Idiopathic polymyositis in renal transplant recipient: a case report and review of literature

Introduction and aim Myositis is a rare complication following renal transplant and is most commonly the result of a drug-mediated myotoxicity, but the idiopathic cause is still the most common. After kidney transplant, the differential diagnosis of polymyositis includes autoimmune disease, drug-induced viral infections, and rhabdomyolysis associated with electrolyte imbalance. We aimed to report a case of idiopathic polymyositis in a renal transplant recipient and review the literature for similar cases. Case report A 31-year-old male patient developed polymyositis three years following live-related kidney transplantation. Electromyography confirmed myopathic changes. The clinical features and course, MRI findings, electromyography features, positive anti-MI-2 antibody, and the response to high-dose steroid therapy are matched with immune-mediated acute polymyositis, especially after excluding viral infections and drug-induced myopathy. Conclusion Acute polymyositis may occur after a kidney transplant. Possible mechanisms include viral antigen transmission or a localized graft versus host disease. Muscle biopsy is not mandatory before prompt initiation of high-dose steroid therapy, which leads to clinical and biochemical recovery.