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J Med Genet 2005;42:e59 doi:10.1136/jmg.2005.033886
  • Electronic letters

Compound and double mutations in patients with hypertrophic cardiomyopathy: implications for genetic testing and counselling

  1. J Ingles1,
  2. A Doolan1,
  3. C Chiu1,
  4. J Seidman3,
  5. C Seidman3,
  6. C Semsarian2
  1. 1Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Sydney, Australia
  2. 2Department of Cardiology, Royal Prince Alfred Hospital, Sydney
  3. 3Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
  1. Correspondence to:
 Associate Professor Christopher Semsarian
 Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Locked Bag 6, Newtown, NSW 2042, Australia; c.semsariancentenary.usyd.edu.au
  • Received 11 April 2005
  • Accepted 13 May 2005
  • Revised 11 May 2005

Abstract

Objective: To report the frequency of single and multiple gene mutations in an Australian cohort of patients with hypertrophic cardiomyopathy (HCM).

Methods: Genetic screening of seven HCM genes (β-MHC, MyBP-C, cTnT, cTnI, ACTC, MYL2, and MYL3) was undertaken in 80 unrelated probands. Screening was by denaturing high performance liquid chromatography and direct DNA sequencing. Clinical data were collected on all patients and on genotyped family members.

Results: 26 mutations were identified in 23 families (29%). Nineteen probands (24%) had single mutations (11 β-MHC, 4 MyBP-C, 3 cTnI, 1 cTnT). Multiple gene mutations were identified in four probands (5%): one had a double mutation and the others had compound mutations. Six of 14 affected individuals from multiple mutation families (43%) experienced a sudden cardiac death event, compared with 10 of 55 affected members (18%) from single mutation families (p = 0.05). There was an increase in septal wall thickness in patients with compound mutations (mean (SD): 30.7 (3.1) v 24.4 (7.4) mm; p<0.05).

Conclusions: Multiple gene mutations occurring in HCM families may result in a more severe clinical phenotype because of a “double dose” effect. This highlights the importance of screening the entire panel of HCM genes even after a single mutation has been identified.

Footnotes

  • Competing interests: none declared

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