An unusual histiocytic disorder responding to cyclosporine therapy: a case report.

PURPOSE: To describe the clinical and pathologic presentation and course of a 7-week-old girl with anemia, thrombocytopenia, and organomegaly who was found to have a histiocytic disorder distinct from previously reported cases. METHODS: Bone marrow specimens were studied with conventional methods. A liver biopsy specimen was evaluated by routine and immunohistochemical methods and electron microscopy. RESULTS: The patient was found to have a unique histiocytic disorder in which lesional cells displayed an atypical phenotype. Cyclosporine therapy was associated with a prompt, complete, and apparently permanent resolution of disease. CONCLUSION: This case appears to represent an atypical histiocytic disorder with unique clinical and pathologic features. The disorder resolved after the initiation of cyclosporine therapy.