# When Foot Drop Tells a Bigger Story: POEMS (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal Plasma Cell Disorder, and Skin Changes) Syndrome Revealed by Femoral Plasmacytoma

## TL;DR

A case study shows how a rare condition called POEMS syndrome was diagnosed in a patient initially thought to have CIDP, emphasizing the need for thorough diagnostic approaches.

## Contribution

Highlights the diagnostic challenges of POEMS syndrome and the importance of multidisciplinary evaluation in atypical CIDP-like cases.

## Key findings

- Initial symptoms and tests suggested CIDP but further investigation revealed POEMS syndrome.
- Diagnostic confirmation came from identifying a monoclonal protein and a femoral plasmacytoma.
- The case underscores the need to consider POEMS syndrome in patients with refractory neuropathy and systemic features.

## Abstract

POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, and skin changes) syndrome is a rare multisystem disorder caused by a monoclonal plasma cell dyscrasia, often presenting with a constellation of neuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes. Its initial manifestations frequently overlap with more common causes of chronic progressive neuropathy, such as chronic inflammatory demyelinating polyneuropathy (CIDP) and diabetic or paraproteinemic neuropathies, which can obscure the diagnosis and delay definitive treatment. We report a 45-year-old male with progressive bilateral lower-limb distal-predominant weakness and numbness over three months, in whom the clinical picture and cerebrospinal fluid findings initially supported a working diagnosis of CIDP, despite coexisting thrombocytosis, skin hyperpigmentation, and newly diagnosed diabetes mellitus. Electroneuromyography showed severe sensorimotor mixed axonal and demyelinating neuropathy, and cerebrospinal fluid analysis demonstrated albuminocytologic dissociation, further reinforcing the initial impression of CIDP and illustrating the diagnostic conflict. However, serum studies identified an IgA lambda monoclonal protein, and fluorodeoxyglucose positron emission tomography revealed a solitary, metabolically active lesion in the right femur, raising suspicion for an underlying plasma cell dyscrasia rather than isolated inflammatory neuropathy. Histopathological examination of the femoral lesion confirmed a lambda-restricted plasmacytoma with minimal bone marrow plasma cell infiltration, fulfilling the diagnostic criteria for POEMS syndrome in conjunction with polyneuropathy, monoclonal plasma cell disorder, plasmacytoma, thrombocytosis, and skin changes. This case highlights the importance of considering POEMS syndrome in patients with atypical or treatment-refractory CIDP-like presentations and systemic features, and it underscores how a stepwise, multidisciplinary diagnostic approach incorporating electrophysiology, advanced imaging, and targeted histopathology can resolve overlapping differentials and guide timely, targeted therapy