Laboratory diagnosis rests on parietal cell antibody with or without intrinsic factor antibody, cobalamin-deficient megaloblastic anemia and elevated serum gastrin from loss of acid secretion.
Uridine monophosphate synthase deficiency (or hereditary orotic aciduria), due to biallelic mutations in UMPS, is a rare condition presenting with megaloblastic anemia in the first months of life.
Deficiency in the trifunctional enzyme containing methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase and formyltetrahydrofolate synthetase activities, has been identified in a single patient with megaloblastic anemia, atypical hemolytic uremic syndrome and severe combined immune deficiency.
Complete absence of TC-II or total functional abnormality causes tissue vitamin B12 deficiency resulting in a severe disease with megaloblastic anemia and immunologic and intestinal abnormalities in the first months of life.
Hyperhomocysteinemia, hypomethioninemia, low serum folate concentration, and an absence of megaloblastic anemia were consistent with the diagnosis of methylenetetrahydrofolate reductase (MTHFR) deficiency.
The folate disorder selected for illustration, methylenetetrahydrofolate reductase (MTHFR) deficiency, paradoxically causes neurological problems but no megaloblastic anemia.
We report the lack of megaloblastic anaemia in a patient with severe methionine synthase deficiency who is also homozygous for C677T in MTHFR, hypothesize that the MTHFR polymorphism protects the patient against anaemia and speculate that homozygosity for MTHFRC677T could cause the dissociation between haematological and neurological disease seen in some patients with vitamin B12 deficiency.
Interaction between methionine synthase isoforms and MMACHC: characterization in cblG-variant, cblG and cblC inherited causes of megaloblastic anaemia.
Patients of the cblE complementation group of disorders of folate/cobalamin metabolism who are defective in reductive activation of methionine synthase exhibit megaloblastic anemia, developmental delay, hyperhomocysteinemia, and hypomethioninemia.
Methylenetetrahydrofolate dehydrogenase (MTHFD1) deficiency has recently been reported to cause a folate-responsive syndrome displaying a phenotype that includes megaloblastic anemia and severe combined immunodeficiency.
Methionine synthase reductase (MTRR) is the locus of the cblE class of inborn errors of cobalamin metabolism that is characterized by megaloblastic anemia and homocystinuria.