Which of the following is a common initial complaint in children with hypertrophic cardiomyopathy?

Dyspnea, or difficulty breathing, is indeed a common initial complaint in children with hypertrophic cardiomyopathy (HCM). In this condition, the heart muscle becomes abnormally thick, which can obstruct blood flow and affect the heart's ability to pump effectively. As a result, children may experience shortness of breath during physical activity or even at rest. This symptom often leads to reduced exercise tolerance and can be an early warning sign of the underlying condition.

Chest pain can occur in some patients but is not as prevalent as dyspnea in pediatric cases of HCM. Edema, or swelling, is typically more associated with heart failure and may not be an early sign in children. Fever is not related to HCM; it would more likely indicate an infection or inflammatory process rather than a primary cardiac condition. Thus, dyspnea stands out as the most relevant initial complaint associated with hypertrophic cardiomyopathy in children.