MVK and hyperinsulinemic hypoglycemia, familial, 4: There are two forms of mevalonate kinase deficiency: mevalonic aciduria (MA), when residual function of the enzyme is undetectable (<1 % [3] or <0.5 % [8] according to different authors) and hyperimmunoglobulinemia D syndrome (HIDS), when residual function of the enzyme is 1.8–28 % [3, 9] (or 1–10 % [8]).