Palmoplantar Pustulosis (PPP)

What palmoplantar pustulosis is

PPP is driven by the immune system. Immune signals, particularly from the interleukin-36 and interleukin-17 pathways, attract white blood cells (neutrophils) into the skin around sweat ducts, where they collect as tiny pustules. Because these collections contain white cells but no bacteria or fungus, they are described as sterile.

Doctors have long debated whether PPP is a form of psoriasis. About 10 to 25% of people with PPP also have typical plaque psoriasis elsewhere, and PPP is often called palmoplantar pustular psoriasis. However, its genetics and triggers differ, and European dermatology guidelines now classify it as a separate condition.

Symptoms

• Pustules: yellow or white spots 2 to 5 mm across, appearing in crops on the palms, especially the base of the thumb, and the soles, especially the heels and insteps
• Color change: pustules dry and turn brown over about 1 to 2 weeks, so new yellow and old brown spots are seen together
• Red, thickened, scaly skin underneath
• Cracked skin and fissures that can be very painful
• Itching or burning, often before a new crop appears
• Nail changes in some people, such as pitting, ridges or thickening

It usually affects both hands, both feet or all four, and comes and goes in flares over years. Pain from cracks can make walking and manual work difficult, and PPP has a large effect on quality of life.

Causes and triggers

The exact cause is unknown, but these factors are strongly linked:

• Smoking: around 80 to 95% of people with PPP smoke or used to smoke. Nicotine may affect receptors in the sweat ducts. Stopping smoking can improve PPP, though it often takes months.
• Sex and age: women aged 40 to 60 are affected most.
• Other autoimmune conditions: thyroid disease, celiac disease and type 1 diabetes are more common in people with PPP.
• Infections: chronic tonsil, dental or sinus infections may trigger flares in some people.
• Stress, friction and irritants on the hands and feet.
• Medicines: TNF-inhibitor biologics occasionally trigger a PPP-like rash.

A rare linked condition, SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis), combines pustules with bone and joint inflammation, typically in the front of the chest wall.

PPP vs similar conditions

Diagnosis

A dermatologist usually diagnoses PPP by its appearance. Tests may include:

• skin scrapings to rule out a fungal infection
• a swab of a pustule to show there are no bacteria, or to detect infection in cracks
• patch testing if contact allergy is suspected
• blood tests for thyroid function, celiac disease and blood sugar, in some people
• a skin biopsy occasionally, when the diagnosis is unclear

Treatment

PPP is notoriously stubborn. The aim is to reduce flares and pain, and treatment usually needs to be continued for months.

First-line treatment

• Stop smoking. This is the single most important lifestyle step.
• Very potent topical steroids, such as clobetasol, used once or twice daily. Covering them with plastic wrap or cotton gloves overnight (occlusion) improves absorption into the thick palm and sole skin. Use in courses as directed to avoid skin thinning.
• Emollients and urea or salicylic acid creams to soften scale and prevent cracks.
• Protecting the skin: cotton-lined gloves for wet work, comfortable footwear and cushioned insoles.

Second-line treatment

• Phototherapy: targeted UV light treatment of the hands and feet, especially PUVA (psoralen plus UVA), 2 to 3 times a week for several weeks.
• Acitretin: a vitamin A-related tablet that is often effective. It causes severe birth defects, so it is not used in people who could become pregnant during treatment or for 3 years afterward.
• Methotrexate or cyclosporine tablets for severe disease, with regular blood tests.

Newer options

Biologic injections that target IL-23 or IL-17 and the tablet apremilast have shown benefit in trials. Some are approved for PPP in certain countries; elsewhere they may be used off-label, especially when psoriasis is also present.

Outlook

PPP is long-lasting, often running for years with flares and quieter periods. In some people it fades on its own after several years. Stopping smoking, consistent skin care and finding the right treatment combination control it well for many people, though few treatments clear it completely.

Frequently asked questions

What causes palmoplantar pustulosis?

The cause is not fully understood. It is an immune-driven inflammation in the skin of the palms and soles. Smoking is the strongest known trigger, and most people with PPP smoke or have smoked. Genetics, other autoimmune diseases, infections, stress and friction can also play a part.

Is palmoplantar pustulosis contagious?

No. The pustules are sterile, meaning they contain white blood cells but no bacteria, viruses or fungi. You cannot catch PPP from touching someone or sharing towels. Cracked skin can occasionally become infected, which needs separate treatment.

Is palmoplantar pustulosis a type of psoriasis?

It is closely related. Some people with PPP also have plaque psoriasis, and it is often called palmoplantar pustular psoriasis. Research shows differences in genetics, triggers and treatment response, so many dermatologists now consider it a separate but overlapping condition.

Will stopping smoking clear palmoplantar pustulosis?

Stopping smoking often helps reduce flares and makes treatments work better, but improvement can take months and does not always clear the condition. It is still strongly recommended, because continued smoking is linked to more persistent and severe disease.

What is the best cream for palmoplantar pustulosis?

A very potent steroid cream or ointment, such as clobetasol propionate, is usually the most effective first treatment, often under occlusion overnight. Thick emollients and urea creams help with cracking. A dermatologist will prescribe and supervise strong steroid use to limit side effects.