In DSM-IV, this disorder is called Dementia Due to Huntington's Disease
For more information, see Dementia Due to Other General Medical Conditions
The essential feature of Dementia Due to Huntington's Disease is the presence of a dementia that is judged to be the direct pathophysiological consequence of Huntington's disease. Huntington's disease is an inherited progressive degenerative disease of cognition, emotion, and movement. The disease affects men and women equally and is transmitted by a single autosomal dominant gene on the short arm of chromosome 4. The disease is usually diagnosed in the late 30s to early 40s but may begin as early as age 4 years in the juvenile form or as late as age 85 years in the late-onset form. The onset of Huntington's disease is often heralded by insidious changes in behavior and personality, including depression, irritability, and anxiety. Some individuals present with abnormalities of movement that resemble increased fidgeting and that later progress to characteristic generalized choreoathetosis. Difficulties with memory retrieval, executive functioning, and judgement are common early in the course, with more severe memory deficits occurring as the disease progresses. Disorganized speech and psychotic features are sometimes present. Late in the disease, characteristic "boxcar ventricles" may be seen on structural brain imaging due to the atrophy of the striatum. Position-emission tomography (PET) may show striatal hypometabolism early in the disease. Offspring of individuals with Huntington's disease have a 50% change of developing the disease. A genetic test is available to determine with relative certainty whether a given at-risk individual is likely to develop the disease; however, such testing may be best administered by centers with experience in counseling and follow-up of individuals at risk for Huntington's disease.
For more information, see Major and Mild Neurocognitive Disorders
A. The criteria are met for major or mild neurocognitive disorder.
B. There is insidious onset and gradual progression.
C. There is clinically established Huntington's disease, or risk for Huntington's disease based on family history or genetic testing.
D. The neurocognitive disorder is not attributable to another medical condition and is not better explained by another mental disorder.
Other mental disorders
Early symptoms of Huntington's disease may include instability of mood, irritability, or compulsive behaviors that may suggest another mental disorder. However, genetic testing or the development of motor symptoms will distinguish the presence of Huntington's disease.
The early symptoms of Huntington's disease, particularly symptoms of executive dysfunction and impaired psychomotor speed, may resemble other neurocognitive disorders (NCDs), such as major or mild vascular NCD.
Other movement disorders
Huntington's disease must also be differentiated from other disorders or conditions associated with chorea, such as Wilson's disease, drug-induced tardive dyskinesia, Sydenham's chorea, systemic lupus erythematosus, or senile chorea. Rarely, individuals may present with a course similar to that of Huntington's disease but without positive genetic testing; this is considered to be a Huntington's disease phenocopy that results from a variety of potential genetic factors.