Uhl anomaly

Uhl anomaly, also known as parchment heart or partial or total absence of the right ventricular myocardium, is an extremely rare congenital heart defect characterized by the near-complete or complete absence of the muscular wall (myocardium) of the right ventricle. In this condition, the right ventricular wall is paper-thin, composed almost entirely of endocardium and epicardium without intervening muscle tissue. This results in a severely dysfunctional right ventricle that is unable to effectively pump blood to the lungs through the pulmonary circulation. The condition primarily affects the cardiovascular system. Key clinical features include severe right-sided heart failure, marked dilatation of the right ventricle, tricuspid regurgitation, cyanosis (bluish discoloration of the skin due to poor oxygenation), peripheral edema, hepatomegaly, and arrhythmias. Patients may present in the neonatal period or infancy with signs of congestive heart failure, though rare cases have been reported in older children and adults. The condition can mimic or overlap clinically with arrhythmogenic right ventricular cardiomyopathy (ARVC), though Uhl anomaly is considered a distinct entity because it involves congenital absence of myocardium rather than progressive fibrofatty replacement. Treatment options are limited and depend on the severity of the condition and the age at presentation. Medical management includes diuretics and medications to support cardiac function, but these are often insufficient. Surgical interventions may include the Glenn procedure or Fontan palliation, which redirect blood flow to bypass the dysfunctional right ventricle, effectively converting the circulation to a single-ventricle physiology. In severe cases, heart transplantation may be the only definitive treatment. The prognosis is generally poor, particularly in neonates presenting with severe heart failure, though survival into adulthood has been reported in milder cases.

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