Palmoplantar pustulosis types

Isolated palmoplantar pustulosis appears as sterile pustules confined to the palms and/or soles, without any signs of psoriasis elsewhere on the body. Individuals with this form of PPP experience repeated pustular outbreaks on a red, scaly base, often leading to pain and discomfort that interferes with daily activities. Many experts consider this the “pure” form of PPP, differentiating it from broader psoriasis subtypes.

In this type, pustules can form in clusters in specific areas or present in a more dispersed pattern across the entire palm and sole surfaces. Although this condition is limited to the palms and soles, the severity can vary from mild to debilitating. 

Palmoplantar pustular psoriasis refers to cases where pustular lesions appear on the palms and soles in individuals who have a known history of psoriasis or develop plaque psoriasis elsewhere on the body. This condition is linked to broader psoriatic disease, and clinicians often use the term PPPP to reflect this connection.

Whether PPPP is a separate category or a variation of pustular psoriasis remains debated. Some clinicians consider PPPP as part of the clinical spectrum of pustular psoriasis, while others reserve the term for pustular outbreaks that occur in individuals with established psoriasis. Regardless of classification, PPPP tends to involve pustules on the palms and soles in people who already exhibit other symptoms of psoriasis. 

Acrodermatitis continua of Hallopeau is a rarer variant where pustular lesions extend to the tips of the fingers and toes, often affecting the nails. This form of PPP may start on the palms or soles and slowly spread, causing nail dystrophy, subungual pustules, and sometimes changes to the bones in the fingertips or toes.

ACH shares features with classic PPP, such as sterile pustules and chronic recurrence, but it differs by involving the nails and distal digits. Researchers often consider ACH a part of localized pustular psoriasis due to the shared characteristics and immune response. 

In some cases, palmoplantar pustulosis appears as part of a broader syndrome that includes bone and joint involvement. One example is SAPHO syndrome, which includes synovitis, acne, pustulosis, hyperostosis, and osteitis. In this form, pustules on the palms and soles are accompanied by inflammatory bone and joint changes.

SAPHO syndrome is less common than isolated PPP but requires a multidisciplinary approach for management, as it involves dermatology and rheumatology specialists due to the joint and skeletal symptoms. 

Certain medicines, particularly biologic drugs used to treat autoimmune conditions, can trigger pustular eruptions on the palms and soles. This drug-induced form mirrors classic PPP but occurs as a reaction to specific therapies rather than the usual triggering factors of palmoplantar pustulosis.

Drug-induced PPP typically manifests after starting medicines such as tumour necrosis factor (TNF) inhibitors or other immune-modulating drugs. Recognizing this form of PPP is crucial, as discontinuing or switching the triggering drug often leads to symptom improvement.