Benign hereditary chorea (BHC), also known as benign familial chorea, is a rare autosomal dominant neurogenetic syndrome. It typically presents itself in childhood with isolated chorea, with average to below average intelligence. Unlike other neurogenetic causes of chorea such as Huntingtons disease, BHC is not progressive, and not associated with cognitive decline or psychiatric problems in the vast majority of cases.The first description of BHC was reported in 1967 in an African American family from Mississippi. Two brothers reportedly had delayed motor development in childhood and were diagnosed with chorea. These findings were reaffirmed by other families reporting similar traits and an autosomal dominant pattern of inheritance was suggested. However, heterogeneity in the presentations of the affected individuals made confirmation of these diagnoses of BHC difficult to prove. Features reported in these families, including dystonia, tremor, and myoclonus, led researchers to question whether BHC actually represents different diagnoses with similar phenotypes inappropriately grouped together.Further research in 2000 confirmed a connection between a Dutch family reporting similar characteristics of BHC and one of the original families. The investigators identified a linkage to a disease locus on the long arm of chromosome 14 from this connection. Signs and Symptoms
Benign Hereditary Chorea is characterized by early onset of an abnormal gait, speech articulation difficulties, anxiety, and chorea.The clinical spectrum of symptoms resulting from BHC is vast, manifesting as thyroid agenesis to dysarthria to distress syndrome.
However, in 2002, the experimentally observed mutation of the gene leading to the BHC phenotype was identified, solidifying benign hereditary chorea as a disorder. In 1967, several families were examined and discovered to have movements that were abnormal and random since childhood. These random movements were not violent movements, and gave the person a "general appearance of restlessness." The movements occurred mostly in the hands and arms, and some also experienced them in their tongues, facial muscles, and lower body. Movements in the lower extremities, if severe enough, could cause changes in gait. The families were given a Wechsler Intelligence Scale test, scoring average relative to others in their community. Aside from the aforementioned symptoms, the peoples physical and neurological characteristics were normal. The observed symptoms were put in the category of chorea. Researchers made pedigrees of the families they studied and determined that BHC was an autosomal dominant disorder. By studying a Dutch family, the disorder was discovered to be linked to chromosome 14. In 2002, an Italian family was studied, and they had the same linkage to chromosome 14 as the Dutch family did. Looking closer at the region of the chromosome suspected of causing the disorder, researchers discovered that there was a 1.2 Mb deletion in the DNA that resulted in the loss of the TITF-1 gene. This meant that mutations in the TITF-1 gene were likely the reason behind the symptoms of BHC.