Townes-Brocks Syndrome

Townes-Brocks syndrome is a genetic condition that affects several parts of the body. The most common features of this condition are an obstruction of the anal opening (imperforate anus), abnormally shaped ears, and hand malformations that most often affect the thumb. Most people with this condition have at least two of these three major features.

Other possible signs and symptoms of Townes-Brocks syndrome include kidney abnormalities, mild to profound hearing loss, heart defects, and genital malformations. These features vary among affected individuals, even within the same family. Intellectual disability or learning problems have also been reported in about 10 percent of people with Townes-Brocks syndrome.

The prevalence of this condition is unknown, although one study estimated that it may affect 1 in 250,000 people. It is difficult to determine how frequently Townes-Brocks syndrome occurs because the varied signs and symptoms of this disorder overlap with those of other genetic syndromes.

Mutations in the SALL1 gene cause Townes-Brocks Syndrome. The SALL1 gene is part of a group of genes called the SALL family. These genes provide instructions for making proteins that are involved in the formation of tissues and organs before birth. SALL proteins act as transcription factors, which means they attach (bind) to specific regions of DNA and help control the activity of particular genes. Some mutations in the SALL1 gene lead to the production of an abnormally short version of the SALL1 protein that malfunctions within the cell. Other mutations prevent one copy of the gene in each cell from making any protein. It is unclear how these genetic changes disrupt normal development and cause the birth defects associated with Townes-Brocks syndrome.

Read more about the SALL1 gene.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In some cases, an affected person inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.