Introduction:
Townes-Brocks syndrome is a rare genetic disorder that consists of a triad of symptoms like obstruction in the anal opening, structural defects in ears causing hearing loss, and malformed thumbs like the presence of an extra thumb or small thumb. Other organs involved in these disorders are the kidney, heart, brain, and genital areas. People affected by Townes - Brocks syndrome present at least two main features of the triad along with the other symptoms. Townes-Brocks syndrome is referred to as renal-ear-anal-radial (REAR) syndrome.
What Is the Prevalence of Townes-Brocks Syndrome?
The exact prevalence of Townes-Brocks syndrome is unknown, but it is estimated to be present in one in 250,000 people in the general population.
What Are the Causes of Townes-Brocks Syndrome?
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Townes - Brocks syndrome is supposed to be caused by a genetic mutation of the SALL1 (spalt-like transcription factor 1) protein and DACT1 (disheveled binding antagonist of beta-Catenin 1) gene on chromosome 14q23.
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Almost 50 percent of cases are due to hereditary causes (runs in the family).
What Are the Signs and Symptoms Associated With Townes-Brocks Syndrome?
Signs and symptoms related to Townes-Brocks syndrome are:
How Can We Diagnose Townes-Brocks Syndrome?
Diagnostic criteria for Townes-Brocks syndrome are:
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Based on Clinical Symptoms: Confirmatory diagnosis of Townes-Brock syndrome is considered only when it involves at least two major clinical symptoms of the triad, along with the presence of some other associated symptoms.
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Single Gene Testing: Genetic evaluation for detecting the presence of SALL1 gene alteration helps in confirming the diagnosis.
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Multigene Panel Test: Along with the SALL1 gene, other gene mutations are also noted, like the DACT1 (disheveled binding antagonist of beta-catenin 1) gene.
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Other Comprehensive Genome Test: Other molecular genome tests like DNA (deoxyribonucleic acid) sequencing and mitochondrial sequencing are done if a single gene and multigene panel test fail to diagnose the condition.
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Auditory Brainstem Response Test (Hearing Test): If the genetic test confirms the diagnosis of Townes syndrome, an immediate hearing test is done to evaluate if any hearing impairment is present.
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Kidney Ultrasound: An ultrasound of the kidney is done to detect any kidney disorders like cysts in the kidney and abnormal shape or size of kidneys.
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Eye Examination: It is done by an ophthalmologist (eye specialist) to check for any abnormalities in the eyes, like clouding of the eye lens or vision disturbances.
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Echocardiogram (ECG): It is done by a cardiologist (heart specialist) to evaluate for any defects in the heart, like ventricular (chamber of the heart) defects.
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Computed Tomography (CT) Scans: These scans are performed on the temporal bone (lateral part of the skull) to detect the structural defects of the ears, like stenosis (narrowing) of the external ear canals.
What Is the Treatment of Townes-Brocks Syndrome?
Management of Townes-brocks syndrome needs a multidisciplinary approach (need various specialties and doctors). Different treatment modalities based on the symptoms diagnosed are:
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Treatment of Hearing Loss: Management of hearing loss is done by using different hearing aids like hearing headbands (given in the first months of life) and bone-anchored hearing devices (given in the early age of life till five years) until the child reaches seven years of age (surgical treatment is done after seven years of age). Cochlear implants (artificial hearing devices) are surgically implanted (placed) in the bones of the inner ear after the age of seven years for a clear and sound hearing.
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Anal Surgery: Surgical treatment is done to treat the obstruction in the anal opening.
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Treatment of Kidney Disorders: Kidney functions should be monitored completely even if there are no symptoms related to the kidney, as some patients develop the symptoms in later stages. If required, hemodialysis (purifying of body blood if a kidney is not functioning) and kidney transplantation are done if the kidney is not functioning properly. Drugs toxic to kidneys are avoided after surgery.
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Heart Surgery: Inborn heart defects are treated surgically by a cardiologist (heart specialist).
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Treatment of Malformed Fingers and Toes: Structural defects of thumbs and toes, like the presence of an extra thumb, are treated surgically by removing extra thumbs, and treatment of overlapping toe bones is also done.
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Genetic Counseling: Genetic counseling of the affected person is done to explain the risk factors to the offspring or reproduction options, and the availability of prenatal testing should be done before pregnancy to avoid risk.
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Prenatal Tests (Test Before Childbirth): Prenatal testing is done in patients if any of their family members have been identified by the SALL1 gene. This test identifies if the child has inherited the SALL1 gene or not. This test cannot predict the severity of the clinical symptoms that can occur after birth.
Conclusion:
Townes syndrome is a rare genetic disorder comprising a triad of symptoms like obstructed anal opening, and structural defects of the ears and the thumbs, along with other minor symptoms affecting kidneys, heart, brain, lower limbs, and eyes in some cases. Most affected people have two major symptoms of the triad, which confirms the presence of Townes-brocks syndrome. As soon as the diagnosis of Townes-brocks syndrome is confirmed, treatment should be started by a multidisciplinary (doctors specializing in different fields) team approach to treat all the underlying symptoms associated with the syndrome. Although there are multiple genetic tests available for diagnosing Townes syndrome, further research is still needed in this area for the early detection and treatment of Townes-brocks syndrome for a better outcome.
