Reference Work Entry

Encyclopedia of Molecular Mechanisms of Disease

pp 2092-2094

Townes-Brocks Syndrome

  • Jürgen KohlhaseAffiliated withCenter for Human Genetics


Renal-ear-anal-radial syndrome; TBS

Definition and Characteristics

Townes-Brocks syndrome (TBS) is characterized by the triad of imperforate anus, dysplastic ears (frequently associated with sensorineural and/or conductive hearing impairment), and thumb malformations (triphalangeal thumbs, duplication of the thumb (preaxial polydactyly), and rarely hypoplasia of the thumbs). Renal impairment, including end stage renal disease (ESRD), may occur with or without structural abnormalities (mild malrotation, ectopia, horseshoe kidney, renal hypoplasia, polycystic kidneys, vesico-utereral reflux). Congenital heart disease occurs in 25%. Foot malformations (flat feet, overlapping toes) are common. Mental retardation has been reported in less than 10% of cases. Rare features include iris coloboma, Duane anomaly, Arnold–Chiari malformation type 1, growth retardation, uterine malformations, and hypospadias.


Townes-Brocks syndrome (TBS ...

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