SLC12A3 and Gerstmann syndrome: GS is an autosomal recessive disorder caused by loss-of-function mutations in SLC12A3 (24), and the majority of patients exhibit homozygous or compound heterozygous mutations of SLC12A3. However, based on SLC12A3 mutation screening, 18–40% of GS patients are typically found to carry only one mutant allele (1, 14, 24, 27).