SHM Converge Scientific Abstract ePoster Gallery-Uncovering Advanced Inflammatory Myositis via Thenar Atrophy

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This case describes a 51-year-old woman with end-stage renal disease on hemodialysis, type 2 diabetes, and prior stroke who presented with weeks of severe upper extremity pain, swelling, and weakness. Her symptoms had already prompted multiple hospitalizations and an extensive neurologic work-up, which had been unrevealing. On exam, she had bilateral arm weakness, marked left arm tenderness, warmth, and notable right thenar atrophy.<br /><br />Initial imaging ruled out vascular and structural causes, including upper-extremity CTA, chest CT with SVC protocol, and cervical spine MRI. Laboratory studies showed markedly elevated inflammatory markers (CRP 233, ESR 120) and a mildly elevated CK (367). Because of concern for a rheumatologic process, further evaluation was pursued. MRI of both humeri demonstrated edematous signal in multiple muscle groups consistent with myositis. EMG revealed severe axonal sensorimotor polyneuropathy, and muscle biopsy showed only atrophic changes without active necrosis or myopathic damage.<br /><br />Although the clinical picture was atypical, the exam finding of thenar wasting helped trigger the diagnosis. During hospitalization, CK trended down paradoxically and aldolase was negative, findings that were not typical for active inflammatory myositis. However, the myositis antibody panel was positive for anti-Mi-2, supporting an atypical dermatomyositis presentation with advanced, “burnt-out” inflammatory disease.<br /><br />The case highlights that inflammatory myositis can present in diverse and misleading ways, especially in patients with complex comorbidities. Thenar atrophy may be a clue to advanced disease, and delayed recognition can lead to irreversible muscle wasting. Clinicians should keep inflammatory myositis in the differential for unexplained muscle pain and weakness to enable earlier diagnosis and treatment.

Asset Subtitle

Carlin L. Lockwood

Meta Tag

Author List Carlin L. Lockwood, David Beam

Category Clinical Vignettes

Concept Idiopathic Inflammatory Myositis

Concept Muscle Biopsy

Concept Irreversible Muscle Atrophy

Concept Atypical Presentation

Concept Diagnostic Imaging

Distinguished Non-Finalist

Presenter Organization University of Chicago

Presenting Author Carlin L. Lockwood

Track Adult

Keywords

end-stage renal disease

hemodialysis

type 2 diabetes

upper extremity pain

muscle weakness

myositis

dermatomyositis

anti-Mi-2

thenar atrophy

elevated inflammatory markers

Idiopathic Inflammatory Myositis

Muscle Biopsy

Irreversible Muscle Atrophy

Atypical Presentation

Diagnostic Imaging