOSIS OF B12-FA DEFICIENCY – BIOCHEMISTRY
  • Early manifestations of negative Cbl balance are
    •  abnormal deoxyuridine suppression test
    • increased serum methylmalonic acid (MMA)
    • tHcys levels
  • This occurs at a time when the total Cbl in serum is still normal.
  • Continued negative Cbl balance leads to an absolute decrease in serum Cbl level.
  • THcys - metabolic evidence for folate deficiency increased is often found when serum folates are still in the low-normal range.

SUBCLINICAL OR PRECLINICAL PERNICIOUS ANEMIA

  • Erythrocyte macrocytosis, detected by electronic blood cell analysis, identifies patients with pernicious anemia and others with cobalamin deficiency. 
  • Still others are identified through screening programs in at-risk populations, such as the institutionalized, the elderly, and those with neurologic or psychiatric impairments.
  • The diagnosis is usually established by finding a low serum cobalamin or plasma holo-TC level together with an elevated plasma methylmalonic acid or total homocysteine level.

CHRONOLOGICAL ORDER OF ABNORMAL TESTS

  • Metabolite tests reflective of decreased intracellular nutrient availability
  • Followed by biochemical evidence of abnormal thymidylate synthesis (impaired conversion of dUMP to dTMP)
  • Morphologic expression of perturbed DNA in PMNs (lobe index), macroovalocytosis, and anemia.

Total Serum Homocysteine (tHcys) and Methylmalonic Acid (MMA) Level

  • Reduced activity of the Cbl-dependent enzyme
  • Activity of methionine synthase - ­ serum tHcys,
  • Activity methylmalonyl-CoA mutase - to convert methylmalonyl-CoA to succinyl-CoA -­ MMA levels
  • Serum tHcys + MMA can distinguish between Cbl and folate deficiency
  • Folate deficiency - normal MMA levels or mild elevations
  • Positive response to Cbl, documented by falling levels of tHcys and MMA - of Cbl deficiency
  • Rx folate - ¯ in the isolated tHcys level

FALSELY LOW SERUM CBL IN THE ABSENCE OF TRUE CBL DEFICIENCY

  • Folate deficiency (1/3 of patients)
  • Multiple myeloma
  • TC I deficiency
  • Megadose vitamin C therapy
  • Patients serum contains other radioisotopes (99m Tc or 67 Ga and other radiopharmaceuticals used in organ scanning)

FALSELY RAISED CBL LEVELS IN THE PRESENCE OF A TRUE DEFICIENCY

  • Cbl binders (TC I and II) increased (myeloproliferative states, hepatomas, and fibrolamellar hepatic tumors)
  • TC II-producing macrophages are activated (autoimmune diseases, monoblastic leukemias, and lymphomas)
  • Release of Cbl from hepatocytes (active liver disease)

ALTERNATIVE TESTS

  • % saturation of TC II – Technical issues and validation failure
  • Urinary MMA test - inadequate clinical data, Renal dysfunction and dehydration factors, on the kinetics of reduction of urinary MMA to Cbl replacement
  • Deoxyuridine suppression test : not widely available
  • B12 absorption-levels after oral b12
  • Urinary excretion using cobalt 58-accurate urine measurement, b12/folic acid deficiency leads to decreased renal absorption 
  • B12 binding capacity-plasma transcobalamine measurement
  • Holo TC- first to diminish

Schillings test

TREATMENT

Folate Deficiency

  • Orally or parenterally in a dose of 0.5–1mg/day several months
  • No specific diagnosis -, smaller doses of folate (0.1mg/day) X week ( diagnostic test, - hematologic response in 72hr.)
  • Dihydrofolate reductase deficiency : N5 formylTHF

Response

  • Hematological
    • Hemoglobin: 2-6 weeks
    • Reticulocytosis
  • Begins : 2-4 days
  • Peaks 4-7 days
  • Marrow
    • Diminish 24-48 hrs
    • Giant meta and Band: longer
  • Ser Iron  falls 24-48 hrs
  • Sense of wellbeing and appetite : 1-2 days

