Coenzyme Q (CoQ10) is an essential mitochondrial electron carrier, redox cofactor and a potent antioxidant in the majority of cellular membranes. A range of metabolic diseases, as well as the ageing process and prolonged statin treatments have been associated with CoQ10 deficiency. Here the first case of a primary CoQ10 defect due to a mutation in COQ7, necessary for CoQ10 biosynthesis, is presented. For accurate diagnosis a novel and highly sensitive method for CoQ10 quantification by UPLC – mass spectrometry was developed. By applying the COQ10 analogue, 2,4-dihydroxybenzoic acid, a potentially effective treatment strategy for CoQ10 deficiencies is introduced. (By Dr. Christoph Freyer, http://jmg.bmj.com/content/early/2015/06/16/jmedgenet-2015-102986 )