Adult-Onset Still's Disease with Dermatomyositis-Like Lesions.

Still's disease is an inflammatory disorder of unknown origin, also known as juvenile idiopathic arthritis, that predominantly affects children, as it usually appears before the age of 16. However, there is another presentation known as adult-onset Still's disease, which has a bimodal distribution with the first peak of incidence between 16 and 25 years and the second peak between 36 and 46 years. Classically, it is described as a very typical clinical picture, mainly characterised by a transient salmon-coloured rash that appears with fever spikes, typically in the evening. Additionally, most patients frequently present with symptoms such as a sore throat, generalised lymphadenopathy and hepatosplenomegaly. Less common findings include myopericarditis, interstitial lung disease, serositis and neurological involvement. However, sometimes this disease can debut with more atypical signs and symptoms, delaying diagnosis and treatment. This article describes the case of a 56-year-old Spanish patient who presented with pruritic periorbital lesions resembling the heliotrope rash of dermatomyositis but was ultimately diagnosed with adult-onset Still's disease. This case is reported so that in the presence of such cutaneous lesions, Still's disease is considered within the differential diagnosis to avoid delays in both diagnosis and treatment. LEARNING POINTS: In the early stages of adult-onset Still's disease, diagnosis can be challenging due to the lack of specific findings. In many cases, it is diagnosed by excluding other differential diagnoses.Cutaneous manifestations play a crucial role in correctly identifying the disease. The typical rash is a transient, salmon-coloured maculopapular eruption that coincides with fever spikes.However, atypical cutaneous manifestations such as dermatomyositis-like lesions, urticarial eruptions, persistent plaques, polymorphic erythema and lichenoid lesions, have been reported. These atypical skin findings may be associated with a more severe disease course, making early recognition essential for prompt diagnosis and treatment.