Abstract: Ankylosing spondylitis is predominantly driven by Th17-type immune responses. Secukinumab, a targeted agent against IL-17A, is a commonly used therapeutic drug for this condition. However, such agents may induce immune drift and trigger atopic dermatitis mediated mainly by Th2 inflammation. This article reports a 54-year-old female patient with ankylosing spondylitis. After regular treatment with secukinumab, her articular symptoms improved, yet generalized pruritic erythema and papules developed all over the body. Combined with laboratory examinations, skin lesion pathology and clinical manifestations, the patient was diagnosed with severe atopic dermatitis. Discontinuation of secukinumab plus topical medications and antihistamines failed to relieve symptoms. The patient was then switched to upadacitinib, a selective JAK1 inhibitor. Two months after treatment initiation, her skin rashes, pruritus, lumbodorsal pain and sacroiliac joint tenderness were markedly alleviated. The patient remained in stable condition without obvious adverse reactions during the 6-month follow-up.

Key words: atopic dermatitis, ankylosing spondylitis, upadacitinib, immune drift