What provokes megaloblastic anemia?

There are following reasons for the development of megaloblastic anemia.

Deficiency of vitamin B ₁₂ :

Alimentary deficiency (vitamin B ₁₂ <2 mg / day, vitamin B ₁₂ deficiency in the mother, resulting in a reduced vitamin B ₁₂ content in breast milk);

Violations of absorption of vitamin B ₁₂ :

• Inadequacy of the internal factor (Castle factor):
  • pernicious anemia;
  • surgical intervention on the stomach:
  • total gastrectomy;
  • partial gastrectomy;
  • gastric bypass;
  • action of caustic substances;
• functional anomaly of internal factor;
• biological competition:
  • excess bacterial growth in the small intestine;
  • anastamosis and fistula;
  • blind loops and pockets;
  • strictures;
  • scleroderma;
  • achlorhydria;
  • helminths (Diphylobothrium latum);
• infringements of a suction in an ileum:
  • family selective impairment of absorption of vitamin B ₁₂ (Imerslund-Gresbek syndrome);
  • drug-induced violation of absorption of vitamin B ₁₂;
  • chronic diseases of the pancreas;
  • Zollinger-Ellison syndrome;
  • hemodialysis;
  • diseases affecting the ileum:
  • resection and shunt of the ileum;
  • local enteritis;
  • celiac disease;

Disorders in the transport of vitamin B ₁₂ :

• hereditary deficiency of transcobalamin II;
• transitory deficiency of transcobalamin II;
• partial deficiency of transcobalamin I;

Metabolic disorders of vitamin B ₁₂ :

• hereditary:
  • deficiency of adenosylcobalamin;
  • deficiency of methyl malonyl-CoA mutase (muf, mut);
  • combined deficiency of methylcobalamin and adenosylcobalamin;
  • deficiency of methyl cobalamin;
• purchased:
  • liver disease;
  • protein deficiency (kwashiorkor, marasmus);
  • Drug-induced (eg, aminosalicylic acid, colchicine, neomycin, ethanol, oral contraceptives, metformin).

Deficiency of folate:

• alimentary deficiency;
• increased need:
  • alcoholism and cirrhosis of the liver;
  • pregnancy;
  • newborn;
  • diseases associated with increased cell proliferation;
• congenital malabsorption of folic acid;
• drug-induced violation of absorption of folic acid;
• extensive intestinal resection, resection of jejunum.

Combined deficiency of folic acid and vitamin B ₁₂ :

• tropical sprue;
• gluten-dependent enteropathy.

Congenital DNA synthesis disorders:

• orotic aciduria;
• Lesha-Nihan syndrome;
• thiamine-dependent megaloblastic anemia;
• deficiency of enzymes necessary for the metabolism of folic acid:
  • N5-methyl-tetrahydrofolate-transferase;
  • formiminotransferase;
  • dihydrofolate reductase;
• deficiency of transcobalamin II;
• abnormal transcobalamin II;
• homocystinuria and methylmalonic aciduria.

Drug and toxin-induced DNA synthesis disorders:

• folate antagonists (methotrexate);
• Purine analogues (mercaptopurine, azathioprine, thioguanine);
• pyrimidine analogs (fluorouracil, 6-azauridine);
• inhibitors of ribonucleotide reductase (cytosine arabinoside, hydroxycarbamide);
• alkylating agents (cyclophosphamide);
• Nitric oxide;
• arsenic;
• chloroethane.

In addition, megaloblastic anemia can be caused by erythroleukemia.