Track

Case Reports

Abstract

Porokeratotic Adnexal Ostial Nevus (PAON) is a rare disorder of keratinization that to date has been reported to affect eccrine and follicular adnexa.  Therefore, the term PAON was proposed in 2009 by Goddard DS, et al. as a unifying term for two previously reported entities: porokeratotic eccrine ostial and dermal duct nevus and porokeratotic eccrine and hair follicle nevus.   PAON has a wide clinical presentation ranging from asymptomatic keratotic papules and plaques to verrucous lesions.  The lesions may be mildly pruritic and occur on the acral extremities as linear punctate pits. In most cases, PAON is present at birth but, in rare cases, can present in adulthood. Unlike linear porokeratosis, PAON affects adnexae and lacks a raised ridge at the clinical edge of lesional skin.  We report a case of PAON present for as long as the patient could recall that caused the nail to split in adulthood.  Clinicopathologic correlation including intraoperative photos revealed the lesion to involve contiguous nail bed, matrix, eponychium, proximal nail fold and dorsal digit including eccrine ducts.  Intraoperative photographs and clinicopathologic correlation in this case provide further support for the use of the unifying term PAON when contributing cases to the literature to advance our understanding of this disorder.  Systemic associations and risk of malignant transformation of PAON are also reviewed. Though PAON is relatively rare, this case also highlights that PAON should be added to the differential diagnosis of monodactylous erythronychia and onychodystrophy because the cutaneous lesions may be subtle as was true in this case.