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Online medical genetics in practice
Bayesian risk assessment for autosomal recessive diseases: fetal echogenic bowel with one or no detectable CFTR mutation
  1. S Ogino1,2,3,
  2. R B Wilson4,
  3. W W Grody5
  1. 1Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, USA
  2. 2Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
  3. 3Harvard Medical School, Boston, Massachusetts, USA
  4. 4Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, Philadelphia, USA
  5. 5Departments of Pathology and Laboratory Medicine, Human Genetics, and Pediatrics, UCLA School of Medicine, Los Angeles, California, USA
  1. Correspondence to:
 Dr Ogino
 Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 USA; soginopartners.org

https://doi.org/10.1136/jmg.2003.015065

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    Risk assessment is an essential component of genetic counselling and testing, and Bayesian analysis plays a central role in complex risk calculations.1–3 Prenatal risk assessment for autosomal recessive diseases can be particularly complex when, for example, only one mutation is detectable in the fetus, and when mutation detection rates and disease allele frequencies vary among different ethnic groups. A classic example is the risk assessment for a fetus with echogenic bowel and only one detectable mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The fetus could be affected or be a carrier on the basis of the presence of one detectable mutation. Accurate risk assessment in this scenario may be critical for parental decision making.

    Cystic fibrosis is the most common severe autosomal recessive disorder; it affects about one in 2500 live births and has a carrier frequency of about one in 25 among European Caucasians.4 Cystic fibrosis is caused by homozygous mutations in the CFTR gene (OMIM 602421; 219700 cystic fibrosis; CFTR mutation database (http://www.genet.sickkids.on.ca/cftr/)). More than 1000 different CFTR mutations have been reported, and the mutation frequencies vary in different ethnic groups. The ultrasound finding of echogenic bowel, which is present in 0.1–0.2% of all pregnancies, may result from fetal meconium ileus and can result from cystic fibrosis.5,6 The American College of Medical Genetics (ACMG) uses a panel of 25 CFTR mutations and advocates carrier screening for people with a family history of cystic fibrosis and their partners, as well as for all couples in the general population in whom the woman is pregnant or considering pregnancy.7 The clinical scenarios addressed in this paper are likely to be encountered with a high frequency. Despite the importance of accurate risk assessments in these scenarios, generalisable approaches to such risk assessments are …

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    Footnotes

    • Conflicts of interest: None declared.