Rs121912810

rs121912810, also known as p.Ser189Phe, is a mutation in the CLCN1 gene on chromosome 7.

Acting in an autosomal dominant manner, the rs121912810(T) allele is considered to cause Thomsen's myotonia congenita; see also OMIM 118425.0018

Note that 23andMe refers to this SNP as i5003253.