The boundaries between myopathies, lower motor neuron disease and central nervous system disorders have recently become blurred, with the discovery of a CHCHD10 mutation in mitochondrial myopathy associated with FTD/ALS (OMIM #615911), whereas the allelic disorder, SMAJ, causes a mild lower motor neuron disease and no cognitive decline. The gene discussed is CHCHD10; the disease is Mental deterioration.