RAB18 and Micro syndrome: Warburg Micro syndrome, also called Micro syndrome, was first described in 1993.[1] So far, mutations in four genes that encode Ras-associated binding proteins and regulators have been associated with this syndrome: RAB3GAP1 (NM_001172435),[5,6]RAB3GAP2 (NM_012414),[7]RAB18 (NM_001256410)[8] and TBC1D20 (NM_144628).[9] The syndrome appears to occur most frequently in association with RAB3GAP1 mutations, which occur in approximately 40% of all patients.[10]