Rare hypertrophic cardiomyopathy

Rare hypertrophic cardiomyopathy (HCM) refers to a group of uncommon forms of hypertrophic cardiomyopathy that do not fall into the more frequently encountered genetic subtypes. Hypertrophic cardiomyopathy is characterized by abnormal thickening (hypertrophy) of the heart muscle, particularly the walls of the left ventricle, without an identifiable external cause such as high blood pressure or aortic valve disease. This thickening can impair the heart's ability to relax and fill with blood properly (diastolic dysfunction) and, in some cases, can obstruct blood flow out of the heart (left ventricular outflow tract obstruction). The rare forms grouped under this Orphanet classification (ORPHA:217569) encompass HCM caused by less commonly implicated genes or with atypical clinical presentations. Key symptoms may include exertional dyspnea (shortness of breath during physical activity), chest pain, palpitations, exercise intolerance, dizziness, syncope (fainting), and fatigue. In some patients, the disease may be asymptomatic and discovered incidentally through cardiac imaging or family screening. A serious concern in all forms of HCM is the risk of sudden cardiac death due to ventricular arrhythmias, particularly in younger individuals and athletes. The cardiovascular system is the primary system affected, though secondary effects on the pulmonary system (due to heart failure) and neurological symptoms (due to reduced cardiac output) may also occur. Treatment of rare hypertrophic cardiomyopathy follows general HCM management principles and is tailored to the individual patient's symptoms and risk profile. Beta-blockers and calcium channel blockers are commonly used to manage symptoms by reducing heart rate and improving diastolic filling. For patients with significant outflow tract obstruction, septal reduction therapies (surgical myectomy or alcohol septal ablation) may be considered. More recently, cardiac myosin inhibitors such as mavacamten have been approved for symptomatic obstructive HCM. Implantable cardioverter-defibrillators (ICDs) are recommended for patients at high risk of sudden cardiac death. Genetic counseling and family screening are important components of care given the hereditary nature of most forms of HCM.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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