Eruption of a pus-filled kind

By Dr Adrian Lim

A 45-YEAR-OLD man presents with striking pus-filled blisters on the palms and soles (Figure 1). There is moderate discomfort and significant impairment to walking and using his hands.

The eruptions started a month ago as small pustules that rapidly coalesced into flaccid pus-filled blisters. He has no history of dermatitis or allergies and is experiencing this eruption for the first time. He is otherwise well, smokes a packet a day, and is not on any regular medications. What is the most likely diagnosis?

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Figure 2. Lesions start as small pustules.

Palmoplantar Pustulosis (PPP)

This is an uncommon symmetrical pustular eruption of the palms and soles that typically starts as small pustules (Figure 2) that can coalesce into larger pus-filled blisters. The exact cause is unknown and propositions include: immunological reaction to infection (e.g. tonsillitis) and sweat gland dysregulation in the palms and soles. It has also been proposed that the sweat gland dysfunction leading to blisters and pustules is triggered via nicotine receptors and hence the strong correlation with heavy smoking (>20/day).

The differential diagnosis for PPP includes vesicular dermatitis (Figure 3), pustular tinea and pustular psoriasis of the palms and soles. Controversially, PPP has been classified as a subtype of pustular psoriasis but others have disputed this. Pustular psoriasis is typically generalised rather than localised to palms and soles and usually accompanied by other features of psoriasis (e.g. nail and scalp changes). PPP patients have a greater incidence of autoimmune disorders and thyroid disease.

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Figure 3. Differentials include vesicular dermatitis.

Investigations

PPP is essentially a clinical diagnosis and does not require a biopsy. In the acute pustular phase, bacterial swabs are usually undertaken but will be sterile. Fungal scraping should be done if there is evidence of tinea, especially in chronic cases where there is hyperkeratosis and scaling. 

Managing PPP

PPP can be difficult to control. Milder cases may respond to potent topical steroids (e.g. Diprosone) under occlusion or wet dressings. However, systemic steroids should be avoided as they can lead to rebound and worsening of the condition. Wet dressings can be achieved by wearing damp cotton gloves and socks after application of topical steroids. The wet dressing is left on for several hours and can be applied overnight.

Burow’s solution (aluminium acetate) and Condy’s solution (potassium permanganate 1:8000), as soaks or compress, can help prevent maceration and dry out the blisters. Chronic cases become hyperkeratotic and may require keratolytics and tar. Chronic, refractory and relapsing cases may benefit from phototherapy or systemic retinoids (Neotigason, start at 10—20mg/day). Refractory or severe PPP can usually be controlled with Neotigason without recourse to immunosuppressives such as cyclosporine or methotrexate.

Patient progress and case discussion

Given the severity of the presentation, the patient was started on oral Neotigason (20mg daily). He was also prescribed potent topical steroids (Diprosone) wet dressings applied twice a day and overnight, as well as aluminium acetate soaks to dry out the exudate.

He was advised to commence a smoking cessation program and was transitioned to nicotine patches (a lesser trigger than cigarettes) in the interim.

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Figure 4a. The pustular lesions at presentation.

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Figure 4b. Two weeks after commencing treatment.

At the two-week review, the pustules had cleared up significantly (Figures 4a, 4b) and he was able to return to work. At review he had stopped smoking for two weeks and was motivated to quit for good. The ongoing management will centre on sustained smoking cessation, and managing any subsequent relapses, in partnership with the GP. Patients who continue to smoke tend to have refractory PPP even with optimum therapy. PPP may sometimes recur after a period of remission, and a minority will suffer a chronic relapsing course, usually with cigarette smoking as a trigger.

PPP key facts:

  • Aetiology unknown
  • Rapid onset with chronic and relapsing course
  • Sterile pustules
  • Historical link to pustular psoriasis
  • Chemical soaks may be helpful
  • Potent topical steroids under occlusion may help
  • Systemic steroids should be avoided
  • Severe cases may require systemic retinoids
  • Stop smoking!

This article first appeared in Medical Observer on the 31st of March, 2015

A 45-YEAR-OLD man presents with striking pus-filled blisters on the palms and soles (Figure 1). There is moderate discomfort and...

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