B12 DEFICIENCY

  • 1000 mcg x 7 days
  • 100m mcg/week x 4 doses
  • 1000 mcg 1-3 monthly
  • Wth K supplimentation
  • Mega Doses in
    • Methylmalonic acidemia
    • TCII deficiency

Response

  • Hematological
    •  Reticulocytosis
  • Begins : D3-4
  • Peaks : D 6-8
  • Normalises: D 20
    •  Marrow
  • Begins: 6 hrs
  • Completes: 72 hrs
  • Neurological
    • Alertness and responsiveness: 48 hrs
    • Delayed milestones: several months
  • An unexplained sense of energy described by some patients in the first 24 hours.
  • Peak reticulocyte count 1 week after starting treatment. 
  • Obtain iron studies because coexisting iron deficiency
  • Corpuscular volume (MCV), should be completely normal by the eighth week.
  • A failure of homocysteine or MMA to normalize during the first week suggests an incorrect
  • Neurologic improvement begins within the first week also and is typically complete in 6 weeks to 3 months.
  • Progression always calls for diagnostic ressessment.
  • Residual disability, estimated to affect 6% of neurologic patients,4 is the most feared outcome of cobalamin deficiency and is likely to persist if still present after 6 to 12 months of treatment.
  • Irreversibility is associated with more than 6 months of therapeutic delay,
  • Associations of adverse neurologic outcomes with folate therapy

  • As long as malabsorption persists, deficiency progresses, and clinical consequences may appear within “only” 2 to 5 years.
  • IF antibody sensitivity is poor (50%-70%), making the Schilling test necessary when antibody is absent.
  • Serum gastrin and pepsinogen I abnormalities can sometimes help because of their high sensitivities for PA (90%-92%), but they lack specificity.
  • Whether given parenterally or orally, 1000-g doses are needed to accommodate wide variations in diffusion and retention among patients.
  • 8 to 10 injections over the first 2 to 3 months before considering monthly injections.
  • This augments repletion and helps delay relapse should the patient discontinue treatment,
  • Hydroxocobalamin injections can be spaced at twice the interval for cyanocobalamin.
  • Individual variations, 1000 g must be taken daily if malabsorption

Parenteral vs oral maintenance in patients with malabsorption

  • Advantages in ease, cost, and comfort,
  • Possible disadvantages of dosing with meals.
  • Relapse in patients with IF-related malabsorption occurs within 1 to 2 years. 
  • MMAor homocysteine is a better monitoring tool than serum cobalamin and provides early warning of relapse if measured annually.

RECOMMENDED DAILY ALLOWANCE

DIETARY SOURCES

Sources of Cbl (VIT B12) 

  • Cbl is only produced in nature by Cbl-producing microorganisms.
  • Humans -  solely from diet.
  • Herbivores - from plants contaminated with Cbl-producing bacteria that grow in roots and nodules of legumes.
  • Exogenous contamination of plants by feces
  • Carnivores - Cbl supply by ingesting tissues.
  • Cbl is produced by bacteria in the large bowel of humans - too distal for absoption
  • Food Cbl is stable to high-temperature cooking processes
  • Converted to inactive analogues by ascorbic acid.
  • Animal protein is the major dietary Cbl source.
  • Meats from parenchymal organs are richest in Cbl > fish and animal muscle, milk products egg yolk
  • Of the total body content of 25 mg in adults, 1 mg is in the liver.
  • There is an obligatory loss of 0.1% per day regardless of total body Cbl content.
  • It takes 34 years to deplete stores if abruptly stopped
  • Longer in V/O enterohepatic circulation

