Biallelic loss-of-function variants in RAB18, RAB3GAP1, RAB3GAP2, or TBC1D20 cause the autosomal recessive condition Warburg Micro syndrome (4, 5, 6, 7, 8) (Mendelian Inheritance in Man IDs: 600118, 614222, 614225, 615663, and 212720). Here, RAB3GAP1 is linked to Micro syndrome.