Linear keratotic lesions in a young woman: JAMA
A woman in her 20s presented with linear hyperkeratotic papules on her right arm. The patient reported that these asymptomatic lesions were present since birth and did not appear to change on sun exposure or with seasons. She had no family history of a similar cutaneous feature. Physical examination revealed that these lesions were distributed in a Blaschkoid pattern.

On close inspection, numerous reddish punctate keratotic papules were observed on the patient’s right forearm that coalesced into plaques on the dorsum of her right hand. No extracutaneous abnormalities were found. A skin biopsy specimen from the patient’s right arm was obtained
Histologic examination revealed acanthosis, focal hyperkeratosis, and epidermal invagination. The eccrine ducts and ostia were hyperplastic and dilated. The parakeratotic cornoid lamellae were found on the acrosyringium.

A diagnosis of porokeratotic eccrine ostial and dermal duct nevus (PEODDN) was made based on cutaneous and characteristic histopathologic findings. The diagnosis was further confirmed through genetic testing for GJB2 (OMIM 121011), which was performed using DNA extracted from the affected epidermis and hyperplastic eccrine ducts by laser-captured microdissection. A mosaic missense mutation c.134G>A (p.Gly45Glu) in GJB2 was found. Cryotherapy was recommended, but the patient refused.

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