Sources of Folic Acid

  • Leafy vegetables (spinach, lettuce, broccoli, beans)
  • Fruits (bananas, melons, lemons)
  • Yeast, mushrooms,
  • Animal protein (liver, kidney)
  • Human breast milk
  • Pasteurized cow's milk.
  • Infant formulas
  • Goat's milk / powdered milk is deficient
  • Increased vitamin requirements - pregnancy, growth in infancy, chronic hemolysis.
  • The normal infant daily requirement is 25–35 µg/day.
  • The requirements on a weight basis are higher in children than adults, - increased needs of growth
  • Extremely thermolabile 
  • Prolonged cooking (for >15 minutes)
  • In large quantities of water 
  • Absence of reducing agents
  • Oxidation of food folate by nitrites reduces its bioavailability.
  • Pteroylpolyglutamates - absorbed less efficiently than pteroylmonoglutamate 
  • Foods (cabbage, lettuce, orange) are not well absorbed
  • Other dietary folates are nutritionally available
  • Enterohepatic circulation

RARE CAUSES – INBORN ERRORS

Deficiency of Intrinsic Factor

  • Appears after the first year but before the fifth year of life
  • Ormal gastric acid secretion and normal findings on gastric cytologic examination
  • No detectable intrinsic factor is produced
  • Immunologically reactive but nonfunctional intrinsic factor
  • Reduced affinity for cubam, reduced affinity for cobalamin 

Imerslund-Gräsbeck Syndrom

  • Failure to thrive, recurrent gastrointestinal or respiratory infections, pallor, and fatigue.
  • Megaloblastic anemia is usually present. Neurologic signs may be relatively mild
  • Proteinuria that is neither of the classic glomerular or tubular type
  • Deficiency of the intrinsic factor–cobalamin receptor complex, cubam.
  • The proteinuria is a result of disruption of cubam function in the proximal tubule of the kidney
  • Treatment involves intramuscular injection of cobalamin, initially at 1 mg OHCbl daily for 10 days, followed by monthly injection afterward.

Transcobalamin Deficiency

  • At a much earlier age than in patients with other causes of cobalamin malabsorption, usually in the first months of life
  • Severe immunologic deficiency with defective cellular and humoral immunity
  • Mutations in the TCN2
  • Serum cobalamin levels must be kept very high if transcobalamin-deficient patients are to be treated successfully. Levels ranging from 1000 to 10,000 pg/mL have been required and are achieved with doses of oral OHCbl or CNCbl twice weekly (500 to 1000 μg) or with systemic administration of CNCbl or OHCbl (1000 μg) weekly or more often.

Haptocorrin (R Binder, Transcobalamin I or III) Deficiency

  • Deficiency or complete absence of haptocorrin in plasma, saliva, and leukocytes
  • Although serum cobalamin levels are low, holo-TC levels are normal and the patients are not clinically deficient in cobalamin
  • Optic atrophy, ataxia, long tract signs, and dementia
  • Haptocorrin may play a role in the scavenging of cobalamin analogues that may be toxic to the brain

Inborn Errors of Cobalamin Metabolism

  • Homocystinuria, methylmalonic aciduria, or both, depending on whether synthesis of MeCbl, AdoCbl, or both cobalamin cofactors
  • Only disorders in which synthesis of MeCbl is impaired, either alone (cblE, cblG, cblD variant 1) or in combination with AdoCbl synthesis (cblC, cblD, cblF), are characterized by megaloblastic anemia.
  • The diagnosis of inborn errors of cobalamin metabolism is usually carried out with the use of cultured fibroblasts
  • Molecular diagnosis
  • Prenatal diagnosis by biochemical analysis of cultured amniocytes or chorionic villus cells has been sought for most of the classes of inborn errors of cobalamin metabolism
  • Analysis of amniocytes appears to be more reliable than that of chorionic villus cells. In addition, gas chromatography–mass spectroscopy or liquid chromatography–tandem mass spectroscopy has been used to detect the presence of methylmalonic acid or homocysteine in amniotic fluid.

