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Disease Profile

Distal renal tubular acidosis

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

All ages

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ICD-10

N25.8

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Summary

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.
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Orpha Number: 18

Definition
Distal renal tubular acidosis (dRTA) is a disorder of impaired net acid secretion by the distal tubule characterized by hyperchloremic metabolic acidosis. The classic form is often associated with hypokalemia whereas other forms of acquired dRTA may be associated with hypokalemia, hyperkalemia or normokalemia.

Epidemiology
Prevalence of dRTA is unknown but is often underreported. The hereditary forms of dRTA are more prevalent in areas of high consanguinity (Arabic peninsula and North Africa) whereas acquired dRTA has been reported more frequently in Western countries.

Clinical description
Disease onset can occur at any age, depending on cause. Hereditary dRTA subtypes include autosomal dominant (AD) and autosomal recessive (AR) dRTA (see these terms). A recessive subtype of dRTA associated with anemia has also been described in Southeast Asia. AR forms are frequently diagnosed in infants and young children. AD dRTA is mostly diagnosed in adolescents and young adults. Patients with dRTA can be asymptomatic or can present with polyuria, polydipsia, weakness and fatigue (symptoms associated with hypokalemia). Failure to thrive, rickets, stunting of growth (seen in children) and osteomalacia or osteopenia (seen in adults) are a result of urinary calcium wastage and a loss of calcium salts from the bones. Hypercalciuria, nephrolithiasis and nephrocalcinosis usually occur. Low plasma potassium levels in those with the classic form of dRTA can also cause cardiac arrhythmias, paralysis and even death. In the recessive forms of dRTA, progressive and irreversible deafness often occurs.

Etiology
dRTA can be acquired or inherited. AD dRTA is usually due to mutations in the SLC4A1 gene (17q21.31). Mutations in the ATP6V1B1 gene (2p13) or ATP6V0A4 gene (7q34) are responsible for AR dRTA with deafness. AR dRTA without deafness or late onset deafness has been mainly described in patients with mutations in the ATP6V0A4 gene but overlap does exist in that some patients with this mutation develop deafness and others do not. Acquired forms of dRTA are thought to be caused by autoimmune diseases such as Sjögren syndrome (see this term) or secondary to other conditions like sickle cell anemia, systemic lupus erythematosus (see these terms), chronic obstructive uropathy, or post-renal transplantation.

Diagnostic methods
The disease is characterized by hyperchloremic metabolic acidosis. The inability to lower urine pH below 5.5 and a positive urine anion gap during spontaneous metabolic acidosis is indicative of dRTA. Provocative tests for further diagnosis include the NH4Cl acidifying test and the furosemide test. Patients with dRTA also show renal potassium wasting except in the hyperkalemic type of dRTA. Molecular genetic testing for one of the causal genetic mutations can also confirm diagnosis.

Differential diagnosis
The main differential diagnosis is proximal RTA (see this term) along with other causes of chronic metabolic acidosis (i.e. diarrhea).

Antenatal diagnosis
Antenatal diagnosis is rarely performed.

Genetic counseling
The inherited forms of dRTA are inherited autosomal dominantly or recessively and genetic counseling is possible.

Management and treatment
Alkali therapy is the standard treatment (to achieve normal serum bicarbonate levels). Patients are usually given sodium bicarbonate or sodium citrate. Children require very high doses (4-8 meq/kg/day) whereas adults need much lower doses (1-2 meq/kg/day). Potassium replacement is also necessary in hypokalemic patients and potassium citrate is usually recommended. The dose depends on the severity of hypokalemia. Hyperkalemic types require low dietary potassium intake and other therapies.

Prognosis
All forms of dRTA are chronic and may have significant effects on growth and development. With treatment there is no decrease in life expectancy and renal failure is uncommon but progressive chronic kidney disease may sometimes occur if there are recurrent kidney stones and when nephrocalcinosis is very severe.

Visit the Orphanet disease page for more resources.

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.