Dowling-Degos — SCE Dermatology MCQ

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HardInflammatory DermatosesDowling-DegosSCE Dermatology

A woman has progressive reticulate flexural pigmentation, comedone-like lesions on the neck and pitted perioral scars. Biopsy shows elongated branching rete ridges with increased basal pigmentation. Which gene is the classic cause?

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Correct answer: A — KRT5 encoding basal keratin 5

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

B is correct. The combination of adult-onset reticulate flexural pigmentation, comedone-like lesions and pitted perioral scars is classic Dowling-Degos disease. The common classic form is autosomal dominant and caused by loss-of-function variants in KRT5, encoding keratin 5; genetically related reticulate-pigmentation phenotypes may involve POFUT1, POGLUT1 or PSENEN. ATP2A2 causes Darier disease, ABCC6 causes pseudoxanthoma elasticum, FERMT1 causes Kindler epidermolysis bullosa and PTCH1 is associated with Gorlin syndrome. The replacement removes the original duplicated KRT5 alternatives and makes each distractor a parallel gene-disease association.

Reference: DermNet Dowling-Degos disease pathology: https://dermnetnz.org/topics/dowling-degos-disease-pathology