[Aquagenic palmoplantar keratoderma in children with cystic fibrosis]

Aquagenic palmoplantar keratoderma (APK) is a cutaneous phenomenon marked by the formation of edematous, translucent papules and plaques on the palms after water immersion. It can be observed in healthy subjects, but while this dermatosis is little known by practitioners treating these patients, most cases of APK have been described in patients with cystic fibrosis (CF). The primary objective of this study was to evaluate the frequency of APK in a population of children with CF. In addition, the relationship between APK and sex, genotype, pancreatic and pulmonary function, body mass index, and sweat chloride levels was analyzed.

This study was conducted in 60 children, 27 girls and 33 boys, aged 4 months to 18 years, followed at the CF care center at Angers (France) University Hospital, in whom CF had been confirmed by a positive sweat chloride level greater than 60 mmol. APK was determined by questioning searching for modifications of the palms noticed by the patient or his/her family after immersion in water and a clinical examination searching for the same signs before and after immersion of the right hand in a bucket of lukewarm water for 3 minutes (bucket sign).

Forty-seven out of 60 children (78%) had a positive bucket sign. Thirty-eight upon these 47 children had already noticed modifications of the skin on their palms, appearing quickly during the bath and 6 had an edema and an increase in skin folds on the palms of the hands even before immersion of their hand in water. No genotype-phenotype correlations were detected in patients with APK, nor were there associations of APK with other phenotypic features of CF.

APK is very frequent in patients with CF. It is most probably a consequence of the dysfunction of the CFTR protein. It should be systematically sought in all patients with CF. Its discovery in another context should suggest the diagnosis of CF or a carriage to the heterozygous state of a mutation involved in the disease.