The concurrent association of inflammatory polymyositis and Crohn’s ileo-colitis in a Sri Lankan man: a case report of a rare association and literature review

BACKGROUND Crohn's disease is a relapsing, systemic inflammatory disease affecting the gastrointestinal tract with associated extraintestinal manifestations and immune disorders. Among the few cases reported, the association of Crohn's disease with polymyositis varies in its complexity and severity. We report here the first known case of inflammatory polymyositis leading to rhabdomyolysis in a male patient diagnosed with Crohn's ileocolitis. CASE PRESENTATION A 42-year-old previously healthy man presented with acute polymyositis leading to rhabdomyolysis. The acute nature of the illness raised the suspicion of an infective, toxic, or metabolic insult, which was excluded during further investigations. Prolonged low-grade fever and raised inflammatory markers led to the suspicion of inflammatory polymyositis, which was confirmed by electromyography and muscle histology. In the absence of an infective cause, the concurrent association of prolonged diarrhea containing blood and mucous after recovery from an acute phase of myositis proved a diagnostic challenge. Ileocolonoscopy findings of extensive aphthous ulceration with skip lesions extending to the terminal ileum, and histology showing polymorph infiltration of the lamina propria, transmural involvement, and micro abscess formation was suggestive of Crohn's disease. Sensory motor axonal peripheral neuropathy, which is another rare association of inflammatory bowel disease, was also present. CONCLUSION An unrecognized genetic predisposition or altered gut permeability causing disruption of the gut immune barrier triggering an immune response against skeletal muscles may have contributed to this unique association. Both polymyositis and Crohn's ileocolitis responded well to corticosteroids and azathioprine, which is supportive of their immune pathogenesis. Myositis can be considered to be a rare extraintestinal manifestation of Crohn's disease and can be used in the differential diagnosis of corticosteroid or hypokalemia-induced myopathy in Crohn's disease.