Mitochondrial disorders are a significant cause of morbidity and mortality in the population. Here, we describe an adult patient with autosomal recessive myopathy and cardiomyopathy resulting from a complete loss of expression of the ADP/ATP translocase 1 (ANT1), a mitochondrial molecule which mediates ADP/ATP exchange between cytosol and mitochondria through the inner mitochondrial membrane. Skeletal muscle showed a dramatic proliferation of abnormal mitochondria, increased mitochondrial mass, and multiple mitochondrial DNA deletions. The patient’s heterozygous mother had normal clinical and pathological features. This report emphasizes the crucial role of the mitochondrial ADP/ATP carriers in muscle function and pathophysiology of human myopathies. (By Andoni Echaniz-Laguna, http://jmg.bmj.com/content/early/2011/12/19/jmedgenet-2011-100504.abstract?papetoc )