Abstract

We diagnosed to the patient as primary mediastinal CD20 positive diffuse large B-cell lymphoma two years ago. The patient received R-CHOP chemotherapy. Complete remission was obtained from chemotherapy. After 18 months, headache, nausea and vomiting occurred. Cranial magnetic resonance imaging showed mass lesions. Cranial radiotherapy was applied. Then intrathecal methotrexate (MTX) was administered at a dose of 12 mg via lumbar puncture twice weekly for 6 weeks. Pancytopenia was detected after ten days of the discontinuation of intrathecal MTX. There were apparent megaloblastic changes on the bone marrow aspiration and biopsy. The biochemical parameters were folic acid 6.22 ng/ml (N:4.2-19.99) and cobalamin 803 pg/ml (N:197-866). The patient was treated with oral folic acid 5 mg/day. Hematological parameters were hemoglobin 10.2 g/ dl, platelet count 432 000/mm3, and leukocyte count 5100/mm3 at the 14th day. In conclusion, the patients treated with intrathecal MTX should be followed-up and folic acid prophylaxis may be considered.