Hairy cell leukemia is a rare hematologic disorder predominantly affecting older men [1, 2]. It has recently been shown to be sensitive to treatment with 2-chlorodeoxyadenosine (2-CDA), with a reported 85% complete remission rate [3]. The occurrence of hairy cell leukemia in pregnancy is extremely unusual and has only been reported once previously [4].

A 23-year-old healthy, asymptomatic woman was seen in her 10th week of pregnancy for routine laboratory evaluation and was noted to have abnormal circulating lymphocytes. Her physical examination showed an enlarged and palpable spleen measuring 5 cm under the left costal margin.

A bone marrow biopsy specimen showed focal infiltrates with small lymphoid cells, which stained positive for tartrate-resistant acid phosphatase. Immunophenotyping showed a monoclonal B-cell proliferation with cross-reactivity to CD25 and CD11 consistent with hairy cell leukemia.

The patient wished to continue with her pregnancy, and treatment of her hairy cell leukemia was deferred until after delivery. She progressed normally through the pregnancy, but by the 16th week her spleen had increased significantly in size and was causing her abdominal discomfort. She subsequently had an uncomplicated splenectomy. She carried the pregnancy to term and had a normal vaginal delivery of a healthy female infant.

She breast-fed for 6 months and at the completion of breast-feeding had a 7-day course of 2-CDA. Six weeks after treatment, a repeat bone marrow biopsy specimen and aspirate were normal. Immunophenotyping showed no phenotypic evidence of residual hairy cell leukemia.

We could find no description in the medical literature of the management of this unusual blood disorder in pregnancy. Our experience suggests that patients may be allowed to continue pregnancy to term and be allowed to breast-feed before the implementation of treatment with 2-CDA without adverse effects.