Palmoplantar psoriasis, a frequent and severe clinical type of psoriasis in children

Editor Psoriasis affects 0.5–0.7% of European children and in 25–40% of cases, the disease starts in childhood. Some clinical features seem specific to children: face involvement, guttate and inverse psoriasis are more common, plaques are often smaller and the scale thinner than in adults, diaper rash is quite specific. On the other hand, rheumatism and erythroderma are considered rare. Palmoplantar psoriasis affects 10–20% of adults and can be considered severe since it is socially detrimental and difficult to treat. Three main clinical types are observed: palmoplantar plaque psoriasis (PPPP), palmoplantar pustulosis (PPPu) and acrodermatitis (AD). The aim of this study was to study the frequency, clinical and epidemiological aspects of palmoplantar psoriasis in children. v-Psocar was a case–control, multicentre study performed to evaluate frequency of overweight in children with psoriasis. Description of the cohort and the first results has been published. Herein we evaluated the 312 children (0–18 years) included in v-Psocar. Palmoplantar psoriasis was classified as PPPP, PPPu and AD. Severe psoriasis was defined as psoriasis requiring phototherapy, or systemic treatment. Definition of comorbidities has been previously reported. Sixty-three (20.2%) children had palmoplantar psoriasis. It was found in 3 infants (8.6%), 51 children (22.9%, P = 0.05 comparing to infants) and 9 adolescents (16.7%). Clinical data are detailed in Table 1. The clinical aspects were PPPP (Fig. 1) in 50 cases, PPPu in 8 cases and AD in 25 cases. In 45 cases (33 PPPP, 2 PPPu, 10 AD), the aspect was isolated, and in 38 cases two aspects were observed in the same patients. For 29 children, palmoplantar (21 PPPP, 1 PPPu, 7 AD) psoriasis was considered as the main aspect of the psoriasis. Palmoplantar psoriasis was associated with inverse (P = 0.0008) and nail (P < 0.0001) psoriasis, and severity (P = 0.001), but less frequently associated with guttate psoriasis (P = 0.002). In this cross-sectional study, we showed that palmoplantar psoriasis is a frequent form of psoriasis. The main aspect is plaque type. It is statistically associated with inverse psoriasis and nail involvement. Acute psoriasis – i.e. guttate psoriasis – was not associated with palmoplantar involvement. For nearly 50% of children, phototherapy of systemic treatment (definition of the severity) was required. Palmoplantar involvement prevalence in children ranges from 1.6% to 18.5% in the literature. We show a higher prevalence. Three explanations can be proposed: (i) our methodology leads to an exhaustive evaluation; (ii) we had hospital recruitment, selecting more severe forms of psoriasis; (iii) Finally, lower frequencies reported in the literature might be explained by the author’s tendency to separate the AD from the other palmoplantar psoriasis forms. We think that it has to be included in the palmoplantar forms since the association between AD and other palmoplantar aspects is frequent as shown in our study. The role of occupational trauma has been discussed to explain the palmoplantar involvement. This ‘Koebner bias’ does not explain the high frequency of palmoplantar psoriasis found in our study. We did not detect any association between sport practice, or gender, and palmoplantar involvement that could increase the frequency of this type of psoriasis. Literature data on the association between palmoplantar psoriasis and nail involvement are discordant. Brunasso reported a lower frequency of nail involvement in adult patients affected by PPPP. Furthermore, another study did not demonstrate any association between nail changes in childhood psoriasis and the type of psoriasis. The association between inverse psoriasis type and palmoplantar involvement seems to be unrecognized. We have no explanation for this association. On the other hand, the lower frequency of guttate psoriasis in case of palmoplantar involvement has not been reported yet. It can be explained by the acute aspect of guttate psoriasis, while palmoplantar involvement is a chronic psoriasis. Finally, we found that palmoplantar psoriasis was related to disease severity, defined by the use of phototherapy of systemic treatment. This is corroborated by a case–control study showing a significantly greater physical disability and physical discomfort in patients with palmoplantar involvement than patients without palmoplantar involvement. The authors thank Dr S. Barbarot (Nantes), Dr D. Bessis (Montpellier), Dr O. Boccara (Paris), Pr C. Bodemer (Paris), Dr E. Bourrat (Paris), Dr C. Eschard (Reims), Dr M.Ferneiny (Paris), Dr C. Fleuret (Quimper), Dr T. Hubiche (Fr ejus), Dr I. Kupfer (Quimper), Dr C. L eaut e-Labr eze (Bordeaux), Pr J.-P. Lacour (Nice), Dr J. Miquel (Rennes), Dr E. Puzenat (Besanc on), Dr A.-L. Souillet (Lyon) and Pr P. Vabres (Dijon).