A 2-year-old child presents with hyperkeratotic plaques over joints, palmoplantar keratoderma, and ichthyosis. Electron microscopy of the skin shows abnormal tonofilament aggregates within keratinocytes. The most likely diagnosis is:

• A Ichthyosis vulgaris — filaggrin gene mutation
• B Lamellar ichthyosis — transglutaminase-1 gene mutation
• C X-linked ichthyosis — steroid sulfatase deficiency
• D Epidermolytic ichthyosis (bullous congenital ichthyosiform erythroderma) — keratin 1 and 10 mutations ✓

Explanation

Epidermolytic ichthyosis (formerly bullous CIE) is caused by mutations in keratin 1 (KRT1) or keratin 10 (KRT10) genes. Histopathology shows epidermolytic hyperkeratosis: vacuolation of spinous/granular cells with clumped keratin filament aggregates (tonofilament clumps) visible on electron microscopy. At birth, affected neonates develop widespread blistering (mimicking epidermolysis bullosa) that evolves into brown hyperkeratosis over joint areas. Ichthyosis vulgaris shows absent/reduced keratohyalin granules on EM. Lamellar ichthyosis shows normal EM with increased TGM1 granules.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.