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. The gene discussed is VMA12; the disease is Cognitive impairment.