D1.385 - Lamotrigine-induced Stevens-Johnson syndrome in a pediatric patient with Takayasu arteritis: the steroid paradox

Introduction. Stevens-Johnson syndrome (SJS) is a severe cutaneous adverse reaction characterized by epidermal necrosis and mucosal detachment. Management of SJS is exceedingly complex in patients with comorbid conditions requiring multicomponent systemic therapy. We present a rare case of lamotrigine-induced SJS in a 9-year-old girl with Takayasu arteritis (TA) and generalized epilepsy, which occurred paradoxically against the background of high-dose corticosteroid therapy.

Case Description. A 9-year-old female with generalized idiopathic epilepsy and newly diagnosed Takayasu arteritis received vasculitis treatment involving methylprednisolone pulse therapy followed by oral glucocorticosteroids. Concurrently, a switch in antiepileptic therapy was initiated from valproic acid and levetiracetam to lamotrigine. Shortly after initiating lamotrigine, despite ongoing systemic corticosteroids, she developed generalized maculopapular exanthema that rapidly evolved into SJS affecting <30% of body surface area. Laboratory findings showed elevated C-reactive protein (96 mg/L) and D-dimer (182.9 ng/mL). Following combined therapy for TA and SJS, both clinical condition and laboratory levels normalized.

Discussion. This case illustrates the "steroid paradox" in severe cutaneous reactions: systemic corticosteroids do not invariably prevent drug hypersensitivity and may mask early prodromal symptoms. The transition from valproic acid to lamotrigine represents a high-risk period due to valproate-mediated inhibition of glucuronidation (enzyme UGT1A4), prolonging lamotrigine clearance. Given these risks, modification of the titration schedule is recommended. Management required a complex balance: immediate withdrawal of lamotrigine while maintaining immunosuppression. The condition was stabilized with corticosteroids, cyclophosphamide (underscoring the distinction between immunopathogenic pathways of vasculitis (Th1/Th17) and SJS (CD8+/Granulysin)), and topical skin care (Bacillus-containing agents).

Conclusion. Systemic corticosteroid therapy in comorbid pediatric patients should not diminish vigilance for severe drug reactions. This case highlights the need for cautious anticonvulsant titration—considering enzyme inhibitor "washout"—and a multidisciplinary approach to balance managing drug allergy and systemic vasculitis.

Consent. Written informed consent was obtained from the patient's parents for the publication of clinical data.