Background Aquagenic keratoderma is an uncommon condition that occurs after brief water exposure. An association with cystic fibrosis has been suggested. Histopathology is considered to be nonspecific. Objectives To describe the microscopic findings in seven of 12 new patients and compare the histopathological results of the lesions which appeared on the palmar skin after immersion into water with normal skin. Patients and methods Nine female and three male patients (mean age 27 years) were collected prospectively and evaluated for common demographic, clinical and histopathological features. Results Lesions were located on only the palms in seven patients; the soles were involved in two patients; and one patient had involvement of the dorsal aspect of the hands. One patient had a similar family history. None of the patients reported associated conditions. Genetic studies revealed heterozygosis for mutation in the cystic fibrosis gene in two patients. The most specific histopathological findings were: orthohyperkeratosis with increased thickness and abnormal staining of the stratum corneum; dilated acrosyringia and dermal eccrine ducts with hyperplasia of eccrine glands, clear cell change and vacuolation; increased capillaries around and adjacent to the eccrine glands. A skin biopsy taken after restoration of normal skin with drying revealed a normal stratum corneum with a physiological uniform stain and normal thickness without further evidence of dilation of acrosyringia or dermal eccrine ducts. Incipient dilation of the secretory and ductal structures was also observed in a transitional area between the involved and the clinically normal skin of the palms. Conclusions Aquagenic keratoderma may be associated with a heterozygous mutation in the cystic fibrosis gene. Although the diagnosis is a clinical one, histopathology is useful and may reveal some characteristic diagnostic clues. Aquagenic pseudokeratoderma seems to be a more appropriate term to name it.
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