Clinical Features of Townes-Brocks Syndrome

 

Acronym: REAR (renal, ear, anal, radial)

 

Inheritance: autosomal dominant with variable expression

 

Genetic locus: 16q12.1, with mutation of SALL1; a deletion at the locus may affect distal genes (SLC6A2, GNAO1, MT3)

 

Ear and hearing defects:

(1) sensorineural hearing loss

(2) anomalies of the external ear (small, overfolded superior helix, "satyr", protruding)

(3) preauricular tags or pits

 

Thumb and digit defects:

(1) triphalangeal thumb

(2) bifid thumb

(3) preaxial polydactyly

(4) broadening of distal phalanx of thumb

(5) ulnar deviation of the distal phalanx in the thumb

(6) overlapping toes

(7) fifth toe clinodactyly

(8) hypoplastic third toe

(9) anomalies of metacarpal bones

(10) syndactyly of fingers or toes

 

Anorectal defects:

(1) imperforate

(2) anterior displacement

(3) stenosis

(4) rectal fistulas (rectoperineal, rectovaginal, etc)

(5) excess perianal skin

 

Renal and genital defects:

(1) unilateral or bilateral renal hypoplasia or aplasia

(2) renal dysplasia

(3) multicystic kidney disease

(4) renal failure

(5) urethral valves

(6) vesicoureteral reflux

(7) meatal stenosis

(8) bifid scrotum

(9) midline perineal raphe

(10) hypospadias

 

Other defects:

(1) cardiac anomalies

(2) developmental delay which may be related to hearing loss

(3) eye defects

(4) hemifacial microsomia

 

Mental retardation is not a typical finding.

 

Findings not typically seen in TBS (should prompt a search for another diagnosis):

(1) hypoplasia of the thumb

(2) radial bone abnormalities

(3) vertebral anomalies

(4) tracheo-esophageal fistula

(5) craniosynostosis

 

Differential diagnosis:

(1) VATER

(2) Fanconi anemia

(3) oculauriculovertebral spectrum

(4) cat eye syndrome

(5) Baller-Gerold syndrome