Introduction:

polymyositis, a relatively uncommon autoimmune disorder, develops due to abnormal activation of cytotoxic T lymphocytes and macrophages against muscle antigens presenting as a proximal myopathy is associated with interstitial lung disease in 10 to 30% of patients.

Case report:

76-year-old male with a slow evolution of eight months, characterized by fatigue, weight loss of 12 kilos, and increasing weakness in cervical paravertebral muscles and muscles of the shoulder and pelvic girdles. Laboratory showed elevated muscle enzymes, positive Anti J-1 antibodies, consistent EMG data, and a biopsy confirming polymyositis, associated with interstitial lung disease. Steroid treatment and rehabilitation were started, obtaining significant clinical improvement at three weeks.

Conclusion:

since polymyositis is not frequent, the diagnosis is reached by exclusion mainly when the symptomatology and the tomographic images coincide during COVID-19.