Because of his age at onset and the mildness of his symptoms, he was first suspected to have type III BS, but a new mutation (c.2762G > T p.Gly921Val, c.3233C > A p.Thr1078Lys) in the SLC12A1 gene, which is associated with type I BS, was detected by targeted sequencing and confirmed by Sanger sequencing. This evidence concerns the gene SLC12A1 and Bloom syndrome.