SHM Converge Scientific Abstract ePoster Gallery-Paraneoplastic Unilateral Ulnar Neuropathy Secondary to Smoldering Multiple Myeloma

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This case report describes a 74-year-old man with a history of MGUS who developed progressive right upper extremity weakness in an ulnar nerve distribution, with muscle wasting in the hand. Initial orthopedic evaluation and imaging were unrevealing. Further workup showed an elevated kappa/lambda ratio, M-spike, increased IgG, and bone marrow biopsy with 20–30% plasma cells. PET/CT, MRI of the arm, fat pad biopsy for amyloidosis, and a paraneoplastic antibody panel were negative, while EMG showed a marked reduction in motor amplitude.<br /><br />Because he had marrow plasmacytosis without CRAB features, he was diagnosed with smoldering multiple myeloma. Clinicians suspected a paraneoplastic neurologic syndrome causing the unilateral ulnar neuropathy. He was treated with DRVd therapy: daratumumab/hyaluronidase, lenalidomide, bortezomib, and dexamethasone. After four months, his IgG and kappa protein levels improved, repeat bone marrow biopsy showed only 4% plasma cells, and his motor neuropathy completely resolved.<br /><br />The report emphasizes that paraneoplastic neurologic syndromes are rare but should be considered when unexplained neurologic deficits occur in a patient with malignancy, especially when imaging does not identify another cause. These syndromes may arise through tumor-related secretions or immune cross-reactivity. Peripheral nerve involvement can cause sensory, motor, or mixed neuropathies, though purely sensory presentations are most common.<br /><br />The main takeaway is that neurologic symptoms may improve or resolve when the underlying malignancy is treated, making early recognition and treatment important.

Asset Subtitle

Benjamin J. Behers

Meta Tag

Author List Anjan Patel, Benjamin J. Behers, Elora Friar, Kabir Grewal

Category Clinical Vignettes

Concept Paraneoplastic Neurologic Syndrome

Concept Ulnar Nerve Compression

Concept Monoclonal Gammopathy

Concept Smoldering Multiple Myeloma

Concept Multiple Myeloma

Distinguished Non-Finalist

Presenter Organization Florida State University College of Medicine

Presenting Author Benjamin J. Behers

Track Adult

Keywords

MGUS

smoldering multiple myeloma

paraneoplastic neurologic syndrome

ulnar neuropathy

motor weakness

plasma cells

bone marrow biopsy

daratumumab

lenalidomide

bortezomib

Paraneoplastic Neurologic Syndrome

Ulnar Nerve Compression

Monoclonal Gammopathy

Smoldering Multiple Myeloma

Multiple Myeloma