In this issue… PPP: What's New in the Treatment, Pathogenesis and Terminology?
Wozel & Vitéz (1) report in a letter the clearance of palmoplantar pustular psoriasis (PPP) during treatment with efalizumab. Other case reports have indicated promising results with efalizumab, but there have been no controlled studies. On the other hand, there are reports of worsening or precipitation of the disease by tumour necrosis factor (TNF)-alpha blockers, which are so useful in the treatment of generalized pustular and plaque types of psoriasis. Incidentally, this raises a concern about what name should be used for this disease. At present there is confusion on this issue. In Rook's Textbook it is considered to be a localized form of pustular psoriasis, but they use the name palmoplantar pustulosis and provide several synonyms, among them pustulosis palmaris et plantaris. Others use the term palmoplantar psoriasis with or without a hyphen. Does this matter? Yes certainly! If there is no consistency in the terminology then reliable information about the disease cannot be obtained. I checked PubMed for the titles palmoplantar pustulosis/palmo-plantar pustulosis/palmoplantar psoriasis/palmo-plantar psoriasis with a highly variable and unreliable result. For example, none of our 12 published articles 1998–2007 on PPP appeared.
PPP is a complex and probably distinct disease without association with the candidate genes within the PSORS1 locus (2). Ninety percent of people with PPP are women and 95% are smokers at the start of their PPP. The target for the inflammation is the palmoplantar sweat duct; inflammation is intense, with large numbers of lymphocytes and mast cells in the papillary dermis, and with neutrophils and eosinophils migrating outwards in the sweat duct. PPP patients have an increased prevalence of autoimmune thyroid disease, abnormal calcium homeostasis, gluten sensitivity and diabetes type 2. As many as 30% of patients have long periods of sick leave/sickness pension. PPP is difficult to treat. Cessation of smoking is important, and this is often followed by a milder disease course. Gluten sensitivity should be checked and, if present, dietary treatment may induce the clearance of, or a remarkable improvement in, PPP. Controlled studies with efalizumab or possibly other biologicals with non-TNF blocking properties are required and, it is hoped, will be of value for those with treatment-resistant PPP. However, we need to be able to find the information: the question is which name should be used? Why not palmoplantar pustulosis?
1. Wozel G, Vitez L Palmoplantar pustular psoriasis: successful therapy with efalizumab after non-response to infliximab. Acta Derm Venereol 2007; 87: 00–00.
2. Asumalahti K, Ameen M, Suomela S, Hagforsen E, Michaëlsson G, Evans J, et al. Genetic analysis of PSORS1 distinguishes guttate psoriasis and palmoplantar pustulosis. J Invest Dermatol 2003; 120: 627–632.