A case of systemic mastocytosis mimicking POEMS syndrome: A case report.

RATIONALE: POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) syndrome is a rare and complicated disease related to multiple organs and systems. Here, we report a case of systemic mastocytosis (SM) that was misdiagnosed as a POEMS syndrome. PATIENT CONCERNS: A 42-year-old man presented with skin changes, diarrhea, and limb numbness. DIAGNOSES: Positron emission tomography/computed tomography revealed extravascular volume overload, organomegaly, lymphadenopathy, and bone lesions with mixed lesions of osteosclerosis and osteolysis. Therefore, POEMS syndrome was suspected. Further histopathological and immunohistochemical examination of the bone marrow, lymph nodes, and gastric mucosa suggested a diagnosis of mastocytosis. The c-Kit D816V mutation confirmed the diagnosis of SM. INTERVENTIONS: The patient received the treatment of pegylated interferon-alpha weekly and glucocorticoid daily. OUTCOMES: The symptoms relieved significantly. LESSONS: There are many similar features between POEMS syndrome and SM, probably leading to misdiagnosis. This study analyzed the different points between them which can provide help for differentiation.