Functional Methionine Synthase Deficiency

  • Functional methionine synthase deficiency is characterized by elevated plasma homocysteine, homocystinuria, and hypomethioninemia without methylmalonic aciduria.
  • Two distinct groups of patients have been identified: cblE and cblG.
  • The clinical and biochemical findings in the two disorders are virtually identical.
  • Patients are usually seen initially in the first 2 years of life, but some have not been symptomatic until adulthood. The most common findings in both cblE and cblG disease include megaloblastic anemia and various neurologic problems, including developmental delay and cerebral atrophy.
  • Other findings include electroencephalographic abnormalities, nystagmus, hypotonia, hypertonia, seizures, blindness, and ataxia. Findings in patients with adult onset of symptoms have typically involved neurologic or psychiatric symptoms. 
  • Fibroblasts from both cblE and cblG patients show decreased synthesis of MeCbl and decreased activity of methionine synthase in the presence of normal AdoCbl synthesis and methylmalonyl-CoA mutase activity]

Combined Deficiency of Adenosylcobalamin and Methylcobalamin

The cblC Disorder

  •  Homocystinuria and methylmalonic aciduria; in addition, hypomethioninemia and cystathioninuria are present.
  • The infant is usually seen in the first year of life because of lethargy, poor feeding, failure to thrive, and developmental delay.
  • Most patients have megaloblastic anemia, and some have hypersegmented neutrophils and thrombocytopenia.
  • Later in childhood or in adulthood, with findings of spasticity, myelopathy, delirium, dementia, or psychosis.
  • A characteristic pigmentary retinopathy with perimacular deg
  • Features of hemolytic-uremic syndrome.
  • Other reported findings in cblC disease include erosive dermatitis, hydrocephalus, and hepatic failure.
  • Fibroblasts from cblC patients show decreased synthesis of both MeCbl and AdoCbl and decreased function of both methionine synthase and methylmalonyl-CoA mutase
  • CblC disorder, MMACHC on chromosome 1p34.1
  • Therapy for cblC disease can be difficult, particularly in patients with early onset. About a third of patients with onset in the first month of life die.
  • Some patients have improved with OHCbl therapy, 1 mg/day by injection, as assessed by a reduction in methylmalonic acid and homocystine excretion.
  • Studies suggest that OHCbl rather than CNCbl should be used.
  • Systemic OHCbl treatment was much more effective than oral therapy, and betaine (250 mg/kg/day) appeared to be helpful when used in combination with OHCbl.
  • Neither folinic acid nor carnitine had any effect
  • Therapy with daily oral betaine and biweekly injections of OHCbl resulted in a reduction in methylmalonic acid levels, normalization of serum methionine and homocysteine concentrations, and resolution of lethargy, irritability, and failure to thrive. However, complete reversal of the neurologic and retinal findings did not occur, which emphasizes the need for early diagnosis and treatment. 

FOLATE METABOLIC DEFECTS

Hereditary Folate Malabsorption

  • Megaloblastic anemia and low serum folate levels appear in the first few months of life, with excretion of FIGlu and orotic acid in urine.
  • Patients with hereditary folate malabsorption fail to absorb folic acid or reduced folates across the intestinal membrane and the choroid plexus, thereby resulting in decreased folate levels in both blood and CSF
  • Autosomal recessive disorder
  • Hematologic changes respond to relatively low levels of folate, but levels in CSF may remain low
  • Oral and parenteral administration of folate in pharmacologic doses has corrected the hematologic abnormalities in some patients, with less effect in correcting the low folate levels in CSF.
  • Folinic acid and methyltetrahydrofolic acid may be more effective in entering CSF
  • Oral doses of folates in excess of 100 mg daily or systemic therapy may be needed. Intrathecal folate may be needed if CSF levels remain low.

Aplastic Anemia in Children

 Aplastic anemia is rare disease. The incidence is 1-2 new cases/million/ year. It occurs in all age groups but is found more commonly among the young. The incidence is higher in south-east Asia and  in poor countries; this may be due to viral infections and exposure to toxins.

