Reversal of isolated 20q deletion with vitamin B12 replacement in a patient with pernicious anaemia.

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.