As a result, genetic testing is the only way to confirm the syndrome.BHC is caused by a single-nucleotide substitution mutation in TITF1, which encodes thyroid transcription factor 1 (TTF-1) and is inherited in an autosomal dominant pattern. This gene is also known as NK2 homeobox 1 (NKX2-1) The single-nucleotide substitution mutation then ultimately has drastic effects on the maturation processes of TITF-1In some cases, additional developmental abnormalities of lung and thyroid tissue are found in BHC, leading to the suggested alternative name brain-lung-thyroid syndrome. Genetics
Benign Hereditary Chorea is an autosomal dominant disorder. It is believed to be caused by a single-nucleotide substitution in TITF1, located on chromosome 14. A wide spectrum of mutations have been reported, drawing a potential association between amount of subsequently deleted nucleotides to severity of symptoms. These mutations lead to protein truncation, prevent DNA binding, and a loss-of-function. Mutations of the gene affect namely the lungs, brain, and thyroid. This is because during embryonic development, NKX2.1 plays a key role in binding to transcriptional regulatory elements and proteins within those respective organs. Diagnosis
BHC begins showing symptoms during childhood, and is commonly a familial disorder. This is a disorder that is correlated with mutations in the thyroid transcription factor gene (TITF-1). The disorder was discovered in the 1960s. During the time of its discovery, there were no tests that could be used to confirm a diagnosis of the disorder, and the phenotype was not easy to distinguish from other disorders. This resulted in the existence of the disorder being questioned.
Currently, BHC is diagnosed through the identification of the phenotypic symptoms with a genetic test to confirm the mutation in the TITF-1 gene. Management
There are no cures for benign hereditary chorea, but there are several medications that have been shown to treat the symptoms of the disorder. Levodopa has been shown to improve the effects of chorea on a patients gait within 6 weeks of starting treatments. However, this medication did have the side effect of "dose-dependent dyskinesia." Methylphenidate has also been used to improve chorea symptoms. Steroids have been used to treat BHC, but due to the presence of dystonia, it is questionable whether these patients actually had BHC. Epidemiology
In 1978, BHC was reported to have a frequency of 1:500,000 within a Welsh population, but due to how some symptoms are hard to distinguish, it was concluded that the number is underrespresentative of actual clinical cases. Results for correlation between sex and distribution of the disorder are inconclusive. See also
Chorea
Huntingtons disease

References


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