A female infant develops linear vesicles on the trunk and limbs at birth, followed by verrucous streaks that resolve leaving swirling hyperpigmentation along the lines of Blaschko. She also has hypoplastic peg-shaped teeth, sparse scalp hair, and retinal vascular abnormalities. Which mode of inheritance and gene defect explains this condition?

• A X-linked recessive, mutation in the PORCN gene
• B Autosomal recessive, mutation in the SPINK5 gene
• C X-linked dominant, mutation in the IKBKG gene encoding NEMO ✓
• D Autosomal dominant, mutation in the KRT17 gene

Explanation

Incontinentia pigmenti is an X-linked dominant disorder caused by mutations in IKBKG (NEMO), lethal in males in utero, so affected liveborn patients are almost exclusively female. It progresses through four stages: linear vesiculobullous lesions, verrucous lesions, whorled hyperpigmentation along Blaschko lines, and finally atrophic hypopigmented streaks. Associated findings include pegged or hypoplastic teeth, scarring alopecia, and ocular and neurological disease. PORCN mutation causes focal dermal hypoplasia (Goltz syndrome), and SPINK5 causes Netherton syndrome.

Reference: Rook's Textbook of Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.