CLASSIFICATION MEGALOBLASTIC ANEMIA COBALAMIN DEFICIENCY :
1. INADEQUATE DIET - VEGETARIANS ( RARE)
2. MALABSORPTION
A.DEFECTIVE RELEASE OF COBALAMIN FROM FOOD
* GASTRIC ACHLORHYDRIA
* PARTIAL GASTRECTOMY
* DRUGS THAT BLOCK ACID SECRETION
B. INADEQUATE PRODUCTION OF INTRINSIC FACTOR ( IF )
* PERNICIOUS ANEMIA
* TOTAL GASTRECTOMY
* CONGENITAL ABSENCE OR FUNCTIONAL ABNORMALITY OF IF ( RARE )
C. DISORDERS OF TERMINAL ILEUM
* TROPICAL SPRUE
* NONTROPICAL SPRUE
* REGIONAL ENTERITIS
* INTESTINAL RESECTION
* NEOPLASMS & GRANULOMATOUS DISORDERS ( RARE )
* SELECTIVE COBALAMIN MALABSORPTION ( IMERSLUNDS SYNDROME ) RARE
D. COMPETITION FOR COBALAMIN
* FISH TAPEWORM( DIPHYLLOBOTHRIUM LATUM )
* BACTERIA - BLIND LOOP SYNDROME
E. DRUGS - PARA AMINO SALICYLIC ACID, COLCHICINE, NEOMYCIN
3. OTHERS
* NITROUS OXIDE
* TRANSCOBALAMIN II DEFICIENCY ( RARE)
* CONGENITAL ENZYME DEFECTS ( RARE )
FOLIC ACID DEFICIENCY
1. INADEQUATE INTAKE - UNBALANCED DIET ( COMMON IN ALCOHOLICS, TEENAGERS, SOME INFANTS )
2. INCREASED REQUIREMENTS
* PREGNANCY
* MALIGNANCY
* INCREASED HAEMATOPOIESIS( CHR HEMOLYTIC ANEMIA)
* CHR EXFOLIATIVE SKIN DISORDERS
* HAEMODIALYSIS
3. MALABSORPTION
* TROPICAL SPRUE
* NONTROPICAL SPRUE
* DRUGS - PHENYTOIN, BARBITURATES, ETHANOL
4. IMPAIRED METABOLISM
* INHIBITORS OF DIHYDROFOLATE REDUCTASE - METHOTREXATE, PYRIMETHAMINE, TRIAMTERENE, PENTAMIDINE, TRIMETHOPRIM
* ALCOHOL
* REARE ENZYME DEFICIENCIES - DIHYDROFOLATE REDUCTASE, OTHERS
OTHER CAUSES :
1. DRUGS THAT IMPAIR DNA METABOLISM
* PURINE ANTAGONISTS - 6-MERCAPTOPURINE, AZATHIOPRINE ETC
* PYRIMIDINE ANTAGONISTS - 5-FLUOROURACIL, CYTOSINE, ARABINOSIDE ETC
* OTHERS- PROCARBAZINE, HYDROXYUREA, ACYCLOVIR, ZIDOVUDINE
2. METABOLIC DISORDERS ( RARE )
* HEREDITARY OROTIC ACIDURIA
* LESCH-NYHAN SYNDROME
* OTHERS
3. MEGALOBLASTIC ANEMIA OF UNKNOWN ETIOLOGY
* REFRACTORY MEGALOBLASTIC ANEMIA
* DI GUGLIELMOS SYNDROME
* CONGENITAL DYSERYTHROPOIETIC ANEMIA
OTHER CAUSES OF MACROCYTOSIS -
* ALCOHOLISM
* HEMOLYSIS
* LIVER DISEASE
* HYPOTHYROIDISM
* APLASTIC ANEMIA
OTHER TESTS :
* MCV > 100 FL
* RETICULOCYTE , LEUKOCYTE & PLATELET COUNT - LOW
* ANISOCYTOSIS, POIKILOCYTOSIS - MARKED
* NEUTROPHILS - SHOW HYPERSEGMENTATION OF NUCLEUS ( MOST CHARECTERISTIC )
* RBC FOLATE LEVELS ARE MOST RELIABLE IN FOLATE DEFICIENCY
* SERUM METHYLMALONIC ACID & HOMOCYSTEINE LEVELS ARE HIGH IN COBALAMIN DEFICIENCY, WHILE FOLATE DEFICIENCY WILL HAVE ONLY ELEVATED HOMOCYSTEINE LEVELS.