Aggressive chronic lymphocytic leukemia masked by extensive marrow fibrosis

Chronic lymphocytic leukemia (CLL) is one of the most common B-cell leukemias, occurring because of abnormal proliferation of non-functional B-lymphocytes. Progressive disease is commonly complicated by anemia, thrombocytopenia, infections as well as secondary malignancies. Bone marrow fibrosis is infrequently co-occurred along with CLL. Although multiple explanations have been proposed for this association, the etiology remains unclear in most cases. Bone marrow fibrosis occurring as a complication of CLL itself, however, is a rare entity. We present an uncommon case of a patient initially diagnosed with primary myelofibrosis but later revealed to have aggressive CLL leading to bone marrow fibrosis upon re-evaluation. Treatment for CLL resolved the bone marrow fibrosis completely, confirming our suspicion of fibrosis being secondary to CLL. This sheds light on the importance of understanding the etiology of bone marrow fibrosis in patients with CLL owing to its therapeutic implications. The utility of bone marrow biopsy in not only helping understand the etiology of the fibrosis but also providing prognostic information merits reconsideration of performing it in all cases of CLL.