Porokeratotic eccrine ostial and dermal duct nevus and a similar condition, porokeratotic eccrine and hair follicle nevus, are rare disorders of keratinization with eccrine and hair follicle involvement. We describe the clinical features in 5 patients, all of whom had widespread skin involvement following the lines of Blaschko. Two patients presented with erosions in the newborn period as the initial manifestation of their disease; one had an associated structural anomaly, unilateral breast hypoplasia; and one adult had malignant transformation in the nevus with development of multifocal squamous cell carcinomas. Three patients had histologic involvement of both acrosyringia and acrotrichia. Based on the observation of overlapping histologic features, we propose the name "porokeratotic adnexal ostial nevus" to incorporate the previously described entities porokeratotic eccrine ostial and dermal duct nevus and porokeratotic eccrine and hair follicle nevus.