Hyperkeratosis of the urinary bladder

Hyperkeratosis is rare in urologic disciplines and is then usually confined to the external genitalia. Hyperkeratotic changes within the vesicular sys tem, which is normally lined with urothelium, have not been previously desc ribed in the world literature. The only connection is found in the frequent combination of palmoplantar skin hyperkeratosis and common cancer of the u rinary bladder. Localized microscopic keratinization in leucoplakia has bee n described. Macroscopically visible hyperkeratosis within the urinary blad der has not been described. We would like to introduce a 36-year-old female with this hyperkeratosis of the bladder. Hyperkeratosis is constituted by a disruption in keratinization and a thick ening of the horny layer of the epidermis. A distinction is made between pr oliferative hyperkeratosis (often the result of hornification or keratiniza tion) and retention hyperkeratosis (brought about by reduced desquamation). Hyperkeratosis of the skin can be evoked by exposure to various chemical s ubstances. In addition to transitional epithelium, squamous epithelium is also found o ccasionally within the urinary bladder. Squamous cell carcinoma can result from this in up to 3% of patients with all types of carcinoma of the bladde r. Theoretically, therefore, is possible - although unlikely - for all othe r changes which are observed in squamous epithelium to appear within the ur inary bladder as well. A conceivable pathogenetic mechanism in the development of intravesical hyp erkeratosis would be a change in the urinary bladder, e.g. squamous epithel ial metaplasia (rarely accompanied by intravesical squamous cell carcinoma) . Keratinization is to be expected as a further rare event during this form ation of squamous epithelium, with subsequent keratinization. Hyperkeratosi s, which is otherwise found only in the area of the epidermis, must be rega rded as one such change of the squamous epithelium. The hyperkeratosis in t he case reported here was comparable to hyperkeratosis of the palms and sol es, since there were no pathohistologic signs of precancerous conditions li ke leucoplakia, Bowen's disease, senile keratosis, arsenic keratosis or pit ch warts. The basic pathophysiologic model has a certain probability, but has not bee n confirmed. In summary, the present case was a form of hyperkeratosis of t he urinary bladder that has not: been previously described In the world lit erature. In addition, there were no manifestations whatever anywhere on the surface of the body.