Definition
Bloom syndrome (OMIM #210900) is a rare hereditary disease associated with increased chromosome breakage. The number of spontaneous mutations is elevated, thereby explaining the increased cancer risk. The most distinctive symptom is significant growth restriction.
Key Data
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Synonyms | BS, BSyn |
Gene | BLM |
Gene product | BLM DNA RecQ 3′-5′ helicase |
Function | Part of the RECQ helicases that unwind the DNA double helix. BLM maintains genomic stability during the process of DNA replication by limiting sister chromatin exchange (SCE). |
Heredity | Autosomal recessive |
Prevalence | Unknown 1:48.000 in Ashkenazi Jews; 0.5% heterozygosity for the blmAsh mutation |
Genotype-phenotype correlation | Homozygous and compound heterozygous carriers of one of the 60 pathogenic variants of the BLM gene exhibit a similar phenotype. |
Penetrance | Unknown |
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Diagnosis
Indicative Findings
Confirming the Diagnosis
The diagnosis of “Bloom syndrome” is confirmed by molecular genetic evidence of a biallelic/homozygous pathogenic variant of the BLM gene and/or, if the molecular genetics are inconclusive, by the identification of an increased frequency of sister chromatid exchanges (SCE) by specific cytogenetic studies.
Differential Diagnoses
Clinical Presentation
Clinical Presentation
Predisposition to Cancer (Entities):
Multiple tumors develop with the same distribution pattern as in the healthy population but with an earlier onset.
Therapeutic Considerations
Surveillance Recommendations
Surveillance Recommendations
Evidence-based standards are lacking for early detection, particularly during childhood. The AACR consensus recommendations are listed below.