Cutaneous mosaicism, in KRT1 pI479T patient, caused by the somatic loss of the wild-type allele, leads to the increase in local severity of the disease.

Background: Epidermolytic ichthyosis (BCIE, OMIM 113800), is an autosomal dominant disorder of the skin caused by mutations in keratin genes KRT1 and KRT10. We present two sporadic patients showing a mild diffuse ichthyosis with palmoplantar keratoderma. Interestingly, one of them shows a significant hyperkeratosis of palms and soles similar to those present in the Meleda disease (OMIM 248300).

Objective: In this paper we would clarify the genetic difference between the two patients, giving rise to the different phenotype.

Methods: Clinical evaluation, followed by histological and molecular analysis has been established for these patients.

Results: We demonstrated the presence of a genetic cutaneous mosaicism. Both patients carry the KRT1 pI479T substitution, but in the palmoplantar areas of one of them, only the mutated allele is expressed (hemizygous). This leads to highlight a new type of cutaneous mosaic, the palmoplantar mosaicism.