Description

A variant of psoriasis that characteristically affects the skin of the palms and soles. It is chronic and inflammatory in nature, with hyperkeratotic, pustular, or mixed morphologies; a therapeutically challenging condition that can produce significant functional disability and is associated with substantial impairment in quality of life

Epidemiology

• Palmoplantar psoriasis
  • Age: no specific age range
  • Gender specificity is unclear. Men and women almost equally affected in two studies, whereas male predominance is suggested by another study. The disease may be more common among farmers, manual laborers, and housewives.
• Palmoplantar pustulosis (PPP) (possibly related condition)
  • Age: onset 20 to 60 years
  • Predominant sex: female > male (8:2)

Incidence
Incidence has not been determined.

Prevalence
Psoriasis affects 2–5% of the population, with the palmoplantar variant comprising 3–4% of all cases of psoriasis.

Etiology and Pathophysiology

Antigenic triggers activate dendritic cells and T cells; IL-20 is produced locally, which accelerates keratinocyte proliferation; IL-23 is released from lymph nodes, recruiting TH1 and TH17 to the lesions; T cells produce numerous cytokines, including tumor necrosis factor-α (TNF-α), IL-17, and IL-22, which stimulate keratinocytes to proliferate and produce proinflammatory antimicrobial peptides and cytokines; neutrophils are recruited to the epidermis and activate dermal fibroblasts.

Genetics

• Psoriasis associated with human leukocyte antigen (HLA) Cw6
• Psoriasis is related to the psoriasis-susceptibility (PSORS1) locus on chromosome 6p21, but relation of this gene to palmoplantar psoriasis remains unclear.
• No association between PPP and the PSORS1 locus found in one study
• Variations of the CARD14 gene and genes in the IL-19 subfamily on chromosome 1q31 to 1q32 may be linked to PPP and plaque psoriasis.

Risk Factors

• Smoking
• Irritants
• Friction
• Manual or repetitive trauma
• Koebner phenomenon
• Anti–TNF-α agents have been shown to paradoxically induce palmoplantar eruptions.
• PPP: linked to thyroid disease, smoking, and arthritis of the anterior thorax

Commonly Associated Conditions

• PPP
  • Possibly related to dermatosis characterized by small, sterile pustules
  • It remains controversial if PPP is a type of palmoplantar psoriasis or a distinct entity.
  • The International Society of Psoriasis Associations deemed PPP as an independent entity in 2007.
• Psoriasis vulgaris is present on other parts of the body in cases of palmoplantar psoriasis.