Quite recently, details have been revealed from two patients of five exhibiting contiguous gene syndrome (CGS) associated with deletions of the XK gene responsible for McLeod syndrome (OMIM 314850) and the ornithine transcarbamylase (OTC) gene responsible for OTC deficiency (OTCD [OMIM 311250]) [4]. Here, XK is linked to ornithine carbamoyltransferase deficiency.