Yamaguchi syndrome, commonly referred to as apical hypertrophic cardiomyopathy, is an unusual subtype of hypertrophic cardiomyopathy predominantly involving the apical region of the left ventricle (1). Isolated involvement of the left ventricular apex is the most frequent radiological finding of this entity, nevertheless, involvement of the right ventricular apex has also been described (1). An estimated 25% of patients of Asian descent with a diagnosis of hypertrophic cardiomyopathy have Yamaguchi syndrome (2). In contrast, 1-10% of patients of non-Asian descent with a diagnosis of hypertrophic cardiomyopathy present the Yamaguchi subtype (2). It is important to highlight that research and scientific data regarding this topic in the general Hispanic population is scarce. Furthermore, epidemiologic trends pertaining to Yamaguchi syndrome specific to the Puerto Rican population have not been presented in literature. Understanding apical hypertrophic cardiomyopathy in the Puerto Rican population is essential as it can provide greater insight into an underserved population, ultimately improving access to appropriate clinical management. This is specifically significant as cardiovascular diseases represent the leading cause of death in Puerto Rico (3). 

Expanding the overview of Yamaguchi syndrome into diverse patient demographics implies understanding inheritance patterns, clinical manifestations, mimickers, and radiological findings. An autosomal inheritance pattern has been suggested in apical hypertrophic cardiomyopathy, specifically involving mutations of genes encoding for sarcomere proteins (4). Common symptoms associated with Yamaguchi syndrome include chest pain, palpitations, dyspnea, and syncope (5). Differentiating apical hypertrophic cardiomyopathy is essential as in some instances clinical symptoms of acute coronary syndrome may be mimicked, delaying adequate diagnosis (1). 

The radiological assessment of Yamaguchi syndrome involves a variety of imaging modalities such as echocardiography, ventriculography, computed tomography (CT), and magnetic resonance (MR) imaging (6). Apical wall thickness of 15 mm or greater, absence of apical tapering, and identification of precordial T wave inversion are highly suggestive of a diagnosis of this syndrome (6). Moreover, the focal hypertrophy of the apical region of the ventricle can result in the ace-of-spades appearance of the ventricular cavity which has been strongly associated with this syndrome (6). The most common patterns of late gadolinium enhancement seen in Yamaguchi syndrome are apical and subendocardial (7). Late gadolinium enhancement functions as a marker for myocardial fibrosis, aiding in determining the risk of heart failure and sudden cardiac death for patients with this entity (7). Particularly, late gadolinium enhancement involving 15% or more of the left ventricular mass increases the risk of major arrhythmic events and sudden cardiac death (8). Overall, it is important to consider that the application of multiple imaging modalities in combination with electrocardiography (ECG) ultimately leads to a more accurate assessment of Yamaguchi syndrome (9).