Autosomal Recessive Distal Renal Tubular Acidosis (dRTA)

Type 1 RTA or distal RTA

This is the most common type of RTA. It occurs when there is a problem at the end or distal part of the kidney tubules, where acid is normally excreted into the urine. In Type 1 RTA, the kidneys are unable to properly secrete hydrogen ions into the urine, leading to an accumulation of acid in the blood.

► Type 1 RTA is often caused by a genetic mutation that affects the function of the distal tubules in the kidneys. In some cases, it can be acquired due to conditions like autoimmune diseases, medications (e.g., lithium), or chronic kidney diseases.­

Type 2 RTA or proximal RTA

Type 2 RTA occurs when the proximal (near) part of the renal tubules fails to properly reabsorb bicarbonate from the urine. As a result, too much bicarbonate is lost in the urine, leading to metabolic acidosis.

► Type 2 RTA can be either genetic or acquired. It is usually associated with inherited disorders like Fanconi syndrome or Dent disease. Acquired causes can include multiple myeloma, Sjögren's syndrome, or the use of certain medications such as carbonic anhydrase inhibitors.

Type 3 RTA

Type 3 RTA is a rare form of the condition and can be associated with other underlying medical conditions or genetic disorders. It may have characteristics of both Type 1 and Type 2 RTA.

Type 4 RTA or hyperkalemic RTA

Type 4 RTA, or hyperkalemic RTA, occurs when the tubules are unable to remove enough potassium, which also interferes with the kidney’s ability to remove acid from the blood.

►Type 4 RTA is primarily caused by an abnormal response to the hormone aldosterone, which regulates sodium and potassium balance in the body. Conditions that affect aldosterone function, such as Addison's disease or certain medications (e.g., nonsteroidal anti-inflammatory drugs or ACE inhibitors), can lead to type 4 RTA.

Signs include low levels of potassium and bicarbonate (a waste product produced by your body) in the blood. The potassium level drops if your kidneys send too much potassium into your urine instead of returning it to the blood. As potassium is involved in the regulation of  nerve and muscle function, low potassium levels can cause

• extreme weakness
• irregular heartbeat
• paralysis 
• death

Signs include high potassium and low bicarbonate levels in the blood. Symptoms of type 4 RTA are

• abdominal pain 
• fatigue that does not go away
• weak muscles
• not feeling hungry
• weight lost

The first step in diagnosing RTA is a thorough clinical assessment with a detailed medical history and recognizing symptoms such as frequent urination, excessive thirst, muscle weakness, bone pain, and growth retardation (in children). Also, physical examination may reveal signs such as dehydration, abnormal growth patterns (in children), or muscle weakness.

In some cases, imaging studies such as renal ultrasound or CT scans may be conducted to assess the kidneys' structure and rule out any anatomical abnormalities or kidney stones that could contribute to RTA. In certain situations, additional specialized tests, like genetic testing, may be required to identify specific genetic mutations associated with certain types of RTA.

Identify and Address Underlying Causes:

RTA can be primary (inherited) or secondary (acquired). Treating any underlying conditions or causes, such as autoimmune diseases, medications, or electrolyte imbalances, is essential. If a medicine is causing the RTA, stopping or changing the dose would be suggested.

Correct Electrolyte Imbalances: 

Depending on the type of RTA, imbalances in electrolytes like potassium, calcium, and sodium may experience. Treatment involves managing these imbalances.

Alkali Therapy:

A Therapy to correct the acid-base imbalance the  alkali therapy in the form of oral sodium bicarbonate (baking soda) or other alkali substances is provided. The dosage and type of alkali used will depend on the specific type of RTA.

Thiazide diuretics:

To reduce calcium excretion and prevent kidney stones.

Diet Modifications:

Depending on the type of RTA and the associated electrolyte imbalances, dietary changes may be necessary.

Monitor Kidney Function:

Regular monitoring of kidney function is essential to assess the effectiveness of treatment and make adjustments as needed.

Supportive Care:

Patients with RTA may require ongoing care and support to manage their condition and maintain their overall health. Regular follow-up appointments with a nephrologist (kidney specialist) are often necessary.