Age of HCM Diagnosis in Athletes
Left ventricular hypertrophy in HCM typically becomes evident during adolescence or early adulthood, with the mean age of sudden cardiac death in athletes with HCM being 17.1 years old. 1
Timing of Phenotypic Expression
Adolescence represents the critical period for HCM manifestation in athletes:
LV hypertrophy most commonly appears during accelerated body growth and maturation in the adolescent years, with morphologic expression usually completed by the time physical maturity is achieved (approximately 17-18 years of age) 1
The disease becomes phenotypically evident during adolescence or early adulthood in most cases, though it may not manifest until the 4th or 5th decades of life in some individuals 1
Children under 13 years old commonly remain "silent" mutation carriers without evidence of LV hypertrophy on echocardiography, even when harboring disease-causing genes 1
Age-Related Screening Data
Screening studies provide specific age-related diagnostic patterns:
In a large Italian screening program of 33,735 young athletes, HCM was detected in only 0.07% during preparticipation evaluation, with most diagnoses occurring during the adolescent to young adult period 2
Among screened soccer players aged 16-17 years followed for over 10 years, HCM-related cardiac deaths occurred in this age range, confirming adolescence as a high-risk period 1
The morphological overlap between physiological LV hypertrophy and HCM is less common in adolescent athletes (<1% in white athletes, up to 7% in African athletes) compared to adults 1
Clinical Implications for Screening
Guideline-recommended screening intervals reflect age-dependent risk:
Systematic screening should begin no later than age 12 years, or earlier if growth spurts, signs of puberty, plans for intense competitive sports, or malignant family history are present 1
Screening every 12-18 months is recommended throughout adolescence (ages 12-18 years) due to the dynamic nature of phenotypic expression during this period 1
After age 18-21 years, screening intervals can be extended to every 5 years in genotype-positive individuals without phenotypic expression, though late-onset adult conversions can occur even in middle age 1
Important Caveats
ECG abnormalities may precede structural disease by several years, meaning electrical changes can be detected before echocardiographic evidence of hypertrophy appears 1
A minority (5-10%) of young individuals with HCM may have a normal ECG, which can delay diagnosis in athletes undergoing screening 1
Late-onset phenotypic expression can occur, particularly with cardiac myosin-binding protein-C mutations, where de novo LV hypertrophy may appear in mid-life or later, meaning a normal echocardiogram at maturity does not definitively exclude HCM 1