Coexisting Rheumatoid Arthritis and Spinal Muscular Atrophy: A Case Report.

Rheumatoid arthritis (RA) and spinal muscular atrophy (SMA) are distinct diseases with vastly different pathophysiologic origins: autoimmune and neurodegenerative, respectively. Their co-occurrence is exceedingly rare and, to our knowledge, previously unreported. We report the case of a 41-year-old female with a seven-month history of inflammatory polyarthritis and a six-year history of undiagnosed progressive proximal muscle weakness. Clinical, serological, and electrophysiological findings confirmed diagnoses of RA and SMA type 4. This unique case underscores the importance of comprehensive evaluation in adults presenting with both joint inflammation and neuromuscular weakness. It also highlights the need for multidisciplinary care and calls for further research into shared mechanisms across neurodegenerative and autoimmune diseases.