D2.255 - Adult-onset Still’s disease mimicking chronic spontaneous urticaria: a case report

Chronic spontaneous urticarial is a frequently managed as a mast-cell- mediated disease, systemic autoinflammatory conditions such as adult-onset Still’s disease (AOSD). It may present as urticarial or vasculitic skin lesions, and failure to recognize key systematic inflammatory features resulting in delayed diagnosis and inappropriate management. The aim of this study is to present a case of AOSD in chronic urticaria with systemic inflammation.

We present the case of a 40-year-old woman with severe CSU diagnosed in 2022, characterized by daily pruritic wheals and a strongly positive autologous serum skin test, suggesting CSU. The disease was controlled with high-dose H1-antihistamines. Autoimmune serology was negative, and rheumatologic diseases were excluded. In early 2025, following URTI, the patient developed persistent high-grade fever, recurrent sore throat, arthralgia, myalgia, vasculitic skin lesions on the lower extremities, and recurrent urticarial eruptions. Family history was positive for rheumatoid arthritis. Laboratory findings showed marked leukocytosis (21.6×10⁹/L), elevated ESR (82 mm/h), CRP >100 mg/L, extreme hyperferritinemia (>15,000 ng/mL), elevated total IgE (753 IU/mL). ANA and ANCA were negative; specific IgE to common allergens was absent.Skin biopsy from vasculitic lesions demonstrated productive-destructive vasculitis with perivascular lymphocytic infiltration mixed with neutrophils and eosinophils and leukocytoclasia. Biopsy from urticarial lesions revealed perivascular inflammatory infiltrates composed of T lymphocytes, neutrophils, and eosinophils.

Based on Yamaguchi’s criteria the patient was diagnosed with AOSD.

High-dose intravenous methylprednisolone (1,000 mg daily for 3 days) led to regression of symptoms. Therapy was then transitioned to oral prednisolone with gradual dose reduction, resulting in stable clinical and laboratory remission over the following year.

CONCLUSION

In patients with chronic spontaneous urticaria, persistent fever, inflammatory arthralgia, vasculitis, and extreme hyperferritinemia should prompt evaluation for adult-onset Still’s disease to prevent diagnostic delay.