SHM Converge Scientific Abstract ePoster Gallery-Unmasking Anca-Associated Vasculitis With Myopathy: An Unusual Cause of Weakness

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This case describes an unusual presentation of ANCA-associated vasculitis (AAV) with myopathy in an 80-year-old man with newly diagnosed pulmonary fibrosis who developed 6 weeks of ascending bilateral leg pain and weakness. His symptoms began in the feet and calves and progressed to the thighs, becoming severe enough that he could no longer walk without assistance. He also had fever, night sweats, weight loss, and dyspnea on exertion. Examination showed warm legs with intact pulses, marked allodynia/hyperalgesia, and distal weakness influenced by pain. Initial labs revealed inflammatory markers and leukocytosis, but normal CK, ANA, creatinine, and complement levels.<br /><br />Because his presentation was subacute and inflammatory, the differential included infection, Guillain-Barré syndrome, inflammatory myositis, small vessel vasculitis, spinal disease, malignancy, paraneoplastic syndromes, and neuromuscular junction disorders. MRI of the brain and spine, CT chest/abdomen/pelvis, and CSF studies were unrevealing. EMG suggested subtle myopathic changes, and MRI of the thighs showed diffuse intramuscular edema. Muscle biopsy of the right vastus lateralis demonstrated necrotizing vasculitis and denervation. Serology was positive for MPO-ANCA, confirming AAV with myopathy.<br /><br />The case highlights that AAV with myopathy can present as subacute lower-extremity pain and weakness, often with normal CK, and is especially important to consider in older hospitalized patients. Early recognition is critical because it can mimic claudication, inflammatory myositis, neuropathy, or other neurologic disorders. The patient improved after induction with systemic steroids and later maintenance rituximab.

Asset Subtitle

Prashant Patel

Meta Tag

Author List Brandon Scott, Maham Awan, Prashant Patel

Category Clinical Vignettes

Concept Subacute Weakness

Concept ANCA-Associated Vasculitis

Concept Bilateral Lower-Extremity Pain

Concept Myopathy

Concept Creatine Kinase

Distinguished Non-Finalist

Presenter Organization Univeristy of California, San Francisco

Presenting Author Prashant Patel

Track Adult

Keywords

ANCA-associated vasculitis

myopathy

MPO-ANCA

muscle biopsy

necrotizing vasculitis

ascending leg weakness

allodynia

pulmonary fibrosis

normal creatine kinase

rituximab

Subacute Weakness

ANCA-Associated Vasculitis

Bilateral Lower-Extremity Pain

Myopathy

Creatine Kinase