Comedonic nevus Q82.9

Rare, epidermal nevus of the hair follicles, characterized by grouped, mostly linearly arranged "comedone-like", symptomless follicular horny cysts.

Unknown; familial clustering of comedones nevi has been described in some families(Naevus comedonicus syndrome). In some cases defects of a thyrosine kinase receptor have been detected.

Mostly during childhood (1-10 years), but also from birth or late manifested in adulthood.

Face, also capillitium, on the trunk often segmental, on the extremities linear, also occurring on hairless body regions.

Organoid epidermal nevus manifested in linear, band-shaped or completely bizarre arrangement (Blaschko line pattern).

Usually unilateral, bizarrely limited, skin-coloured or even hyperpigmented lesion consisting of grouped, sharply defined, flat, often splatter-like, skin-coloured depressions, skin-coloured papules and nodules (epidermal cysts) and injected 0.2-0.3 cm dilated follicular openings (comedone-like) containing a black horn plug. In pronounced cases, a sieve-like pattern can be created by a glim-like formation of comedones.

This results in a knitting pattern like overall picture (see illustration).

In a few cases, comedonal nevus is a partial symptom of an epidermal nevus syndrome (see nevus , epidermal) with ispilateral cataract and bone defects as well as neurological defects (comedonal nevus syndrome as a neuro-cutaneous disease).

A variant of comedonal nevus is "epidermolytic comedonal nevus" with acantholytic areas in the surface epithelium.

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