Patients with features similar to Huntington's disease, without CAG expansion in huntingtin.

Abstract

To describe characteristics of gene-negative patients with clinical features of Huntington's disease (HD), exploring likely etiologies. When a direct gene test became definitive for diagnosis of HD, we discovered a number of patients in our clinics in Baltimore, MD, and Cambridge, UK, believed or suspected to have HD who did not have the triplet repeat expansion. Patients were examined using standardized instruments, and given full neurologic and psychiatric evaluations. Those negative for HD were tested for dentatorubro-pallidoluysian atrophy, SCA-1, SCA-3, SCA-2, SCA-6, and other conditions as indicated. Of 15 patients, 7 received specific diagnoses or appear to be sporadic cases, 4 have a possible but uncertain relation to HD, and 4 have unknown familial progressive movement disorders. This last group of patients might be properly described as phenocopies of HD, some of which may be caused by unidentified triplet repeat expansions.