Psoriasis - Palmar Pustular

Synonyms: palmoplantar pustolosis (PPP), localised pustular psoriasis

A chronic inflammatory skin condition characterised by crops of sterile pustules occuring on one or both hands and/or feet. Eruptions of pustules occur unpredictably but repeatedly over years and affected areas become red, scaly and frequently painful.

Relationship to other forms of psoriasis is controversial: histologically has a psoriasform pathology but rare to have PPP in association with other types of psoriatic lesions.

Psoriasis is a relatively common condition, with a UK prevelance of 1.5% general population.¹ PPP is thought to affect less than 5% of those with psoriasis.

• More common in smokers² - indeed 95% are smokers at the onset of disease.³
• Familial clustering
• Onset usually in adulthood
• Recent case reports of new onset of PPP following infliximab therapy.⁴

Unknown, thought to be a combination of genetic and environmental factors. One theory contends that the condition is auto-immune triggered by smoking.³

• Multiple pustules occur within a well demarcated erythematous scaly plaque on the palms or soles.
• Colour sequence as pustules mature: start white, become yellow and then brown

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Acrodermatitis continua of Hallopeau (ACH): a rare indolent form of psoriasis with sterile pustular changes and dactylitis affecting the distal digits and nails.⁵

• Infected eczema - less defined, white vesicles rather than pustules, swabs often grow staph. Acute pompholyx is an episodic form of eczema affecting the palms and soles with bulla formation, frequently becomes infected.
• Tinea pedis - commonly unilateral or asymmetrical erythema, scaling and pustules. Toe clefts and nails usually involved.
• Reiter's disease - gross palmar and plantar lesions may occur (keratoderma blennorhhagica) which are histologically indistinguishable from psoriasis. Also affects the mouth and penis.

Evidence-based treatment for PPP is contentious. Various treatments are used but none is generally accepted as universally effective. A recent Cochrane Review highlighted methodological problems with the studies designed to differentiate between the efficacy of different approaches.⁸Within primary care:

• Encourage general measures:
  • Good footwear made from natural fibres
  • Avoidance of even minor trauma
  • Waterproof dressings over fissured areas
  • Rest affected area where possible
• Emollients are important:
  • Apply thick greasy emollients to soften skin and prevent fissures
  • Soak in warm water with emulsifying ointment
  • Use salicylic acid ointment or urea cream to peel dead skin
  • Wash with soap substitutes
• Potent topical steroid ointments eg clobetasone proprionate may be used twice daily for limited periods. High potency steroids are required in order to penetrate the thick skin of the hands and feet. Occlusion with clingfilm or dressings can enhance penetration but should not be used for more than 5 days in a row.
• Coal tar is messy but can be applied directly, often mixed into an ointment base.
• Calcipotriol can be helpful, apply twice a day and do not cover.

Primarily for help with diagnosis and treatment. Palms and soles are difficult sites to treat and palmar pustular psoriasis can be resistant to treatment so specialist advice may be required. Further treatment options dermatologists can use include:

• PUVA
• Acitretin (systemic retinoid)
• Tetracycline antibiotics
• Methotrexate
• Biologics eg etanercept for ACH.¹⁰

• Pain from lesions and associated fissuring may be significant.
• Walking and standing for long periods can exacerbate lesions on soles of feet.
• Manual activity can be uncomfortable if hands affected.
• Occupational and functional disability secondary to above.
• Depression more common in those with psoriasis, especially where condition resistant to treatment.

The condition tends to be chronic and poorly responsive to treatment. Exacerbations may be related to recurrence.¹¹