LAUSR

A 12-day-old boy presented with cutaneous anomalies that had been present since birth. He was the first child of unrelated white parents, and had been born at gestational week 37 after an uneventful delivery. Physical examination revealed a subtle shiny membrane over the child’s entire body, with superficial areas of fissuring on the wrists, ankles, armpits and abdominal folds (Fig. 1a,b). The hair, palms and soles were normal. The mother had no medical conditions, while the father had been diagnosed with atopic dermatitis and palmoplantar keratoderma (PPK); PPK was also present in the child’s paternal aunt and grandmother. Physical examination of the father disclosed a generalized fine whitish desquamation without underlying erythema, and a diffuse well-demarcated symmetrical PPK with honeycomb appearance, which extended to the wrists and lateral aspects of the foot. There were no digital constrictions or knuckle pads (Fig. 2). Following informed consent, peripheral blood was drawn from the father for genetic testing. DNA sequencing identified a heterozygous pathogenic variant, 730insG, in the LOR gene. The child was diagnosed with loricrin keratoderma (LK), and daily emollients were recommended. At the 1-year follow-up, he was found to have developed a diffuse honeycomb-like PPK, while the rest of the skin appeared normal (Fig. 1c,d). LK (OMIM 604117), is a rare type of nonsyndromic ichthyosis caused by heterozygous variants in LOR, a gene belonging to the epidermal differentiation complex. Loricrin is the main component of the cornified cell envelope, constituting 70% of its mass. Mice deficient in loricrin have a congenital erythroderma with shiny and translucent skin, but this phenotype