Systematized porokeratotic eccrine and hair follicle naevus: report of a case and review of the literature.

We report a unique case of a congenital keratinocytic naevus associated with severe alopecia, onychodysplasia and palmoplantar involvement in a 13-year-old girl. The lesions, consisting of scaly, spinous and verrucous papules and plaques, mainly followed Blaschko's lines and have remained unchanged since birth. The predominant histopathological picture was that of a column of parakeratosis overlying the eccrine ostia and hair follicles. This is the first case of a systematized keratinocytic naevus characterized by histopathology of eccrine and hair follicle porokeratosis and a widespread bilateral involvement. This may be a distinct entity to be included in the differential diagnosis of linear, hyperkeratotic dermatoses. We suggest its classification as systematized porokeratotic eccrine and hair follicle naevus.