Bloom syndrome is a rare genetic disorder characterized by growth retardation, sunlight sensitivity and a weaker immune system. Common symptoms include short stature, skin rashes upon sun exposure, high-pitched voice and distinct facial features (long and narrow face, prominent nose and ears, small jaw). People with Bloom syndrome have moderately compromised immune system, leading to recurrent infections such as pneumonia, ear infections and chronic lung disease. Male may have problems with infertility in females may have reduced fertility. Other complications of Bloom syndrome involve chronic obstructive pulmonary disease (COPD), diabetes, learning disabilities and predisposition to cancer. Bloom syndrome is caused by mutations in the BLM gene, which encodes a protein called RECQL3 (RECQ protein-Like 3). RECQL3 is responsible for repairing damage to DNA and maintaining the stability of DNA during DNA replication. There are more than 70 BLM gene mutations identified in the BLM gene. In most cases, the specific mutation that caused Bloom syndrome is 2281del6ins7, which involves deletion and insertion of nucleotides, leading to production of an abnormally short, non-functional RECQL3 protein. This in turn results in a high chromosome breakage and mutation rate in the BLM gene. Without this protein, DNA damage cannot be repaired effectively, and the cells can divide in an uncontrollable way, giving rise to the symptoms of Bloom syndrome and predisposition to cancer.     References: Arora H, Chacon AH, Choudhary S, McLeod MP, Meshkov L, Nouri K, Izakovic J (2014). Bloom syndrome. International Journal of Dermatology, 53: 798–802. Sanz MM, German J, Cunniff C. (2006)
[Updated 2016 Apr 7]. Bloom’s Syndrome. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Jose CP, Ferreira MD, Schreiber-Agus N, Carter SM, Klugman S, MDa, Gregg AR, Gross SJ (2014). Carrier testing for Ashkenazi Jewish disorders in the prenatal setting: navigating the genetic maze. American Journal of Obstetrics and Gynecology. 211(3): 197-204.