Nagoya University research identified a patient with the whole-body skin disease epidermolytic ichthyosis that had been inherited as a germline mutation from her father with the milder epidermolytic nevus. Analysis of genomic DNA from the patient revealed a mutation in the keratin 10 gene, which was identical to that observed in cells taken from patches of thickened skin on the father’s body. Assessing transmission risk of such diseases allows affected couples to receive genetic counseling.