A transient epidermolysis bullosa simplex-like phenotype associated with bexarotene treatment in a G138E KRT5 heterozygote.

[epidermolysis bullosa simplex]

Basal keratinocyte lysis is the hallmark histopathological finding of epidermolysis bullosa simplex (EBS ), a group of rare heritable mechanobullous disorders characterized by intraepidermal blister formation and skin fragility . Over 100 mutations , found predominantly in the genes encoding keratins 5 and 14 (KRT 5 , KRT 14 ), have been described to account for a variety of clinical subtypes . EBS with mottled pigmentation (EBS-MP ) is a rare variant featuring childhood-onset reticulate hyperpigmentation and focal palmoplantar keratoderma , typically associated with a P 25 L KRT 5 mutation . In this report , we present the case of a 77 -year -old woman with a history of palmoplantar keratoderma who developed a transient EBS-MP -like phenotype associated with bexarotene treatment for cutaneous T-cell lymphoma . Genetic sequencing revealed a heterozygous G 138 E KRT 5 variant , present in approximately 10 % of the European population and only rarely associated with pathology . Bexarotene , which has been reported to alter keratin synthesis , caused vesiculobullous reactions with similar frequency in clinical trials . We propose that the cumulative effect of drug treatment and underlying G 138 E polymorphism resulted in transient basal keratinocyte lysis in our patient and provides a plausible explanation for this unusual bexarotene side effect .