Aplastic anemia (AA) is a heterogeneous disease, a form of bone marrow failure that presents with pancytopenia of abrupt or insidious (slow) onset and an empty bone marrow. There are marrow and peripheral blood criteria (bone marrow cellularity <30%; reticulocytes <20x109/L, platelets <20x109/L, and neutrophils <0.5x109/L) to define the severity of the condition.Primarily the management requires the establishment of diagnosis and the distinction between inherited Bone Marrow Failure (BMF) syndromes and acquired AA. Every child must undergo workup for the same as phenotypic features of BMF syndromes may not be evident in 25-40% children.

Another management issue is the analysis of Paroxysmal Nocturnal Hemeturia (PNH) clone in these children.  PNH is a rare diagnosis in pediatrics and the clinical significance of a small PNH clone in aplastic anaemia as detected by flow cytometry remains uncertain. Such clones can remain stable, diminish in size, disappear or increase. What is clinically important is the presence of a significant PNH clone with clinical or laboratory evidence of haemolysis.

TREATMENT

Patients with acquired AA can be offered three different treatment strategies, based on the level of cytopenia.

Alpha Thalassemia is further classified on the number of gene deletions (4 in total):

  • Patients with moderate cytopenia, not requiring transfusions, can be offered supportive care or outpatient treatment with anabolic steroids and/or low-dose steroids or cyclosporine (CsA). Androgens have been shown to increase telomerase activity in human CD34+ cells, which may provide an explanation for their effect, in some patients with AA.
  • Patients with cytopenia requiring transfusions should be treated as inpatients, with either Immunosupressive therapy (IST) or bone marrow transplantation (BMT), and the decision to begin treatment should not be delayed, as this may significantly decrease the chance of success.
  • The choice between these two treatments is based on severity of the disease and patient age: young patients (<20 years) with VERY SEVERE APLASTIC ANEMIA are candidates for first-line transplantation. Older patients with a higher PMN count are generally offered IST as initial therapy.

Supportive Care

The mainstay of AA therapy is supportive care with blood component therapy. Red cell and platelet transfusions should be given to maintain a safe haemoglobin level and platelet count and not be withheld for fear of sensitizing the patient. Pre-storage leucocyte depletion of all units of red cells and platelets must be done. Prophylactic platelet transfusions should be given when the platelet count is < 10 x 109/l (or < 20 x 109/l in the presence of fever) 

 It is unclear whether red cell and platelet transfusions should be routinely irradiated in all aplastic anaemia patients. Empirical use of irradiated blood components is for patients receiving immunosuppressive therapy and is to be continued until the lymphocyte count recovers to > 1.0 x 109/l .Absolute requirement for irradiated red cell and platelet transfusions is from the beginning of the pre-transplant conditioning regimen and applies to all patients undergoing stem cell transplantation.

Factor Support 

The use of G-CSF has been described in conjunction with ATG and CsA as first-line treatment.The potential advantages of using G-CSF are faster neutrophil recovery and the opportunity to test for white blood cell (WBC) increments and therefore predict failures and may allow early referral for BMT. A correlation was also found between duration of exposure to G-CSF and clonal disease.

Immunosuppressive Treatment

Treatment with antithymocyte globulin (ATG) yields superior survival when compared with supportive care. Combinations of ATG with androgens or CsA improve the overall response rates, but not survival.  The median time to achieve a response is 120 days, so a second treatment should not be planned earlier than 4 months after the initial ATG treatment. Responses can be subdivided in complete and partial: the former would require patients with a Hb >10 G/dL, a PMN >2x109/L and platelets > 100x109/L. Partial responses require at least transfusion independence.  

Both horse ATG and rabbit ATG have been used successfully. ATG may cause allergic reactions, but with appropriate premedication with steroids/antihistamines and appropriately slow infusion (up to 24 hours for each dose), nearly all patients can complete the prescribed total course of ATG, usually lasting 5 days.

Patients not responding to two courses of ATG will not respond to a third course and this should be avoided. The overall risk of developing a clonal cytogenetic abnormality/MDS at 10 years is set between 5% and 20% and may depend on the degree of response to IST.

