Which are the causes of Benign Hereditary Chorea BHC?

Benign Hereditary Chorea (BHC) is a rare genetic disorder characterized by involuntary movements, specifically chorea, which is the jerky, uncontrolled movement of the limbs, face, and other body parts. BHC is inherited in an autosomal dominant manner, meaning that an affected individual has a 50% chance of passing the condition on to each of their children.

The primary cause of BHC is a mutation in the TITF1 gene, also known as NKX2-1, which is responsible for providing instructions for the production of a protein called thyroid transcription factor 1. This protein plays a crucial role in the development and function of certain cells in the brain, thyroid, and lungs. Mutations in the TITF1 gene disrupt the normal functioning of these cells, leading to the characteristic symptoms of BHC.

Although the exact mechanism by which TITF1 mutations cause BHC is not fully understood, it is believed that the abnormal protein disrupts the balance of chemicals in the brain, particularly dopamine, which is involved in the regulation of movement. The imbalance of dopamine leads to the involuntary and uncoordinated movements seen in individuals with BHC.

BHC is an autosomal dominant disorder, meaning that a person only needs to inherit one copy of the mutated gene from either parent to develop the condition. In some cases, the mutation occurs spontaneously during the formation of reproductive cells or early embryonic development, without being inherited from either parent.

It is important to note that individuals with BHC have a 50% chance of passing the condition on to each of their children. Genetic counseling and testing can help individuals and families understand the risks and make informed decisions about family planning.

While the specific cause of BHC is known to be the TITF1 gene mutation, there may be other genetic and environmental factors that influence the severity and progression of the disorder. Ongoing research aims to identify additional genes or factors that may contribute to the development of BHC and provide a better understanding of the condition.