Linear IgA Disease — SCE Dermatology MCQ

Correct answer: E — Dapsone

The correct answer is E, Dapsone. This child has chronic bullous disease of childhood (linear IgA disease), the diagnosis established by the characteristic annular vesiculobullous eruption in a string of pearls or cluster of jewels pattern, the antecedent infective trigger, and linear IgA deposition along the basement membrane zone on direct immunofluorescence. Dapsone is considered the first-line therapy with prompt response from most patients, working via inhibition of neutrophil chemotaxis and myeloperoxidase activity, which underlies the neutrophil-rich subepidermal blistering in this condition. Before starting, G6PD status and baseline full blood count must be checked, as dapsone causes dose-dependent haemolysis and can precipitate severe haemolytic anaemia in G6PD deficiency, with regular monitoring thereafter. Why the other options are wrong: C. Rituximab: reserved for severe, refractory linear IgA disease unresponsive to dapsone and other conventional agents, not appropriate as initial therapy given its cost, immunosuppressive risk profile and lack of first-line evidence in children. B. Azathioprine: used as a steroid-sparing adjunct in resistant or relapsing disease, but has a slower onset of action and is not the initial agent of choice when dapsone is usually effective and better tolerated in children. D. Topical Clobetasol alone: potent topical steroids may help localised or mild disease but do not adequately control the widespread vesiculobullous eruption described, and monotherapy fails to address the systemic immune-mediated process. A. Oral Prednisolone: systemic steroids can be used as an adjunct or in dapsone-intolerant patients, but carry significant paediatric adverse effects (growth suppression, adrenal suppression) making them inferior to dapsone as first-line therapy, and steroid alone is often less effective at achieving disease control. Key point: The string of pearls sign with linear IgA on DIF confirms chronic bullous disease of childhood, and dapsone (after excluding G6PD deficiency) is the first-line treatment of choice.

Reference: British Association of Dermatologists, Skin Health Info Patient Hub, Linear IgA disease, https://www.skinhealthinfo.org.uk/condition/linear-iga-disease/