Transcobalamin II deficiency associated with unusual bone marrow findings and chromosomal abnormalities.

A female infant presented at seven weeks of age with failure to thrive, progressively severe pancytopenia, hypogammaglobulinemia and, mucosal ulceration. Bone marrow morphology showed severed megaloblastic changes in the myeloid series with a shift to the left and an increased number of blasts with abnormal morphology. Erythroid precursors and megakaryocytes were markedly decreased. Cytogenetic studies showed marked aneuploidy and increased chromosomal breakage. Treatment with high doses of vitamin B12 resulted in a dramatic clinical response with hematological values becoming normal. The patient's serum showed absence of transcobalamin II, and very little TC I and TC III binding. The patient's parents had only half the lower limits of normal transcobalamin II. QUSO G-32 was used for separation of transcobalamins, and the results were confirmed by Sephacryl S-300. This case illustrates the usefulness of QUSO in the rapid diagnosis of transcobalamin II deficiency.