Fever, joint pain, and systemic inflammation in a young adult: recognising adult-onset Still's disease.

A young man presented with recurrent high-spiking fevers, diffuse arthralgia, hepatomegaly and a transient salmon-coloured rash. Laboratory evaluation revealed leukocytosis, markedly elevated inflammatory markers and extreme hyperferritinaemia. Extensive infectious and autoimmune workups were negative. The patient met Yamaguchi criteria for adult-onset Still's disease (AOSD) and responded well to corticosteroids and biologic therapy with canakinumab. This case highlights the diagnostic complexity of AOSD and the importance of early consideration in patients with systemic inflammation and prolonged fever who have negative infectious and autoimmune testing.