Cosegregation of KCNN4 gene mutations with HX phenotype. Patients in kindred 1 were assigned the diagnosis of HX (filled half circles) by clinical, laboratory, and biochemical methods.^4-6  The KCNN4 gene mutation detected by exome sequencing cosegregated with disease phenotype in all affected HX individuals examined. Inheritance of the KCNN4 mutation is heterozygous.