Townes-Brocks syndrome

Townes-Brocks syndrome (TBS) is a rare genetic disease that affects fewer than 200 people in the entire world.^[1] It affects both males and females equally.^[2] The condition was first identified in 1972.^[2]

Additional recommended knowledge

What is the Correct Way to Check Repeatability in Balances?

Daily Sensitivity Test

Essential Laboratory Skills Guide

Symptoms

TBS sufferers may have the following symptoms:^[3]

• Abnormalities of the external ears (unusually large or small, unusually shaped, sometimes with sensorineural hearing loss or deafness due to lesions or dysfunctions of part of the internal ear or its nerve tracts and centers or conductive hearing loss from the external or middle ear), dysplastic ears, lop ear (over-folded ear helix), preauricular tags or pits (a rudimentary tag of ear tissue typically located just in front of the ear).

• Anorectal abnormalities, i.e. malformations of the anus, including imperforate anus/absence of an anal opening, rectovaginal fistula, anal stenosis, unusually placed anus.

• Renal abnormalities, sometimes leading to impaired renal function or renal failure, including hypoplastic kidneys (underdeveloped), multicystic kidneys, dyspastic kidneys.

• Heart abnormalities, including tetralogy of fallot and defects of the ventricular septum.

• Hand and foot abnormalities, such as hypoplastic thumbs, fingerlike thumbs, syndactyly (webbed fingers/toes), fusion of the wrist bones, overlapping foot and/or toe bones.

Learning difficulties have been reported in some children with TBS. For others, intelligence is within the normal range.

These abnormalities, which are present prenatally, can range from minor to severe, and as with similar disorders, most individuals with this condition have some, but not all, of these traits.

Causes

TBS is an autosomal dominant multiple malformation disorder involving the a mutation of the gene SALL1, which encodes a transcriptional repressor which interacts with TRF1/PIN2 and localizes to pericentromeric heterochromatin. The clinical features of TBS overlap with VATER and VACTERL associations, oculo-auriculo-vertebral (OAV) spectrum, branchio-oto-renal (BOR) syndrome, and Fanconi anemia and other 'anus-hand-ear' syndromes.^[4]

Although some symptoms can be life-threatening, many people diagnosed with Townes-Brocks Syndrome live a normal lifespan.^[2]

Notes

1. ^ Faces of Children
2. ^ ^{a b c} Contact a Family
3. ^ National Organization for Rare Diseases
4. ^ GeneDX