Abstract
Vitamin B12 (cobalamin) and folic acid play a crucial role in DNA synthesis, cell division and proliferation. Their deficiency may cause serious disorders of hematopoietic, gastrointestinal and neurologic system. A 14-year-old girl, undergoing maintenance chemotherapy (methotrexate, 6-mercaptopurine) for acute lymphoblastic leukemia (ALL), presented with the complaints of pallor and nose bleeding. At admission, white blood cells (WBC) was 2230/mm3, hemoglobin 6.2 gr/dL, mean corpuscular volume (MCV) 122 fL and thrombocytes 26700/mm3. Peripheral blood smear revealed hypersegmented neutrophils, macrocytosis, anisocytosis, rare normoblasts and 4-5 platelet per field. Bone marrow aspiration and biopsy did not confirm the pre-diagnoses of relapsed ALL, hemophagocytic lymphohistiocytosis (HLH) and myelodysplastic syndrome (MDS). Vitamin B12 and folic acid were prescribed after obtaining the results of vitamin B12 (587 pg/mL), folic acid (1.3 ng/mL) and homocystein (21 µmol/L). Folic acid deficiency must be kept in mind in childrenwith ALL receiving maintenance therapy. Serum cobalamin and folic acid levels must be checked in case of unexplained pancytopenia.