Case Report: Myelodysplastic changes and 7q deletion in a case of vitamin B12 deficiency: a diagnostic pitfall

Vitamin B12 plays a crucial role in DNA synthesis, and its deficiency can occasionally present with atypical hematological manifestations mimicking myelodysplastic syndrome (MDS). There is limited literature describing reversible chromosomal abnormalities associated with vitamin B12 deficiency. We report an 11-year-old girl who presented with generalized body aches for 1 month and fever, easy fatigability, and respiratory distress for 2 days. Examination revealed pallor and hepatomegaly, with no splenomegaly. Investigations showed severe anemia (hemoglobin 3.1 g/dL), thrombocytopenia, a low corrected reticulocyte count, and macrocytosis with macro-ovalocytes on a peripheral smear. Considering pancytopenia with congestive cardiac failure, the differential diagnoses included viral infection-induced cytopenias, leukemia, megaloblastic anemia, and MDS. Bone marrow examination demonstrated myelodysplastic changes, while cytogenetic analysis revealed a 7q deletion in 18% of metaphases. Serum vitamin B12 levels were markedly low (<83 pg./mL). The child received a packed red cell transfusion and oral vitamin B12 supplementation, following which the blood counts improved significantly. Repeat bone marrow examination after 2 months showed complete resolution of the abnormalities. Vitamin B12 deficiency can rarely lead to chromosomal abnormalities such as 7q and 20q deletions, aneuploidy, and hypoploidy because of impaired DNA synthesis and uracil misincorporation into DNA strands. Such abnormalities are classically associated with MDS and acute myeloid leukemia, potentially leading to diagnostic confusion and unnecessary aggressive treatment. Recognition of vitamin B12 deficiency as a reversible cause of dysplastic marrow changes and cytogenetic abnormalities is therefore essential. Early identification and prompt treatment can result in complete hematological and cytogenetic recovery.