We describe the case of a Sardinian female child affected by SMARD1, a genetic composite heterozygote, in whom a new nonsense mutation (R788X) was found. A sister was affected by generalized muscular hypotonia and died from respiratory insufficiency at the age of 9 months, before a diagnostic definition had been formulated. Our patient died at 6 months due to respiratory insufficiency. At autopsy some differences with previous published cases were observed. In fact, our case is to the best of our knowledge the first report of giant cell hepatitis and myocarditis in SMARD1-affected patients, although this could be a chance association.