In HIDS, most of the MK mutations affect stability or folding of the encoded mutant protein.3 In MA, mutations must have a more deleterious effect on MK protein folding and/or may direct effect MK catalytic properties.31 Besides, the residual activity of MK enzyme can be manipulated by environmental conditions; temperature worsens the folding defect.31,33 This must be clinically relevant in febrile patients, and could explain why ear-nose-throat (ENT) infection is a triggering factor of MKD attacks. This evidence concerns the gene MVK and mevalonic aciduria.