Eosinophilia and bone lesion as clinical manifestations of aggressive systemic mastocytosis.

We report a patient with aggressive systemic mastocytosis (SM), who exhibited eosinophilia and unusual destructive bone lesions. A 43-year-old female was referred to our hospital because of a vertebral compression fracture, multiple lytic bone lesions, and eosinophilia in February 2011. A diagnosis of aggressive SM was made on the basis of abnormal mast cells in the bone marrow, high serum tryptase levels, and multiple lytic bone lesions including vertebral compression fractures. Polymerase chain reaction and subsequent sequencing of its products to identify mutations of c-kit yielded negative results and imatinib mesylate failed to improve the SM of the patient. She was then treated with interferon-α, with considerable improvement of the disease, although severe myelosuppression prevented the continued administration of a sufficient dose of this agent. In August 2011, the patient suddenly developed paraplegia of the lower extremities. Magnetic resonance imaging demonstrated epidural mass lesions at the levels from Th9 to Th11, compressing the spinal cord. Emergent laminectomy and subsequent irradiation of the tumors were performed without improvement of the paraplegia. Histopathologic examination of the epidural tumors, from samples obtained intraoperatively, confirmed the diagnosis of SM. She was further treated with dasatinib and then cladribine without obvious improvement, although the latter reduced the eosinophilia to some extent ; however, she died of sepsis in September 2011.