ITPA and Infantile encephalopathy: Today, with two examples of lethality due to severe homozygous ITPA defects (Itpa knockout mouse data [6] and infantile encephalopathy data [32]), along with an example of increased fitness due to potential ITPA overexpression (TB susceptibility data [44]), it seems more likely that there is a spectrum of ITPA-related disease as Kevelam et al suggested [32].