Cyclosporin should be started on the 10th day of ATG therapy and continued for atleast a year. Monitoring of trough cyclosprin levels should be done along with renal function and BP monitoring. Tapering should be very slow (less than 10% of the dose/month) for at least 1 year, to minimize the risk of relapse.The response of ATG+ CsA is reported in western literature as 70-80%  but the response in our experience is about 10-20%

HLA Identical BMT

For children with idiopathic AA and a human leucocyte antigen (HLA)-matched sibling donor (MSD), allogeneic haematopoietic stem-cell transplantation (AHSCT) is the primary therapy of choice, although graft-versus-host disease remains a cause of long-term morbidity. It is recommended that bone marrow stem cells, and not G-CSF mobilised peripheral blood stem cells (PBSC) should be used. It is important to give at least 3 x 108 nucleated marrow cells/kg because at lower doses the risk of graft rejection increases significantly. Compared with bone marrow transplants, umbilical cord blood (UCB) transplants are associated with a lower risk of acute and chronic GVHD. UCB transplantation may also be considered in children who lack an HLA identical sibling donor or a fully matched unrelated adult donor.

 The conditioning regime used is a non-myeloablative and highly immunosuppressive regimen to help prevent graft rejection, and GVHD. The current standard regimen used is high dose cyclophosphamide and ATG 

The recommended post transplant immunosuppression is cyclosporine continuing for 12 months with tapering beginning at 9 months to help prevent late graft failure, and short course methotrexate 

The current survival for patients with AA younger than 16 years who have received a BMT from an HLA-identical sibling after conditioning with 200 mg/kg CY is 91%.
There is a significant risk of late graft failure in aplastic anaemia following allogeneic BMT which is most commonly associated with discontinuing cyclosporin too early or low cyclosporin blood levels.

Matched Unrelated Doner BMT may be considered when a patient has a fully matched donor, they are < 50 years old (or 50-60 years old with good performance status), and have failed at least one course of ATG and cyclosporin, have severe aplastic anaemia.

The optimal conditioning regimen for MUD BMT is uncertain, but currently a Fludarabine, non-irradiation-based regimen is favoured for younger patients. The EBMT reports overall survival of between 65% and 73% at 5 years

 Prednisolone should not be used to treat patients with aplastic anaemia because it is ineffective and encourages bacterial and fungal infection. and can precipitate serious gastrointestinal haemorrhage in the presence of severe thrombocytopenia

GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY

INTRODUCTION

Glucose-6-Phosphate Dehydrogenase Deficiency commonly known as G-6-PD deficiency is common in the malaria belts. It manifests as a hemolytic anemia in children when anti malarial drugs are given. The child is usually diagnosed when investigation of hemolytic anemia is done occurring in some individuals treated for malaria with 6-methoxy-8-aminoquinoline drugs.

HISTORY

Biochemical pathways through which red cells metabolize sugar were painstakingly unraveled by Warburg, Embden, and Meyerhof and were the result of tests performed on prisoner volunteers serving sentences in various prisons.

THE MECHANISM OF HEMOLYSIS

The hemolytic process is the inability of the erythrocytes to protect sulfhydryl groups against oxidative damage. There is targeted disruption of the gene encoding leading to hemolysis (breakdown of Red Blood Cells). On microscopic examination there is appearance of Heinz bodies both in vivo and in vitro in G6PD-deficient cells and their inability to protect their GSH against drug challenge. Glutathione peroxidase has little effect on oxidation of hemoglobin of murine cells challenged with peroxides. 

