Huntington's Disease (HD)

Case Study A
A 32-year-old male Caucasian, who was lively and talkative as a child, completed high school with As and Bs and four years of college with poor grades. At age 22 he became quiet and non-conversant. At age 24 he began work as a cook/dishwasher and displayed noticeable uncoordination. At age 28 he developed dysarthria, dysphagia, stiffness, slow ataxic gait, and dementia. There was no history of schizophrenia or depression and the neurological review of systems was negative. Both parents were in their late 60s and in excellent health, without signs of dementia. There was no family history of any neurodegenerative disease, and he had three sisters, ages 35-37, all in good health.

Laboratory results showed normal CPK, vitamin E, lactate, and pyruvate levels. The patient's MRI revealed a generalized, cerebral and cerebellar atrophy and a very small caudate nuclei. Two skin biopsies showed normal mitochondria on histology. Bone marrow analysis and enzyme screens for Gm, HGM, MLD, and Krabbe's disease were all normal. During the physical exam the patient scored a 20/26 on the mini-mental status exam. The cranial nerve exam was remarkable for decreased upgaze, saccadic extraocular eye movements, dysarthria and hyperactive gag reflex. There was increased tone in all extremities with normal strength and gait was wide-based and ataxic.

A Huntington's Disease DNA test was ordered; the patient's PCR analysis demonstrated two bands, one normal band at 23 CAG repeats and an abnormal band of 49 CAG repeats. A diagnosis of HD was made. The patient's parents were also tested. His father showed a normal band of 20 CAG repeats and a band within the borderline range of 37 CAG repeats. One sister received a predictive test that was found to be negative.