Objective: To describe a second family with benign hereditary chorea (BCH, OMIM 118700) and suggestive linkage to chromosome 14q. BCH is an autosomal dominant disorder of early onset that differs from Huntington disease in being nondementing and nonprogressive without other neurologic signs. There has been controversy regarding the existence of BCH as a discrete disorder.
Background: A single kindred was recently reported with linkage of BCH to a 20.6-KcM region on chromosome 14q.
Methods: In a four-generation family with BCH, linkage was evaluated to markers in a 23-KcM region between D14S49 and D14S66 that contains the putative BCH locus.
Results: A multipoint nonparametric lod score of 3.01 is consistent with linkage of disease in this family to the 14q BCH locus. A recombination event in one affected individual enabled the critical region to be narrowed to 6.93 KcM flanked by D14S1068 and D14S1064. This region contains two candidate genes: glial maturation factor beta and guanosine triphosphate cyclohydrolase 1 (GCH1). Survival motor neuron (SMN) interacting protein-1 is eliminated as a candidate gene because it lies outside the critical region. No sequence alteration was identified in the coding region of GCH1 in an affected individual.
Conclusion: These data provide further evidence that BCH is a distinct entity, narrow the location of BCH to a 6.93-KcM region on chromosome 14q, and exclude SMN interacting protein-1 as a candidate gene.