The features of Barth syndrome are very variable but the majority of patients develop heart failure (cardiomyopathy) within the first year. Heart failure in young children tends to cause rapid, laboured breathing and poor feeding. Sweating with feeds is common. The heart tends to be swollen like a floppy bag (called dilated cardiomyopathy or DCM), and may have a thickened white inner lining (known as endocardial fibroelastosis or EFE) or deep pockets in the wall of one of the major pumping chambers (called left ventricular non-compaction or LVNC). Potentially serious cardiac rhythm problems may occur and there may be a previous family history of sudden death.
The blood neutrophil count varies unpredictably between low and normal but can be normal at all times in 10% of affected males. When it is very low (termed severe neutropenia), boys may develop sore red gums (complaining when their teeth are brushed), mouth ulcers, nappy rashes and bacterial infections. Muscles are weak and affected babies are often slow to sit, walk or run (called 'delayed motor milestones' or 'motor delay'). They may have difficulty when rising from sitting on the floor, have a rather waddling gait on running and difficulty in kicking a football.