A case of Erdheim-Chester disease who has policythemia vera

Erdheim-Chester disease (ECD) is a rare disease that is characterized by multi-organ involvement of foamy histiocytes. It causes systemic inflammation, and also demonstrates various clinical manifestations and has a poor prognosis. We encountered a case of ECD in a patient that had been treated for underlying polycythemia vera. As far as we know, this is the first reported case worldwide where ECD developed in association with polycythemia vera. A 59-year-old man visited our hospital due to pleuric pain at the right side of the chest. Pleural tissue that was obtained following a thoracoscopic biopsy showed non-Langerhan's cell histiocytosis, suggesting the presence of ECD. The histiocytes stained positively for CD68, but were negative for S-100 and CD1a. The patient also complained of pain at both hips and the right shoulder area. An X-ray and magnetic resonance image demonstrated that the lesion showed sclerosis and osteolysis in both the proximal femur and right humerus. Treatment was started with predinisolone, and subsequently cyclophosphamide was added. ECD is a very rare multi-systemic disease, and its cause and therapeutic options have not yet been defined. ECD has a poor prognosis. Therefore, we believe that additional case studies are needed prior to the determination of a novel therapy for ECD.