Genetic characterization of a large, historically significant Utah kindred with facioscapulohumeral dystrophy.

In 1950, Tyler and Stephens reported a remarkable kindred affected with facioscapulohumeral dystrophy (FSHD), consisting of 1249 descendants of a man who emigrated to Utah in 1840. Members of this kindred are still seen in our clinic and, to our knowledge, no member had been tested for deletions at the FSHD1A locus on chromosome 4q35, the common chromosomal rearrangement associated with FSHD. We have identified 971 additional members of this kindred who either were not included in or unborn at the time of the report by Tyler and Stephens, and have identified 120 living members as affected by history or by examination. Members of this kindred contribute to a disease prevalence of nearly 1:15 000 in the Utah/southern Idaho region. We have demonstrated that affected members carry a disease-associated 20 kb deletion allele at the FSHD1A locus. This allele is the same size in multiple, distantly-related branches of the kindred, confirming the meiotic stability of the FSHD1A deletion. This large, genetically homogeneous population of patients represents a unique resource with which to study current questions about FSHD, including the possibilities of anticipation and parental transmission effects.