Ichthyosis vulgaris — SCE Dermatology MCQ

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ModeratePaediatric and geneticsIchthyosis vulgarisSCE Dermatology

A 10-year-old boy has fine white scale on the extensor limbs, palmar hyperlinearity and a history of atopic eczema. The flexures are relatively spared, and symptoms worsen in winter. His father has similar dry skin. What is the most likely underlying cause?

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Correct answer: B — Filaggrin-related epidermal-barrier impairment

Explanation lettering: B = shown as A · E = shown as B · A = shown as C · C = shown as D · D = shown as E

E is correct. Ichthyosis vulgaris commonly reflects loss-of-function variants affecting filaggrin, an epidermal protein required for normal cornification and natural moisturising factor. Fine extensor scale, palmar hyperlinearity, flexural sparing, winter worsening, atopy and an affected parent fit this semidominant phenotype. Steroid-sulfatase deficiency causes X-linked ichthyosis, usually in boys, with larger darker scale and no palmar hyperlinearity or strong atopic association. Transglutaminase-1 deficiency causes autosomal-recessive congenital ichthyosis, often presenting at birth with a collodion membrane. Desmoglein-3 autoantibodies cause pemphigus vulgaris with mucosal erosions and flaccid blisters. ATP2A2 dysfunction causes Darier disease with greasy crusted papules in seborrhoeic sites and characteristic nail changes. The phenotype therefore localises to filaggrin-related barrier impairment rather than an autoimmune blistering or alternative cornification disorder.

Reference: DermNet ichthyosis vulgaris review: https://dermnetnz.org/topics/ichthyosis-vulgaris