Abstract | March 24, 2024
Dystrophinopathy vs. Idiopathic Inflammatory Myopathy: A Winding Road to Neuromuscular Diagnosis
Learning Objectives
- Exemplify and detail the step-by-step and interdisciplinary approach to neuromuscular disease diagnosis by case presentation
- Increase awareness of the often long road to neuromuscular disease diagnosis, involving an integrated approach, neurophysiological clinical expertise, nonspecific and specific laboratory markers, imaging, and tissue pathology, which may result negative during disease latency
- Patient continuity with both outpatient primary and specialist care are essential in neuromuscular disease diagnosis, understanding disease progression, and building adherence to treatment, especially after acute hospitalization
Introduction: Diagnosis of neuromuscular disorders like inflammatory myopathy (IM) and muscular dystrophy (MD) often entails a long-winded road. Many cases remain dormant until vague prodromal symptoms surface into significant muscle weakness. This prompts a myriad of diagnostic work-ups until some route to clarity is achieved. Our patient’s story continues to be a working diagnosis and here, we describe her unusual course of events in her late age of onset.
Case Presentation: A 71-year-old patient with chronic conditions comes to the emergency department with inability to swallow her medications. In the same year, she reports multiple admissions for worsening proximal shoulder-hip girdle weakness and dysphagia. We begin a multidisciplinary approach to diagnosis starting with thorough patient history, family history, and labs to exclude more common and treatable neuromuscular disorders before considering IM and MD. Elevated antinuclear antibody (ANA) titer of 1:1180 and aldolase indicate signs of immune-mediated inflammation and muscle damage, and bedside electromyography appreciates critical illness myopathy. We decide on muscle biopsy as an imperative step in myopathy categorization: limb girdle syndrome (LGS) secondary to autoimmune etiology vs. MD possibly limb girdle-type (LGMD). By day 17, the patient reaches medical and physical milestones satisfying discharge to a long-term care facility. Since biopsy would take two weeks to result, the team’s initial suspicion for IM influences decision for discharge on high-dose prednisone taper until further evaluation. Unexpectedly, the patient’s muscle biopsy argues against autoimmune etiology, and rather, increased endomysial fibrosis, fatty replacement, and significant muscle degeneration suggests dystrophy. The absence of MHC-1 sarcolemmal upregulation further invalidates inflammatory myopathy.
Working Diagnosis: Our initial suspicion leans towards possible IM. However, return of tissue biopsy suggest MD.
Management and Outcome and/or Follow-up: Following discharge, the patient begins to establish care with specialized care teams. We still recommended rheumatologic support for possibility of an undiagnosed autoimmune condition, and MD genetic testing to better understand the prognosis of her condition. There are LGMD case reports documenting subtypes with late age of onset, dysphagia, and diaphragmatic dysfunction. Though we are still hopeful in establishing a definitive diagnosis, the results to our step-by-step approach heeds a promising path to diagnosis.
References and Resources
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- Cotta A, Carvalho E, da-Cunha-Júnior AL, Paim JF, Navarro MM, Valicek J, Menezes MM, Nunes SV, Xavier Neto R, Takata RI, Vargas AP. Common recessive limb girdle muscular dystrophies differential diagnosis: why and how? Arq Neuropsiquiatr. 2014 Sep;72(9):721-34. doi: 10.1590/0004-282×20140110. PMID: 25252238.
