[Hypocomplementemic urticarial vasculitis in SLE: between urticaria and autoimmunity].

Background: Urticarial vasculitis (UV) is a rare entity affecting small blood vessels, characterized by persistent (>24 hours) urticarial lesions with histopathological findings of leukocytoclastic vasculitis. It is classified as normocomplementemic (NUV) and hypocomplementemic (HUV), the latter associated with systemic diseases such as systemic lupus erythematosus (SLE). Its incidence is 0.5 per 100,000 person-years.

Case report: Clinical presentation: A 66-year-old female with a history of SLE, hypothyroidism, and osteoarthritis developed in 2022. In 2022, she developed a dermatosis disseminated to all four body segments with pruritic wheals lasting up to 72 hours, persisting for more than six weeks, and followed by post-inflammatory hyperpigmentation. No triggering factors were identified. She also presented episodes of palpebral and labial angioedema. Given the clinical features, a skin biopsy and complement measurement were performed. Imaging/laboratory studies: Skin biopsy: Superficial neutrophilic vasculitis (venulitis) with erythrocyte extravasation. Lab results 2023: C3: 79.7 mg/dL. C4: 10.8 mg/dL.

Conclusion: This case highlights the importance of considering hypocomplementemic urticarial vasculitis in patients with SLE and persistent urticarial lesions, as well as conducting a targeted history. Given the risk of systemic involvement, close follow-up and a multidisciplinary approach are essential. The diagnosis of UV requires clinical-histopathological correlation, with biopsy recommended for persistent lesions (>24 h), residual bruising, or systemic manifestations. Early identification and appropriate management are essential to prevent systemic complications. Treatment focuses on addressing underlying autoimmune diseases and managing symptoms with antihistamines, corticosteroids, or immunosuppressants, depending on the severity and systemic involvement.