Adult-onset Still's disease presenting with periorbital erythematous rash and progressive interstitial lung disease.

A man in his 80s with chronic obstructive pulmonary disease presented with fever, arthralgia and periorbital erythema resembling a heliotrope rash, accompanied by progressive interstitial lung disease (ILD). Laboratory investigations revealed neutrophilic leucocytosis and markedly elevated C-reactive protein, ferritin and Krebs von den Lungen-6. Dermatomyositis, particularly clinically amyopathic dermatomyositis, was considered in the differential diagnosis; however, myositis-specific autoantibodies were negative and histopathological findings supported a diagnosis of adult-onset Still's disease (AOSD). Despite the high-dose corticosteroids and ciclosporin, lung disease progressed to respiratory failure. Treatment with tocilizumab led to clinical and radiological remission with normalisation of inflammatory markers.This case highlights that AOSD can present with rapidly progressive ILD and closely mimic dermatomyositis, underscoring the importance of careful differential diagnosis and timely cytokine-targeted therapy.