In our paper, we report the identification of a de novo mutation in ISCU in a young male presenting ptosis, severe muscle weakness, and marked exercise intolerance. The first mutation in ISCU was described almost 10 years in Swedish patients while the second mutation was found the following year. No additional mutation in ISCU has been reported from then on. The associated disease is known as “Myopathy with lactic acidosis” and has an autosomal recessive inheritance. We identified the first heterozygous dominant ISCU mutation which results in a phenotype reminiscent of the recessive disease previously reported. (By Dr. Daniele Ghezzi, http://jmg.bmj.com/content/early/2017/10/27/jmedgenet-2017-104822 )