Deficiency of the mitochondrial phosphate carrier presenting as myopathy and cardiomyopathy in a family with three affected children

► The mitochondrial phosphate carrier SLC25A3 is expressed in tissue specific isoforms by alternative splicing. ► We identified a novel mutation of the SLC25A3 in three children with a neonatal onset of cardiomyopathy and myopathy. ► The mutation affects the alternatively spliced exon 3A specific for heart and muscle. ► It broadens the clinical spectrum of this disease since patients may survive into adulthood.