Summary

Severe vitamin B₁₂ deficiency is well known to cause morphological alterations in bone marrow. In rare instances, these myelodysplastic and megaloblastic changes can coexist with cytogenetic abnormalities. Here, we report a case of a 38-year-old African-American woman with pernicious anaemia, who was found to have an isolated 20q deletion and which resolved after vitamin B₁₂ replacement. We also discuss various mechanisms in which vitamin B₁₂ deficiency can lead to chromosomal abnormalities. A literature review is also performed to evaluate various other chromosomal aberrations associated with B₁₂ deficiency.