DRUGS AND CHEMICALS TO BE AVOIDED BY PERSONS WITH G6PD DEFICIENCY

  • Acetanilid
  • Diaminodiphenyl sulfone
  • Furazolidone (Furoxone)
  • Glibenclamide
  • Henna (Lawsone)
  • Isobutyl nitrite
  • Methylene Blue
  • Naphthalene
  • Niridazole (Ambilhar)
  • Nitrofurantoin (Furadantin)
  • Phenazopyridine (Pyridium)
  • Phenylhydrazine
  • Primaquine
  • Sulfacetamide
  • Sulfanilamide
  • Sulfapyridine
  • Thiazolesulfone
  • Trinitrotoluene
  • Urate oxidase

DRUGS THAT PROBABLY CAN BE SAFELY GIVEN IN NORMAL THERAPEUTIC DOSES TO G6PD-DEFICIENT PATIENTS WITHOUT NONSPHEROCYTIC HEMOLYTIC ANEMIA 

  • Acetaminophen
  • Acetophenetidin (phenacetin)
  • Acetylsalicylic acid (aspirin)
  • Aminopyrine (Pyramidon, aminopyrine)
  • Antazoline (Antistine)
  • Antipyrine
  • Ascorbic acid (vitamin C)
  • Benzhexol (Artane)
  • Chloramphenicol
  • Chlorguanidine (Proguanil, Paludrine)
  • Chloroquine
  • Colchicine
  • Diphenyldramine (Benadryl)
  • Isoniazid
  • L-Dopa
  • Menadione sodium bisulfite (Hykinone)
  • p-Aminobenzoic acid
  • p-Aminosalicylic acid
  • Phenylbutazone
  • Phenytoin
  • Probenecid (Benemid)
  • Procainamide hydrochloride (Pronestyl)
  • Pyrimethamine (Daraprim)
  • Quinine
  • Streptomycin
  • Sulfacytine
  • Sulfadiazine
  • Sulfaguanidine
  • Sulfamerazine
  • Sulfamethoxazole (Gantanol)
  • Sulfamethoxypyridazine
  • Sulfisoxazole (Gantrisin)
  • Tiaprofenic acid
  • Trimethoprim
  • Tripelennamine (Pyribenzamine)
  • Vitamin K

OTHER CAUSES OF HEMOLYSIS IN G-6-PD DEFICIENCY:

  • INFECTION-INDUCED HEMOLYSIS- Infection is was the most common precipitating factor of hemolytic anemia among G6PD-deficient patients.
  • FAVISM -All patients with favism are G6PD deficient, but many G6PD-deficient individuals can eat fava beans with impunity. Thus, the deficiency is a necessary but not sufficient cause of hemolysis. Glycosides divicine and isouramil
  • HEREDITARY NONSPHEROCYTIC HEMOLYTIC ANEMIA-Chlidren with hereditary nonspherocytic hemolytic anemia had a subset of G6PD variants that were functionally much more severe than the polymorphic mutations. 
  • NEONATAL JAUNDICE -may lead to kernicterus.

DIAGNOSIS

  • The Heinz body test
  • The glutathione stability test
    •  These tests are indirect.
  • Reduction of NADPH, invisible to the naked eye, was linked to the reduction of the visible dye brilliant cresyl blue.
    •  Tests using as visual endpoints the reduction of substances such as methylene blue, MTT tetrasodium, dichloroindophenol, or methemoglobin,
  • Fluorescent spot test
  • Correct diagnosis of patients who have recently undergone hemolysis may be obscured by the large proportion of young cells in the circulation. Harvesting the most dense cells after centrifugation may allow a more accurate diagnosis and waiting for a week or 2 is usually sufficient to establish the correct diagnosis.
  • Mild variants , females  with carrier is difficult
  • There is no biochemical method that is entirely reliable in the detection of heterozygotes. Only DNA analysis serves this purpose.

ALL G6PD DEFICIENCY IS NOT THE SAME

  • There appeared to be 2 types of mutations among Africans:
    • G6PDA, a normally active enzyme with rapid electrophoretic mobility,
    • G6PDA, an enzyme with the same mobility as G6PDA,
  • The enzyme among Mediterranean subjects
    •  Designated as G6PD B /G6PD Mediterranean.  
  • More than 370 variants had been described.

CHALLENGES

  • The development of simple means of testing new drugs in vitro to determine whether they will cause hemolysis in patients 

TREATMENT 

  • Stop the offending drug
  • Symptomatic treatment of hemoysis
  • Adequate hydration of the child.
  • Visit your pediatric hematologist immediately.