Adult still's disease with atypical skin manifestations: A case report

Adult Still’s Disease (ASD) is a rare, systemic, autoinflammatory disorder of unknown etiology. It is characterized by high-grade spiking fevers, arthritis, systemic inflammation, and a typical transient salmon-colored rash. However, this case report documents an atypical presentation of ASD in a 26-year-old woman, shedding light on the diagnostic complexities of the disease when classical symptoms are absent.

The patient initially presented with urticarial, erythematous, and pruritic skin lesions localized to intertriginous areas, along with generalized arthralgia. Initially misdiagnosed and treated for scabies and other infectious conditions, her condition worsened over several weeks, leading to fever, odynophagia, arthritis in the small joints and knees, and widespread dermatologic involvement. Subsequent evaluations and empirical treatments for infectious etiologies, including scarlet fever, failed to yield clinical improvement.

Laboratory testing revealed key features supportive of ASD: leukocytosis (17,000/μL) with 85% neutrophils, markedly elevated CRP (148 mg/L), ESR (95 mm/hr), and hyperferritinemia (>2000 ng/mL), alongside negative RF and ANA tests. The absence of infectious agents and the fulfillment of five Yamaguchi criteria led clinicians to consider ASD as the most likely diagnosis. Although skin biopsy was not performed due to its limited utility in ASD, imaging revealed splenomegaly and lymphadenopathy, further supporting the diagnosis.

Treatment was initiated with prednisone, followed by methotrexate as a steroid-sparing agent. The patient responded well, with significant symptom resolution. This case underscores the diagnostic challenge posed by atypical cutaneous manifestations such as urticaria and angioedema, which are infrequent but increasingly recognized variants of ASD.

The discussion emphasizes the utility and limitations of Yamaguchi’s criteria, which, while sensitive, are not disease-specific and overlap with other rheumatologic and infectious conditions. ASD should be included in the differential diagnosis when patients present with systemic inflammatory symptoms and persistent, non-specific dermatologic findings. Early recognition and timely treatment are crucial to prevent complications like macrophage activation syndrome and to reduce unnecessary testing and misdirected therapies.

In conclusion, this report highlights the importance of maintaining a high index of suspicion for ASD in patients with atypical skin presentations. It reinforces the clinical value of comprehensive evaluation, appropriate laboratory testing, and therapeutic responsiveness as diagnostic tools in cases where histopathological confirmation is limited. The successful use of methotrexate further validates its role in managing refractory or steroid-dependent ASD cases.