Identification of Somatic and Germline Mosaicism for a Keratin 5 Mutation in Epidermolysis Bullosa Simplex in a Family Initially Regarded as a Sporadic Case

The study investigated a family affected by epidermolysis bullosa simplex (EBS), a blistering skin disease caused by mutations in keratin 5 or 14. Initially, the proband was considered a sporadic case due to a 1649delG mutation in the keratin 5 gene not found in the parents' blood DNA. However, the same mutation was later identified 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, as the mother had a history of skin pigmentation issues. The findings highlighted the importance of considering mosaicism in genetic counseling for EBS.