For a study, researchers sought to report the clinical presentation and natural history of individuals under the age of 12 who presented with nonsyndromic HCM. Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium were obtained and compared with data from 568 children between the ages of 12 and 16. At the start of the study, 339 patients (53.6%) had a family history of HCM, 132 (20.9%) experienced heart failure symptoms, and 250 (39.2%) were prescribed cardiac medicines. The median maximum left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), with 145 patients (27.2%) having a blocked left ventricular outflow tract. During a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) had cardiac transplantation, and 69 (10.8%) experienced life-threatening arrhythmic episodes. Compared to those who presented after 12 years, younger patients had a larger proportion of myectomy (10.5% vs. 7.2%; P=0.045), but fewer had primary prevention implanted cardioverter-defibrillators (18.9% vs. 30.1%; P=0.041). The death rate of life-threatening arrhythmic events did not change; however, the occurrences occurred at a younger age. Early-onset pediatric HCM had the same symptom load and cardiac profile as individuals who emerge later in childhood. In addition, long-term results, including death, did not differ by the age of presentation, while patients under the age of 12 encountered adverse events at a younger age.