Identification of somatic and germline mosaicism for a keratin 5 mutation in epidermolysis bullosa simplex in a family of which the proband was previously regarded as a sporadic case

The study identified somatic and germline mosaicism for a keratin 5 mutation in a family with epidermolysis bullosa simplex (EBS), initially thought to be a sporadic case. The proband had a heterozygous 1649delG mutation in the keratin 5 gene, not detected in the parents' blood samples. However, the same mutation was found in the proband's younger sister and in the mother's DNA from hair bulb and buccal cell samples, but not in her blood. This indicated maternal somatic and germline mosaicism, highlighted by the mother's childhood skin pigmentation. The findings underscored the importance of considering mosaicism in genetic counseling for EBS.