Palmoplantar pustulosis

What is palmoplantar pustulosis?

Palmoplantar pustulosis is a benign, chronic, and often relapsing sterile pustular dermatosis affecting the palms and soles. It may occur in patients with psoriasis, however it likely represents a distinct clinical entity. It responds less reliably to biologic treatments effective in psoriasis.

A variant of palmoplantar pustulosis affecting the tips of the digits is called acrodermatitis continua of Hallopeau or acropustulosis.

What causes palmoplantar pustulosis?

The exact cause of palmoplantar pustulosis remains unknown. However, environmental factors such as smoking, manual or repetitive trauma, irritants, and friction have been associated with this condition. Aside from these factors, several theories have also been proposed:

• It may be a disorder of the eccrine sweat glands, which are most numerous on the palms and soles
• Increased numbers of Langerhans cells around sweat ducts in this condition suggest a possible antigen-driven process
• Genetic mutations involving IL36RN, CARD14, ATG16L1 and AP1S3 may be associated
• It is not associated with the major psoriasis susceptibility locus PSORS1 or HLA-C:09:02, suggesting a genetically distinct entity from plaque psoriasis.

Specific chemotactic factors may also contribute or propagate inflammation including increased expression of IL8 and IL17. Increased detection of tumour necrosis factor-alpha (TNF-alpha) and IL-17. IL-22 and interferon-gamma have also been detected. Complement pathway activation has also been noted.

Pustules and rusty dots in a scaly plaque typical of PPP 

Pustules on the palm due to PPP 

Typical lesions of PPP on the soles - redness, scale, pustules, and rusty red dots 

Florid pustules on the feet due to PPP 

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Who gets palmoplantar pustulosis?

Palmoplantar pustulosis commonly presents between the ages of 20 and 60 years, with a predilection for females (female-to-male ratio 4:1).

The majority of patients with palmoplantar pustulosis are cigarette smokers, with 70-90% of patients being current or former smokers. Smoking is also a disease-aggravating factor. It is thought that activated nicotine receptors in the sweat glands stimulate an inflammatory process.

Several associated conditions have been determined:

• Many patients have a concomitant diagnosis of psoriasis vulgaris and/or psoriatic arthritis
• One large population-based study utilising Swedish longitudinal register data found that patients with type 2 diabetes mellitus and/or COPD, as well as a generally higher comorbidity burden, are more likely to have palmoplantar pustulosis
• Other conditions that may be associated include hypertension, hyperlipidaemia, atopic dermatitis, thyroid disease, coeliac disease, metabolic disease, and depression.

Other described causes include:

• Drug-induced, particularly TNF-alpha inhibitors.
• Focal infections
• Metal allergies
• Stress.

What are the clinical features of palmoplantar pustulosis?

Palmoplantar pustulosis usually presents as crops of sterile pustules localised to the palms and soles. These pustules are 1-10mm in size, often admixed with yellow-brown macules and/or scaly, erythematous plaques. Lichenification and desquamation are also commonly seen.

Pustules are more commonly noted on the thenar and hypothenar eminences and central palm. As well as the instep, medial and lateral borders of the foot and the sides or back of the heel.

Patients complain of varying levels of pruritus, however a more common complaint is of a ‘burning’ sensation. Lesions may also develop into painful fissures, and psoriatic nail changes may be present.

Palmoplantar pustulosis varies in severity and is often chronic, due to its difficult-to-treat nature. Slow spread or extension may occur.

Palmoplantar pustulosis 

Palmoplantar pustulosis 

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What are the complications of palmoplantar pustulosis?

• Psychosocial impact
• Fissures
• Secondary infection

How is palmoplantar pustulosis diagnosed?

Palmoplantar pustulosis is generally a clinical diagnosis. Investigations may be helpful for ruling out differential diagnoses or excluding possible complications. This includes:

• Potassium hydroxide preparation (rule out cutaneous fungal infection)
• Skin scrapings for mycology culture
• Bacterial and viral swabs
• Punch biopsy (atypical presentation or refractory disease)
• Patch testing for possible associated metal allergies.

What is the differential diagnosis for palmoplantar pustulosis?

• Pompholyx
• Vesicular/bullous tinea (manuum and pedis)
• Contact dermatitis (irritant or allergic)
• Acrodermatitis continua of Hallopeau
• Bullous pemphigoid
• Palmoplantar plaque psoriasis
• Acute palmoplantar eczema
• Pustular bacterid of Andrews
• Scabies

What is the treatment for palmoplantar pustulosis?

Management of palmoplantar pustulosis is often difficult and the condition may be refractory to treatment. Options are discussed below.

General measures

• Smoking cessation
• Treatment of underlying infections including dental infections or tonsillitis
• Washing using a gentle, soap-free substitute
• Regular use of emollients and/or keratolytics to help soften dry skin and prevent fissures
• Comfortable footwear
• Socks that wick sweat (eg, bamboo, superfine merino wool), changing shoes, open shoes
• Staying cool

Specific measures

• Topical steroids (first-line pharmacological management)
  • Potent forms in ointment vehicles are most suitable and applied under occlusion for increased penetration (short-term only).
  • Occlusion involves covering the applied topical steroid with a plastic film (such as cling film, plastic bags, or polyethylene gloves) for a few hours or even overnight.
• Systemic treatment
  • Retinoids (eg, acitretin)
  • Methotrexate
  • Ciclosporin
• Phototherapy: PUVA, excimer lamp and photodynamic therapy
• Apremilast (phosphodiesterase-4 inhibitor)
• Biologics (variable effect)
  • Ustekinumab (IL-12/23 inhibitor)
  • Secukinumab (IL-17 inhibitor)
  • Guselkumab (IL 23 inhibitor)

What is the outcome for palmoplantar pustulosis?

The disease course of palmoplantar pustulosis is usually prolonged, unpredictable, and can be refractory to treatment. Even if remission is achieved, relapse is common.