Patients with biallelic mutations in ASNA1 present with severe cardiomyopathy within the first weeks of life, that is characterized by rapid clinical deterioration resulting in cardiorespiratory failure and early death. The cardiomyopathy may be accompanied by atrial or ventricular septal defects.
Histopathologic features include prominent subendothelial fibrosis, myofibrillar disorganization and intercalated disc abnormalities.