Keratosis Palmoplantaris Striata Ii


A number sign (#) is used with this entry because of evidence that keratosis palmoplantaris striata II (PPKS2) is caused by heterozygous mutation in the DSP gene (125647) on chromosome 6p24.


PPKS2 is characterized by linear hyperkeratosis of the palms, which is particularly evident in affected individuals who perform manual labor. Hyperkeratosis of the soles primarily involves pressure points, and diffuse background palmoplantar thickening may also be present. (Armstrong et al., 1999; Whittock et al., 1999).

For a discussion of genetic heterogeneity of the striate form of palmoplantar keratoderma, see PPKS1 (148700).

Clinical Features

Armstrong et al. (1999) studied a large family segregating autosomal dominant striate palmoplantar keratoderma. Affected individuals developed palmoplantar thickening in the first or early second decade of life. This was most prominent in a linear pattern along the flexor aspects of the fingers and over pressure points on the soles. There was a tendency to a coexistent milder, more diffuse background palmoplantar thickening in some. Individuals were prone to develop fissuring but there was no history of frank blister formation. There were no skin changes outside the palmoplantar areas, and no abnormalities of hair, nails, or teeth were noted.

Whittock et al. (1999) studied a 45-year-old male construction worker with a 20-year history of dry flaking skin on his palms and soles that gradually became thicker, exacerbated by heavy manual labor. Examination revealed hyperkeratosis with a marked linear appearance on his right palm, whereas the hyperkeratosis was more diffuse on his left palm and was more focal on the soles of his feet. The proband's mother had signs of focal plantar keratoderma, but her palms showed only mild skin dryness, and the proband's 8-year-old son showed some hyperkeratosis on the plantar aspect of the right great toe. The proband had 3 unaffected sibs and an unaffected 14-year-old daughter. Light microscopy of lesional palmar skin showed acanthosis and hyperkeratosis, with widening of keratinocyte intracellular spaces throughout the spinous layer. Ultrastructurally, desmosomes were smaller and fewer compared to site-matched control skin, and the attachment of the keratin filament network to the plasma membrane was perturbed. In addition, the keratin filaments were condensed and compacted in a perinuclear distribution.

Wan et al. (2004) analyzed skin biopsies from patients previously studied by Armstrong et al. (1999) and Whittock et al. (1999), with PPKS due to mutations in the DSP gene (see MOLECULAR GENETICS). Confocal microscopy showed extensive reduction of desmoplakin, desmocollins (see 125643), and plakophilin (see 601975). In addition, there were marked alterations in keratin expression and organization, including expression of the basal cell keratin pair K5 (148040)/K14 (148066) in suprabasal layers, and restriction of K1 (139350) to a perinuclear location. Patches of K10 (148080)-positive and -negative cells were admixed within the rete ridges. Wan et al. (2004) concluded that mutations in DSP causing PPKS2 may be associated with perturbations in epidermal differentiation accompanied by a marked disruption of several components of the epidermal scaffold, including desmosomes and the keratin intermediate filament (KIF) network.


In a large family segregating the striate form of palmoplantar keratoderma, Armstrong et al. (1999) excluded linkage to the 18q21 region where the PPKS1 locus had been mapped. By microsatellite typing with markers mapping to other regions, they demonstrated linkage of the disorder (PPKS2) to 6p21 with a maximum lod score of 10.67.

Molecular Genetics

In affected members of a large family with a striate form of palmoplantar keratoderma mapping to chromosome 6p21, Armstrong et al. (1999) identified heterozygosity for a nonsense mutation in the DSP gene (Q331X; 125647.0001). The authors stated that this was the first inherited skin disease in which haploinsufficiency of the structural element was implicated.

In a 45-year-old man with striate palmoplantar keratoderma, Whittock et al. (1999) sequenced the desmoplakin gene and identified heterozygosity for a splice site mutation (125647.0024) that was also found in his mildly affected mother and son as well as his 3 unaffected sibs. The authors concluded that trauma was clearly relevant to phenotypic expression in this family, since the clinical features were most prominent in the affected member who worked as a manual laborer, whereas his mother and sibs with sedentary jobs had mild or undetectable physical signs.