Polymyositis in solid organ transplant recipients receiving tacrolimus

Area of Science:

• Immunology
• Neurology
• Transplantation Medicine

Background:

• Tacrolimus (FK506) is a crucial immunosuppressant for preventing organ transplant rejection and managing autoimmune diseases.
• Solid organ transplantation recipients often require long-term immunosuppression to prevent graft rejection.

Observation:

• Two male patients, post-liver and kidney transplantation respectively, developed myopathy during tacrolimus therapy.
• Clinical and laboratory findings indicated myopathy, confirmed by muscle biopsies showing features of polymyositis.

Findings:

• Muscle biopsies revealed inflammatory myopathy with CD8+ T cell infiltration, CD68+ macrophages, and MHC class I upregulation.
• Exclusion of other causes strongly suggests tacrolimus toxicity as the etiology of polymyositis in these patients.

Implications:

• Tacrolimus-induced polymyositis is a potential adverse effect in transplant recipients.
• Routine monitoring of serum creatine kinase (CK) and clinical signs of muscle disease is advised for patients on tacrolimus.
• This highlights the importance of recognizing drug-induced myopathies in immunosuppressed populations.