What is the most likely diagnosis for a young athlete who suddenly collapses and has a family history of sudden cardiac death?

The scenario described—where a young athlete suddenly collapses and has a family history of sudden cardiac death—strongly suggests a diagnosis of hypertrophic cardiomyopathy. This condition is characterized by an abnormal thickening of the heart muscle, which can lead to dynamic left ventricular outflow obstruction and arrhythmias. It is the most common cause of sudden cardiac death in young competitive athletes.

The familial aspect is also significant, as hypertrophic cardiomyopathy is often inherited in an autosomal dominant pattern, meaning it can run in families. Symptoms can range from asymptomatic to syncope, especially during exertion, which aligns with the athlete's sudden collapse.

The other conditions listed can also be associated with sudden cardiac events in young individuals, but they are less synonymous with the clinical picture provided. For example, Brugada syndrome is primarily associated with a specific ECG pattern and is more common in males of Southeast Asian descent, rather than having a broad association with athletic events. Arrhythmogenic right ventricular dysplasia can cause arrhythmias but is less frequently diagnosed than hypertrophic cardiomyopathy in this demographic. Long QT syndrome, while notable for causing syncope and arrhythmias, tends not to be as commonly linked with a history of sudden cardiac death in