Porokeratosis 2, Palmar, Plantar, And Disseminated Type

Description

Porokeratosis is a rare skin disorder characterized by one or more annular plaques with a surrounding raised horny border that spreads centrifugally. Variants of porokeratosis have been described that differ in morphologic shapes, distribution, and clinical course (Schamroth et al., 1997). However, as noted by Sybert (2010), families with expression of more than one variant of porokeratosis among members, and individuals expressing more than one variant, have been reported, suggesting that the distinctions among these variants may be artificial.

Porokeratosis palmaris plantaris et disseminata (PPPD) is a subtype in which lesions initially develop on the palms and soles, but later involve other parts of the body, including the trunk and limbs (Wei et al., 2003).

For a discussion of genetic heterogeneity of porokeratosis, see 174800.

Clinical Features

In 8 persons in 4 generations, Guss et al. (1971) described a form of porokeratosis distinct from both the Mibelli (175800) and disseminated superficial actinic (175900) types. The lesions appeared first on the palms and soles in the late teens or early twenties and subsequently on other parts of the body, including areas not exposed to ultraviolet radiation.

Wei et al. (2003) reported a 5-generation family from the Anhui province in China in which 18 individuals had PPPD. Affected family members had onset of lesions on the palms and soles in their early twenties, except for 1 family member with onset at age 10 years. Multiple annular lesions ranged from 0.3 to 1 cm in diameter, and eruptions gradually spread to involve the entire trunk and extremities. Skin biopsy performed on 1 patient showed a flattened segment of epidermis with overlying hyperkeratosis bounded on either side by subtle epidermal depressions with overlying cornoid lamellae. Inheritance was autosomal dominant.

Inheritance

The family with porokeratosis reported by Guss et al. (1971) showed a pedigree pattern consistent with either autosomal or X-linked dominant inheritance.

The transmission pattern of porokeratosis in the family reported by Wei et al. (2003) was consistent with autosomal dominant inheritance.

Mapping

By analysis of microsatellite markers on chromosome 12q in a large Chinese family with PPPD, Wei et al. (2003) identified a 6.9-cM candidate region for the disorder on chromosome 12q24.1-q24.2 between markers D12S1613 and D12S1341 (maximum 2-point lod score of 8.14 at D12S1335). Wei et al. (2003) noted that the PPPD locus showed about 0.6-cM overlap with the DSAP1 locus (175900).