The patients with TMEM199-CDG described so far have displayed a strikingly similar clinical presentation, with hepatic features resembling other V-ATPase chaperone deficiency syndromes, however without associated symptoms such as hypogammaglobulinemia [13], epilepsy and cognitive impairment [11, 13] noted in the related syndromes. This evidence concerns the gene DNAH8 and Cognitive impairment.