The Incidence of the 22q.11.2 Deletion Syndrome in children in Cape Town, South Africa

  • Dr John Lawrenson, Western Cape Paediatric Cardiac Services, South Africa
  • Dr Rik De Decker, Western Cape Paediatric Cardiac Services, South Africa
  • Dr Liesl Zuhlke, Western Cape Paediatric Cardiac Services, South Africa
  • Dr Zandre De Decker, Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, South Africa
  • Mardelle Schoeman, 2Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, South Africa
  • Glynis Schutte, 3National Health Laboratory Service, Groote Schuur Hospital, Cape Town, South Africa


    • Previous estimates of the prevalence of the 22q11.2 deletion syndrome in a paediatric cardiac clinic population were based on a retrospective review at our institution. This prevalence had increased in 2006 to a peak of 1.8% of the new patients seen at this centre. However, in the face of marked phenotypic variability, concern existed that the diagnosis may be missed in many patients.
    Aims
    1. To determine the incidence of the 22q11.2 deletion syndrome in a cohort of patients with congenital heart disease presenting to a tertiary cardiology referral centre.
    2. To assess an international scoring system for clinical recognition of the 22q11.2 deletion syndrome in cardiac patients.
    Methods
    All new patients with a significant congenital cardiac lesion were assessed for recruitment to the study. Once consent was obtained, all children were tested for the 22q11.2 deletion by the standard TUPLE1 fluorescent-in-situ-hybridisation (FISH) probe. All children were assigned a clinical “O score” at presentation(Oskarsdöttir 2005)

    Results
    To date 88 patients have been recruited and FISH tested; 69 (78.4%) FISH tests have been reported, and 4 (5.8%) are deleted. The mean O score of these 4 positive patients on presentation was 2.5.A cohort of seven patients was identified with clear clinical features of 22q deletion syndrome but FISH-negative.

    Conclusions
    Preliminary results of this study suggest that the 22q11.2 deletion is almost three times more than anticipated.The international clinical scoring system used to assess the need for FISH testing was not to apply to our patient population.