MVK and periodic fever syndrome: A defect in the pre-squalene activity of mevalonate kinase (MK, encoded by the mevalonate kinase gene, MVK) induces periodic fever syndromes, with different degrees of severity depending on the residual activity of mevalonate kinase: the autoinflammatory hyper immunoglobulinemia D (MIM 260920) is characterized by a 1%–8% residual MK activity, while in mevalonic aciduria (MIM 610377) MK level activity is undetectable [13,14].