Overview Symptoms & Causes Diagnosis & Treatments Programs & Services Contact Us What is Barth syndrome? Barth syndrome is metabolic disorder that affects the heart, muscles, immune system, and growth. It almost always occurs in boys. Barth syndrome usually appears during infancy or early childhood, but the age of onset can vary greatly. Children with Barth syndrome can develop serious heart problems including congestive heart failure, heart muscle weakness (cardiomyopathy), and serious arrhythmias. They can also have infection or sepsis. Barth syndrome affects about 1 in every 300,000 to 400,000 babies born worldwide.