SHM Converge Scientific Abstract ePoster Gallery-Diagnostic Challenge of a Rare Cause of Proximal Muscle Weakness

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This case describes a 50-year-old woman with seronegative rheumatoid arthritis on upadacitinib who developed 3 weeks of generalized myalgias and progressive bilateral proximal muscle weakness, worsening despite prednisone. She had bilateral MCP erythema and no statin exposure. Initial evaluation for dermatomyositis included CT imaging, which was unremarkable, and MRI of the right lower extremity, which showed diffuse muscle atrophy without the typical T2 hyperintensity or enhancement expected in active myositis.  <br /><br />Laboratory testing was largely nondiagnostic: CK was only mildly elevated at 178 U/L, aldolase and inflammatory markers were normal, and an extensive autoimmune panel was negative. Because imaging and serologies did not explain the degree of weakness, muscle biopsy was performed. Histology showed variability in fiber size with atrophy and necrosis, along with signs of early denervation; overall findings were nonspecific but supported muscle involvement and helped exclude purely toxic or inflammatory myopathy patterns.  <br /><br />The presentation highlights rheumatoid myositis/overlap myositis as a rare and often underrecognized cause of proximal weakness in patients with rheumatoid arthritis. The key teaching point is that CK, MRI, and serologic markers may be normal or only mildly abnormal, so they are not reliable enough to rule out inflammatory muscle disease. Muscle biopsy can be crucial for diagnosis when the clinical picture remains concerning.  <br /><br />The patient ultimately improved after treatment with IV Solu-Medrol 80 mg daily and methotrexate.

Asset Subtitle

Thong Tran

Meta Tag

Author List Abu Baker Sheikh, Kenneth M. Zabel, Thong Tran

Category Clinical Vignettes

Concept Rheumatoid Myositis

Concept Proximal Muscle Weakness

Concept Inflammatory Myopathy

Concept Muscle Biopsy

Concept Rheumatoid Arthritis

Distinguished Non-Finalist

Presenter Organization University of New Mexico Health Science Center

Presenting Author Thong Tran

Track Adult

Keywords

rheumatoid arthritis

upadacitinib

proximal muscle weakness

myalgias

rheumatoid myositis

overlap myositis

muscle biopsy

creatine kinase

MRI

methotrexate

Rheumatoid Myositis

Proximal Muscle Weakness

Inflammatory Myopathy

Muscle Biopsy

Rheumatoid Arthritis