Cosegregation of FAM38A gene mutations with HX phenotype. The FAM38A gene mutations detected by exome sequencing in affected HX persons cosegregated with disease phenotype in all affected persons in both kindreds. Family A indicates New York pedigree. As predicted by clinical, genetic, and biochemical studies, the parents and affected HX persons are heterozygous for the FAM38A mutation and persons III-14, III-15, and III-21 are homozygous for the FAM38A mutation. Family B indicates Canadian pedigree. Inheritance of the FAM38A mutation is heterozygous. “NT” in the symbols indicates persons who were “not tested” and clinical, laboratory, biochemical, and genetic data are not available.