Chromosome Breakage Studies

Description: 
Fanconi anaemia:
The test detects defective DNA repair in response to alkylating agents by screening for increased spontaneous and mutagen induced chromosome breakage. The primary mutagen used is Diepoxybutane (DEB) which we find gives the best discrimination between affected and unaffected individuals but Mitomycin C (MMC) testing is available on request.
Radiosensitivity syndromes:
Ataxia-telangiectasia and Nijmegen breakage syndrome patients are defective for repair of ionising radiation induced damage. Raised spontaneous and gamma ray induced chromosome breakage is screened for and G-banded metaphase preparations are examined for clonal chromosome rearrangements, particularly involving the immunoglobulin genes on chromosomes 7 and 14.
Clinical details: 
Our genetics laboratory is a supra-regional and international reference laboratory for chromosome instability testing by cytogenetic techniques: our experience encompasses the full range of classical and atypical cases reported in the literature. Specific testing strategies for the different disorders are employed to look for raised spontaneous and specific mutagen-induced damage and/or chromosome rearrangements or other anomalous behaviour. We offer both pre- and postnatal diagnosis on amniotic fluid, chorionic villi, blood and solid tissue samples.
Related condition or disease: 
Other rare syndromes:
Bloom syndrome: This test looks for a greatly increased frequency of sister chromatid exchanges (SCEs) in cultured cells.
Roberts syndrome (SC Phocomelia): Screening cultured cells for premature centromere separation and the presence of random aneuploidy.
Premature chromosome condensation: An increased incidence of prometaphase cells is indicative of the presence of a mutation in the microcephalin gene MCPH1 and identifies patients for specific mutation testing.
ICF syndrome: Immunodeficiency, Centromeric region instability, and Facial anomalies syndrome is characterised by deletions and rearrangements involving the
centromeric heterochromatic region of chromosomes, particularly chromosomes 1, 9, and 16, which can be screened for in mitogen-stimulated lymphocyte cultures.
Other syndromes: We can perform cytogenetic screening for raised levels of spontaneous chromosome breakage, chromosome rearrangements and aneuploidy. This may be of benefit if rare instability syndromes such as Werner syndrome and variegated aneuploidy syndrome are suspected, or if a defect in chromosome repair or processing is suspected in a patient with unusual presentation.
Synonyms or keywords: 
Chromosome breakage, chromosome instability, Fanconi anaemia, Diepoxybutane, DEB test, Mitomycin C, MMC, Radiosensitivity syndromes, Ataxia-telangiectasia, Nijmegen breakage syndrome, Bloom syndrome, Roberts syndrome, SC Phocomelia, Premature chromosome condensation, MCPH1, ICF syndrome, Werner syndrome, variegated aneuploidy syndrome
Department: 
Genetics Department
Location: 
Guy's Hospital
Sample type and Volume required: 
Peripheral blood in a lithium heparin bottle, 5ml (2ml from babies). Amniotic fluid and solid tissue specimens in a dry sterile container (20ml), CVS (20mg please discuss with the laboratory). Cultured fibroblast cells are also accepted.
Call in advance: 
Please notify the laboratory before sending samples
Turnaround time: 
Routine – 42 days Urgent – 14 days Please indicate on the referral form whether urgent analysis is required along with supporting clinical information (neonates (<mth) and patients needing urgent treatment).
Special sample instructions: 

Request form available at https://southeastgenomics.nhs.uk/wp-content/uploads/2023/08/SE-GLH-Non-WGS-Genetic-Test-Request-Form-August-2023-v1.5.pdf

  • R258 Cytopenia - Fanconi breakage testing indicated.
  • R259 Nijmegen breakage syndrome.
  • R260 Fanconi anaemia or Bloom syndrome - chromosome breakage testing.
  • R294 Ataxia telangiectasia - DNA repair testing.

Include the relevant R code (above) on the referral form; for further details and the eligibility criteria for testing please see https://www.england.nhs.uk/publication/national-genomic-test-directories/

Criteria for acceptance / rejections of sample
Storage and transport: 
Samples should arrive within 72 hours (preferably24 hours) of sampling. For prenatal diagnosis please discuss with the laboratory before sending any samples.
Cost: 
On application
Time limit for extra tests: 
Do not spin down or freeze samples before sending.
Contacts:
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Cytogenetics Laboratory at Guy's

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Last updated: 26/10/2023