Genodermatoses and Nevi Flashcards

Xeroderma pigmentosum results from a defect in which DNA repair pathway?

Answer: Nucleotide excision repair

Xeroderma pigmentosum is caused by defective nucleotide excision repair, impairing removal of UV-induced pyrimidine dimers.

Patients with xeroderma pigmentosum have a markedly increased risk of what cutaneous complication?

Answer: Early skin cancers on sun-exposed skin

Impaired repair of UV damage leads to numerous early basal cell carcinomas, squamous cell carcinomas, and melanomas.

Incontinentia pigmenti follows which inheritance pattern and is usually lethal in males?

Answer: X-linked dominant

Incontinentia pigmenti (IKBKG/NEMO mutation) is X-linked dominant and typically lethal in affected males in utero.

The four sequential stages of incontinentia pigmenti (vesicular, verrucous, hyperpigmented, hypopigmented) follow what distribution?

Answer: Lines of Blaschko

The cutaneous lesions of incontinentia pigmenti evolve along the lines of Blaschko reflecting mosaicism.

A port-wine stain in the V1 trigeminal distribution with leptomeningeal angiomatosis suggests which syndrome?

Answer: Sturge-Weber syndrome

Sturge-Weber syndrome combines a facial capillary malformation (port-wine stain) with ipsilateral leptomeningeal and ocular vascular anomalies.

Sturge-Weber syndrome and isolated port-wine stains are associated with somatic mosaic mutations in which gene?

Answer: GNAQ

Somatic activating GNAQ (p.R183Q) mutations underlie both Sturge-Weber syndrome and nonsyndromic port-wine stains.

Epidermolysis bullosa simplex most commonly results from mutations in which structural proteins?

Answer: Keratins 5 and 14

EB simplex is usually caused by mutations in keratin 5 or keratin 14 within basal keratinocytes, producing intraepidermal cleavage.