Polyneuropathy, Organomegaly, Endocrinopathy, M-Protein, and Skin Changes (POEMS) Syndrome With Characteristic Muscle Biopsy Findings and Without M-Protein.

INTRODUCTION: POEMS (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal gammopathy, and Skin changes) syndrome is a rare paraneoplastic disorder driven by proinflammatory cytokines, particularly vascular endothelial growth factor (VEGF), which promotes multisystemic angiogenesis and inflammation. It is frequently misdiagnosed as Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) due to overlapping features. CASE REPORT: A 63-year-old woman was referred for presumed CIDP unresponsive to IVIG and steroids. Her clinical course was notable for 100-pound weight loss, papilledema, skin changes, thrombocytosis, thromboembolisms, hemi-diaphragmatic paralysis, organomegaly/lymphadenopathy, and negative bone marrow and lymph node biopsies. POEMS was diagnosed based on repeat electrodiagnostic testing, elevated VEGF and prolactin, and nerve/muscle biopsies showing endomysial edema and angiogenesis. Notably, no monoclonal protein (M-protein) was identified. Treatment with lenalidomide and dexamethasone resulted in significant clinical improvement. CONCLUSION: Paraprotein-negative POEMS syndrome should be considered in refractory CIDP, especially in the presence of skin changes, endocrinopathy, papilledema, and thrombocytosis. VEGF levels and nerve/muscle biopsy findings are critical diagnostic tools in patients with high clinical suspicion who lack monoclonal gammopathy. Muscle biopsy may increase the diagnostic yield by revealing characteristic vascular proliferation, a feature previously described in nerve biopsies of patients with POEMS syndrome.