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Condition report · Gastrointestinal

Townes-Brocks Syndrome

Whole genome sequencing reads the SALL1 gene for inherited changes that cause Townes-Brocks syndrome, a developmental condition that affects the anus, the thumbs and the ears.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A rare developmental condition that typically affects the anus, the thumbs and the ears, often with hearing loss and sometimes kidney or heart differences. It is caused by changes in one copy of the SALL1 gene.

Townes-Brocks syndrome is a rare developmental condition that typically affects the anus, the thumbs and the ears. The most common signs are an imperforate anus or narrowed anal opening, thumb differences such as an extra thumb or an extra joint, and ears that are shaped differently, often with skin tags in front of the ear and hearing loss. Kidney differences, heart defects and foot differences can also occur.

The condition is caused by a change in one copy of SALL1. This gene makes a protein that helps switch other genes on or off while the hands, ears, anus and kidneys form before birth. Most known changes shorten the protein, and kidney function can decline over time, which is why it is checked every year.

Townes-Brocks syndrome is inherited in an autosomal dominant way. Each child of an affected person has a 50% chance of inheriting the change, and about half of cases arise new in the affected person. Features in a parent can be mild, so genetic counselling and parental testing are recommended. Relatives at risk can then be identified early.

The condition we analyse

Autosomal dominant

Caused by a change in one copy of the SALL1 gene, which encodes a transcription factor that guides development of many organs. About half of cases are inherited from an affected parent and half arise de novo.

Signs and symptoms

An imperforate anus or other anal differences, thumb differences such as an extra joint (triphalangeal thumb) or an extra thumb, and unusually shaped ears, often with skin tags and hearing loss. Kidney differences occur and can lead to reduced kidney function. Foot differences are also common, and heart defects or developmental delay each occur in about 15% of people.

What a diagnosis changes

Surgical repair of anal and hand differences where needed, hearing assessment, and long-term monitoring of kidney function and heart. Each child of an affected person has a 1 in 2 chance of inheriting the change, so genetic counselling and parental testing are recommended, as features in a parent may be mild.

Genes analysed

Also known as

TBS1; townes-brocks branchiootorenal-like syndrome

MONDO:0054581OMIM 107480MedGen 1635275Sources: [1][2][3]

Why whole genome sequencing

Townes-Brocks syndrome runs in families in a dominant way, so testing relatives can matter even when their signs are mild.

Kidney and hearing checks each year

Kidney function is monitored every year, even when the kidneys look normal at first. Hearing is assessed each year as well, and hearing loss is treated early. Knowing the SALL1 change helps the care team plan these checks from an early age.

A 1 in 2 chance for each child

Each child of an affected person has a 1 in 2 chance of inheriting the change. Because features in a parent can be mild, parental testing can clarify who is at risk. Once the SALL1 change is known in the family, prenatal and preimplantation genetic testing are possible.

References

  1. Graziano C, Olivucci G, 2007. SALL1-Related Townes-Brocks Syndrome. GeneReviews
  2. Townes-Brocks Syndrome. MedlinePlus Genetics
  3. Leduc F, Brunelle P, Escande F, Ramdane N, Bellengier L, Giacomello L et al., 2025. Townes-Brocks syndrome: genotype-phenotype correlations of SALL1 variants in our series and the literature. European journal of human genetics : EJHG

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