The First Report on BLM Gene Mutations in Iranian Patients with Different Phenotypes of Bloom Syndrome: Identifying Two Mutations and a Literature Review on BLM Gene Mutations

Bloom syndrome (BS), also called congenital telangiectatic erythema, is a rare autosomal recessive inherited disorder characterized by genomic instability and predisposition to the development of all types of cancer. Besides, additional presentations have been observed in BS. Herein, we investigated the clinical and genetic aspects ofeight patients withBS in three unrelated Iranian families that exhibit less common symptoms like intellectual disability and polydactyly. After the thorough clinical examinations, whole-exome sequencing (WES) was performed. Following the detection of candidate variants, the familialco-segregation analysis was carried out by PCR-based Sanger sequencing. Meanwhile, a literature review was carried out by utilizing databases to compile information on BLM gene mutations from 2007 to the present. We identified two pathogenic nonsense mutations in the BLM gene in the studied families with the homozygous state. The first one, c.3415C>T (p.Arg1139Ter) mutation, was detected in the 5 patients from family 1 and one patient from family 3. The second one was c.2695C>T (p.Arg899Ter) mutation identified in the two patients from family 2. All unaffected parents were identified with the heterozygous state for the detected mutations in their affected offspring. Through our research in various articles, we gathered twelve different mutations in 17 BS patients from 2007 to the present. Mutation identification and presenting clinical manifestation of the rare disorder make it much easier and faster to diagnose this syndrome from other similar disorders. It also helps with carrier detection, as well as, prenatal diagnosis of bloom syndrome in high-risk families.