Penetrance of Hypertrophic Cardiomyopathy in Children and Adolescents

Abstract

Background— The penetrance of hypertrophic cardiomyopathy (HCM) during childhood and adolescence has been only sparsely described. We studied the penetrance of HCM and the short- and long-term outcomes of clinical screening and predictive genetic testing of child relatives of patients with HCM. Methods and Results— Ninety probands and 361 relatives were included in a family screening program for HCM (1994–2001). Eleven sarcomere genes, CRYAB, α-GAL, and titin were screened. Sixty-six relatives and 4 probands were <18 years of age at inclusion. Twelve child relatives were mutation carriers (age, 12 ± 5 years), and 26 had unknown genetic status, ie, relatives from families without identified mutations (n = 21) or not tested (n = 5) (age, 11 ± 5 years). Twenty-eight noncarriers (42%; age, 10 ± 4 years) served as control subjects. Two of 38 child relatives (5%) at risk of developing HCM fulfilled diagnostic criteria for HCM at inclusion. After 12 ± 1 years of follow-up, 2 of the 36 (6%; 95% confidence interval, 2–18) at-risk child relatives who were phenotype negative at inclusion had developed the HCM phenotype at 26 and 28 years of age. During follow-up, none of the child relatives experienced serious cardiac events. Participation in the screening program had no long-term negative psychological impact. Conclusions— The penetrance of HCM in phenotype-negative child relatives at risk of developing HCM was 6% after 12 years of follow-up. The finding of phenotype conversion in the mid-20s warrants continued screening into adulthood. Forty-two percent of the child relatives were noncarriers, and repeat clinical follow-up could be safely limited to the remaining children.