title: Development of left ventricular hypertrophy in adults in hypertrophic cardiomyopathy caused by cardiac myosin-binding protein C gene mutations.
abstract: OBJECTIVE
  We sought to determine whether the development of left ventricular hypertrophy (LVH) can be demonstrated during adulthood in genetically affected relatives with hypertrophic cardiomyopathy (HCM).
  
  
  BACKGROUND
  Hypertrophic cardiomyopathy is a heterogeneous cardiac disease caused by mutations in nine genes that encode proteins of the sarcomere. Mutations in cardiac myosin-binding protein C (MyBPC) gene have been associated with age-related penetrance.
  
  
  METHODS
  To further analyze dormancy of LVH in patients with HCM, we studied, using echocardiography and 12-lead electrocardiography, the phenotypic expression caused by MyBPC mutations in seven genotyped pedigrees.
  
  
  RESULTS
  Of 119 family members studied, 61 were identified with a MyBPC mutation, including 21 genetically affected relatives (34%) who did not express the HCM morphologic phenotype (by virtue of showing normal left ventricular wall thickness). Of these 21 phenotype-negative individuals, 9 were children, presumably in the prehypertrophic phase, and 12 were adults. Of the 12 adults with normal wall thickness < or = 12 mm (7 also with normal electrocardiograms), 5 subsequently underwent serial echocardiography prospectively over four to six years. Of note, three of these five adults showed development of LVH in mid-life, appearing for the first time at 33, 34 and 42 years of age, respectively, not associated with outflow obstruction or significant symptoms.
  
  
  CONCLUSIONS
  In adults with HCM, disease-causing MyBPC mutations are not uncommonly associated with absence of LVH on echocardiogram. Delayed remodeling with the development of LVH appearing de novo in adulthood, demonstrated here for the first time in individual patients with prospectively obtained serial echocardiograms, substantiates the principle of age-related penetrance for MyBPC mutations in HCM. These observations alter prevailing perceptions regarding the HCM clinical spectrum and family screening strategies and further characterize the evolution of LVH in this disease.
authors.affiliation: Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, Minnesota 55407, USA. hcm.maron@mhif.org
authors.forename: B J
authors.initials: BJ
authors.lastname: Maron
authors.forename: H
authors.initials: H
authors.lastname: Niimura
authors.forename: S A
authors.initials: SA
authors.lastname: Casey
authors.forename: M K
authors.initials: MK
authors.lastname: Soper
authors.forename: G B
authors.initials: GB
authors.lastname: Wright
authors.forename: J G
authors.initials: JG
authors.lastname: Seidman
authors.forename: C E
authors.initials: CE
authors.lastname: Seidman
mesh_terms: D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000000981:diagnostic imaging / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D004562:Electrocardiography / Q000379:methods; D005192:Family Health; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D019683:Penetrance; D010641:Phenotype; D011446:Prospective Studies; D014463:Ultrasonography; D000099163:Myosin Binding Protein C
chemical_list: D002352:Carrier Proteins; D000099163:Myosin Binding Protein C