Mevalonate Kinase Deficiency (MKD)/Hyperimmunoglobulin D With Periodic Fever Syndrome (HIDS) (OMIM #260920) is a rare autosomal recessive SAID characterised by bi-allelic mutations in the mevalonate kinase (MVK) gene (12q24.11) resulting in defective cholesterol biosynthesis and increased urinary excretion of mevalonic acid (53). Here, MVK is linked to hyperinsulinemic hypoglycemia, familial, 4.