Bloom syndrome (often abbreviated as BS in literature) is a rare autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability. BS is caused by mutations in the BLM gene which is a member of the RecQ DNA helicase family. Mutations in other members of this family, namely WRN and RECQL4, are associated with the clinical entities Werner syndrome and Rothmund–Thomson syndrome, respectively. More broadly, Bloom syndrome is a member of a class of clinical entities that are characterized by chromosomal instability, genomic instability, or both and by cancer predisposition. Cells from a person with Bloom syndrome exhibit a striking genomic instability that includes excessive crossovers between homologous chromosomes and sister chromatid exchanges (SCEs). The condition was discovered and first described by New York dermatologist Dr. David Bloom in 1954.Bloom syndrome has also appeared in the older literature as Bloom–Torre–Machacek syndrome. Presentation
The most prominent feature of Bloom syndrome is proportional small size. The small size is apparent in utero. At birth, neonates exhibit rostral to caudal lengths, head circumferences, and birth weights that are typically below the third percentile.The second most commonly noted feature is a rash on the face that develops early in life as a result of sun exposure. The facial rash appears most prominently on the cheeks, nose, and around the lips. It is described as erythematous, that is red and inflamed, and telangiectatic, that is characterized by dilated blood vessels at the skins surface.
Despite these reductions, several women with Bloom syndrome have had children, and there is a single report of a male with Bloom syndrome bearing children.Although some persons with Bloom syndrome can struggle in school with subjects that require abstract thought, there is no evidence that intellectual disability is more common in Bloom syndrome than in other people.The most serious and frequent complication of Bloom syndrome is cancer. In the 281 persons followed by the Bloom Syndrome Registry, 145 persons (51.6%) have been diagnosed with a malignant neoplasm, and there have been 227 malignancies. The types of cancer and the anatomic sites at which they develop resemble the cancers that affect persons in the general population. The age of diagnosis for these cancers is earlier than for the same cancer in normal persons. And many persons with Bloom syndrome have been diagnosed with multiple cancers. The average life span is approximately 27 years. The most common cause of death in Bloom syndrome is from cancer. Other complications of the disorder include chronic obstructive lung disease and type 2 diabetes.There are a variety of excellent sources for more detailed clinical information about Bloom syndrome.There is a closely related entity that is now referred to as Bloom-syndrome-like disorder (BSLD) which is caused by mutations in components of the same protein complex to which the BLM gene product belongs, including TOP3A, which encodes the type I topoisomerase, topoisomerase 3 alpha, RMI1, and RMI2.