Palmoplantar pustulosis (PPP) is uncommon, affecting roughly 6 to 9 people per 100,000 in the United States. That makes it rare enough that many general practitioners won’t see it regularly, but common enough that dermatologists encounter it with some frequency. The condition causes recurring sterile pustules on the palms and soles that cycle through eruption, browning, and scaling.
How rare it is depends heavily on where you live, your sex, and even whether the condition gets correctly identified in the first place. More than half of patients are initially misdiagnosed, which means the true numbers are likely higher than what databases capture.
Prevalence by the Numbers
The best available estimates come from insurance claims and electronic health records across multiple countries. In 2020, the prevalence in the U.S. ranged from about 6 to 9 per 100,000 people depending on the database used. Sweden reported 20 to 26 per 100,000, and Denmark around 5 per 100,000. Germany’s estimates vary widely, from 80 per 100,000 in one analysis to lower figures in others.
Japan is a clear outlier. Nationwide claims data put the Japanese prevalence at roughly 89 to 120 per 100,000, making PPP about 10 to 15 times more common there than in the U.S. The reasons for this gap aren’t fully understood, but genetic background, diagnostic practices, and smoking rates all likely play a role. If you’re in the U.S. or most of Europe, PPP sits firmly in the “uncommon” category. In Japan, it’s closer to a condition most dermatologists see routinely.
Why Geography Makes Such a Difference
The tenfold gap between Japan and Western countries is one of the most striking features of PPP epidemiology. Part of it may be real biological variation. Japanese researchers have studied PPP extensively and have well-established diagnostic criteria, which means cases are less likely to be missed or lumped in with other conditions. In the U.S. and Europe, PPP is more frequently confused with hand eczema or other forms of psoriasis, so reported prevalence may undercount actual cases.
There’s also a classification question. Some countries treat PPP as a subtype of psoriasis, while others consider it a distinct disease. This affects how cases are coded in medical records and insurance claims, which in turn affects the numbers researchers pull from those databases.
Who Gets It
PPP is overwhelmingly a condition of middle-aged women. Women account for 58% to 94% of patients across studies worldwide, with most research finding a female-to-male ratio of at least 3.5 to 1. The typical age of onset falls between the 40s and 50s, and the highest prevalence occurs between ages 50 and 69. It’s rare in children and uncommon before age 30.
Smoking is the single strongest lifestyle risk factor. The association is so consistent across studies that PPP is sometimes described as a “smoker’s disease,” though it certainly occurs in nonsmokers too. If you have PPP and smoke, quitting doesn’t guarantee improvement, but it’s one of the few modifiable factors linked to the condition.
Often Mistaken for Eczema
One reason PPP may seem rarer than it actually is: it’s frequently misdiagnosed. A registry study from the British Journal of Dermatology found that 54% of PPP patients were initially told they had eczema. That initial misdiagnosis led to an average delay of nearly 3 years before they received the correct diagnosis. Some patients waited much longer.
The confusion is understandable. Both conditions can cause red, scaling, itchy skin on the hands. But PPP has a distinctive pattern: small, well-defined pustules that appear in crops on the palms or soles, turn brown as they dry, and then peel. The pustules are sterile, meaning they contain white blood cells but no bacteria. If you’ve been treated for hand eczema for years without improvement, PPP is worth asking your dermatologist about.
Connection to Psoriasis and Other Conditions
Whether PPP is a form of psoriasis or its own disease is still debated. Genetically, PPP looks quite different from the more common plaque psoriasis. Mutations in genes involved in skin inflammation, particularly one called IL36RN, are found in only about 3% of PPP patients, compared to 19% of people with generalized pustular psoriasis. The combined frequency of the most studied genetic mutations in PPP patients is less than 10%, suggesting that the genetic drivers are largely unknown or involve different pathways than other pustular skin diseases.
PPP does come with notable associations beyond the skin. A study comparing PPP patients to matched controls found thyroid disease in 53% of PPP patients versus 16% of controls. Enlarged thyroid glands and thyroid autoantibodies were both more common. This doesn’t mean PPP causes thyroid problems or vice versa, but it suggests shared immune system dysfunction. If you have PPP, thyroid screening is reasonable.
Some patients also develop bone and joint inflammation, particularly in the chest wall (a combination sometimes called SAPHO syndrome). Pain or swelling at the collarbone or breastbone in someone with palm or sole pustules is a recognizable pattern that points toward this overlap.
Putting the Rarity in Perspective
To put PPP’s prevalence in context: psoriasis affects roughly 2,000 to 3,000 per 100,000 people in Western countries. PPP, at 6 to 9 per 100,000 in the U.S., is roughly 300 times less common. It’s more prevalent than many orphan diseases but rare enough that finding a dermatologist experienced with it can take effort, and clinical trials for new treatments are smaller and fewer than for common skin conditions.
The practical consequence of this rarity is limited treatment options. Because PPP affects a small population and responds poorly to many standard psoriasis therapies, fewer drugs have been specifically tested or approved for it. Treatment often involves trial and error with topical therapies, light therapy, or systemic medications originally developed for other inflammatory conditions. The path to finding what works can be frustratingly long, compounded by the years many patients already spent under the wrong diagnosis.