PATIENTS WITH FEATURES SIMILAR TO HUNTINGTONS-DISEASE, WITHOUT CAG EXPANSION IN HUNTINGTIN

Objective: To describe characteristics of gene-negative patients with clinical features of Huntington's disease (HD), exploring Likely etiol ogies. Background: When a direct gene test became definitive for diagn osis of HD, we discovered a number of patients in our clinics in Balti more, MD, and Cambridge, UK, believed or suspected to have HD who did not have the triplet repeat expansion. Methods: Patients were examined using standardized instruments, and given full neurologic and psychia tric evaluations. Those negative for HD were tested for dentatorubro-p allidoluysian atrophy, SCA-1, SCA-3, SCA-2, SCA-6, and other condition s as indicated. Results: Of 15 patients, 7 received specific diagnoses or appear to be sporadic cases, 4 have a possible but uncertain relat ion to HD, and 4 have unknown familial progressive movement disorders. Conclusions: This last group of patients might be properly described as phenocopies of HD, some of which may be caused by unidentified trip let repeat expansions.