Refractory skin ulcers and afebrile bacteraemia with <i>Staphylococcus aureus</i> in antimelanoma differentiation-associated gene 5 antibody-positive dermatomyositis: A case report

Skin ulcers sometimes appear in patients with antimelanoma differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis (DM) and are usually associated with disease activity. Here, we report a case of a 41-year-old woman with anti-MDA5 antibody-positive DM, who developed refractory skin ulcers during the remission induction therapy, which were proven to be associated with clinically silent Staphylococcus aureus bacteraemia with septic thrombi in her lung. The patient was referred to our hospital for the treatment of amyopathic DM with interstitial lung disease. Anti-MDA5-positive DM was diagnosed, and she was treated with triple therapy combined with tofacitinib because poor prognostic factors existed. Although the remission induction therapy improved most of the symptoms, she developed erythematous rashes with ulcers on her left auricle and forearm, which were refractory to topical immunosuppressive medications. Despite the absence of systemic symptoms or elevated inflammatory markers, blood and wound cultures revealed S. aureus, and a new cavitary lesion was detected in her left lung. Subsequent antibiotic therapy resolved both the cutaneous and pulmonary lesions. This case highlights the importance of considering bacteraemia and performing blood cultures when DM-related skin ulcers resist conventional treatments, even without fever during immunosuppressive therapy.