What are the other Names for this Condition? (Also known as/Symptoms)

• AR dRTA with Hearing Loss
• Autosomal Recessive Renal Tubular Acidosis with Progressive Nerve Deafness
• Type 1 Renal Tubular Acidosis with Sensorineural Deafness

What is Renal Tubular Acidosis with Deafness? (Definition/Background Information)

• Renal Tubular Acidosis with Deafness is a rare and genetic disorder that is characterized by dysfunction of the kidneys and hearing problems
• It is reported to occur more commonly in regions where children are born to parents who are close relatives (such as first cousins)
• Renal Tubular Acidosis with Deafness is caused by genetic mutations, which results in impaired functioning of the kidneys and ears, due to a defective enzyme
• The major symptoms of Renal Tubular Acidosis with Deafness are nausea, vomiting, dehydration, softening of bones, formation of kidney stones, hearing impairment (known as sensorineural hearing loss, beginning in childhood or young adulthood), and short stature
• For diagnosis of Renal Tubular Acidosis with Deafness, a healthcare professional may use information from clinical findings, urine tests, blood tests and imaging. The disorder is confirmed using genetic tests
• Some complications of Renal Tubular Acidosis with Deafness may include a drop in the potassium levels in blood (hypokalemia) leading to extreme muscle weakness, chronic kidney problems, continued hearing loss, and abnormal heart rhythms
• Oral alkali treatment to combat acidic blood is the main method for combating the condition and reversing the effects of acidosis. Additionally, potassium supplements along with medicines to prevent or treat kidney stones, treatment for hearing loss, and pain medication for bone pain may be required
• Since Renal Tubular Acidosis with Deafness is a genetic condition, there are no available methods or guidelines to prevent it. However, if there is a family history of the disorder, genetic counselling may help the prospective parents understand the probability and risks of their child being born with the disorder
• The prognosis of Renal Tubular Acidosis with Deafness is considered to be excellent with early diagnosis, followed by prompt and continued treatment. Nonetheless, hearing loss might continue to occur in many individuals and eventually deafness may occur. The prognosis also depends upon the severity of the signs and symptoms; individuals with mild signs and symptoms have better prognosis than those with severe signs and symptoms

Who gets Renal Tubular Acidosis with Deafness? (Age and Sex Distribution)

• Renal Tubular Acidosis with Deafness is a rare genetic condition. The exact statistics for the prevalence of the condition are not known
• The condition is manifested at birth and both males and females are at risk
• It is reported that the prevalence is higher in populations where marriages between close relatives (such as cousins) are common

What are the Risk Factors for Renal Tubular Acidosis with Deafness? (Predisposing Factors)

The major risk factors for Renal Tubular Acidosis with Deafness include:

• Being an offspring of parents who are close relatives (first cousins, siblings, and other close relations)
• A family history of Renal Tubular Acidosis with Deafness

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Renal Tubular Acidosis with Deafness? (Etiology)

Mutations in either the ATP6V1B1 or ATP6V0A4 genes are the primary causes of Renal Tubular Acidosis with Deafness.

• These genes code for subunits of an enzyme known as vacouolar H+-ATPase (V-ATPase)
• V-ATPase is present in the functional unit of the kidneys called the nephrons, as well as the inner ear. In its normal form this enzyme helps mobilize hydrogen ions (H+) across membranes and regulates:
  • The amount of acid that is removed from blood to pass into the urine
  • The pH of the inner ear fluid known as the endolymph 
• When the V-ATPase has defective subunits because of gene mutations,
  • The body loses its ability to control the blood pH, and the blood becomes acidic (owing to compromised function of the nephron’s tubules) as a result of acid absorption in the blood. This is also known as metabolic acidosis
  • There is dysregulation of pH of endolymph, causing harm to the inner ear
• Renal Tubular Acidosis with Deafness is inherited in an autosomal recessive manner

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children, born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected). 

What are the Signs and Symptoms of Renal Tubular Acidosis with Deafness?

Some major symptoms of Renal Tubular Acidosis with Deafness include:

• Feeding problems in infants, leading to difficulty for infant to gain weight
• Nausea, vomiting, and dehydration
• Short stature
• Impaired hearing
• Kidney stones
• Softening and weakening of bones, leading to:
  • Pain in bones
  • Bowlegs
  • Difficulty with walking

How is Renal Tubular Acidosis with Deafness Diagnosed?

The diagnosis of Renal Tubular Acidosis with Deafness is made based on the following:

• A thorough physical examination
• An assessment of medical history of family (close and extended)
• An evaluation of symptoms
• Urine tests to check for the following:
  • pH of urine
  • Urinary electrolyte imbalance
  • Kidney function
• Blood tests to detect normal anion gap metabolic acidosis
• Hearing tests (audiometry)
• Imaging studies to check for enlarged vestibular aqueduct (a canal that connects the inner ear to the brain is found to be enlarged in many individuals with the disorder)
• DNA analysis and sequencing of DNA to detect/confirm gene mutations

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Renal Tubular Acidosis with Deafness?

The potential complications of Renal Tubular Acidosis with Deafness include:

• A condition known as ‘hypokalemia’, which is a decrease in blood potassium levels. This condition could lead to hypokalemic paralysis, where an individual experiences extreme muscle weakness
• Aberrant heart rhythms
• Permanent hearing loss
• Fatigue, difficulty in movement due to bone pain
• Nephrocalcinosis, or calcium deposits in kidneys
• Chronic renal failure, in rare cases

How is Renal Tubular Acidosis with Deafness Treated?

Treatment options for Renal Tubular Acidosos with Deafness include:

• Oral alkali replacement (citrate or bicarbonate) balances the acidity, and is reported to overcome effects of the disease in order to allow for normal growth in children
• When hypokalemia is experienced by an individual, potassium salt supplementation may be required
• Correction of skeletal abnormalities
• Medication to prevent or treat kidney stones
• Pain medication, as needed
• Treatment for hearing impairment, since alkali therapy does not address the inner ear problems associated with RTA with Deafness

How can Renal Tubular Acidosis with Deafness be Prevented?

• Currently, there are no specific methods or guidelines to prevent Renal Tubular Acidosis with Deafness since it is a genetic condition
• Genetic testing of the expecting parents (and related family members) followed by prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during child-bearing
• If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Renal Tubular Acidosis with Deafness

For individuals diagnosed with the condition and being treated, regular medical screening at periodic intervals with tests and physical examinations are strongly recommended,

What is the Prognosis of Renal Tubular Acidosis with Deafness? (Outcomes/Resolutions)

• The prognosis of Renal Tubular Acidosis with Deafness is generally excellent with early diagnosis and continual appropriate treatment. Individuals with mild signs and symptoms have better prognosis than those with severe signs and symptoms
• Auditory problems may continue to progress even when alkali therapy is undertaken; hearing loss can be progressive
• Many affected individuals develop kidney stones
• Weakening of the bones and bone pain have been reported by many patients

Additional and Relevant Useful Information for Renal Tubular Acidosis with Deafness:

• Renal tubular dysgenesis (RTD) is another serious kidney disorder that is found in a developing fetus

The following link can help you understand renal tubular dysgenesis:

http://www.dovemed.com/diseases-conditions/renal-tubular-dysgenesis/