Type 4 RTA is not actually a tubular disorder at all nor does it have a clinical syndrome similar to the other types of RTA described above. It was included in the classification of renal tubular acidoses as it is associated with a mild (normal anion gap) metabolic acidosis due to a "physiological" reduction in proximal tubular ammonium excretion (impaired ammoniagenesis), which is secondary to hypoaldosteronism, and results in a decrease in urine buffering capacity. Its cardinal feature is hyperkalemia, and measured urinary acidification is normal, hence it is often called hyperkalemic RTA or tubular hyperkalemia.

Causes include:

- Aldosterone deficiency (hypoaldosteronism): Primary vs. hyporeninemic (including diabetic nephropathy)

- Aldosterone resistance

1. Drugs: NSAIDs, ACE inhibitors and ARBs, Eplerenone, Spironolactone, Trimethoprim, Pentamidine

2. Pseudohypoaldosteronism

In some patients, RTA shares features of both dRTA and pRTA. This rare pattern was observed in the 1960s and 1970s as a transient phenomenon in infants and children with dRTA (possibly in relation with some exogenous factor such as high salt intake) and is no longer observed. This form of RTA has also been referred to as juvenile RTA.

Combined dRTA and pRTA is also observed as the result of inherited carbonic anhydrase II deficiency. Mutations in the gene encoding this enzyme give rise to an autosomal recessive syndrome of osteopetrosis, renal tubular acidosis, cerebral calcification, and mental retardation. It is very rare and cases from all over the world have been reported, of which about 70% are from the Magreb region of North Africa, possibly due to the high prevalence of consanguinity there.

The kidney problems are treated as described above. There is no treatment for the osteopetrosis or cerebral calcification.

Type 3 is rarely discussed. Most comparisons of RTA are limited to a comparison of types 1, 2, and 4.

Pseudohypoaldosteronism (PHA) is a condition that mimics hypoaldosteronism. However, the condition is due to a failure of "response" to aldosterone, and levels of aldosterone are actually elevated, due to a lack of feedback inhibition.

This syndrome was first described by Cheek and Perry in 1958. Later pediatric endocrinologist Aaron Hanukoglu reported that there are two independent forms of PHA with different inheritance patterns: Renal form with autosomal dominant inheritance exhibiting salt loss mainly from the kidneys, and multi-system form with autosomal recessive form exhibiting salt loss from kidney, lung, and sweat and salivary glands.

Treatment of severe forms of PHA requires relatively large amounts of sodium chloride.

These conditions also involve hyperkalemia.

Types include:

The symptoms of an elevated potassium level are nonspecific, and generally include malaise, palpitations, and muscle weakness. Hyperventilation may indicate a compensatory response to metabolic acidosis, which is one of the possible causes of hyperkalemia. Often, however, the problem is detected during screening blood tests for a medical disorder, or after hospitalization for complications such as cardiac arrhythmia or sudden cardiac death. High levels of potassium (> 5.5 mmol/L) have been associated with cardiovascular events.

Physicians taking a medical history may focus on kidney disease, medication use (e.g. potassium-sparing diuretics), which are common causes.

Hyperkalemia, also spelled hyperkalaemia, is an elevated level of potassium (K) in the blood serum. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels above 5.5 mmol/L defined as hyperkalemia. Typically this results in no symptoms. Occasionally when severe it results in palpitations, muscle pain, muscle weakness, or numbness. An abnormal heart rate can occur which can result in cardiac arrest and death.

Common causes include kidney failure, hypoaldosteronism, and rhabdomyolysis. A number of medications can also cause high blood potassium including spironolactone, NSAIDs, and angiotensin converting enzyme inhibitors. The severity is divided into mild (5.5-5.9 mmol/L), moderate (6.0-6.4 mmol/L), and severe (>6.5 mmol/L). High levels can also be detected on an electrocardiogram (ECG). Pseudohyperkalemia, due to breakdown of cells during or after taking the blood sample, should be ruled out.

Initial treatment in those with ECG changes is calcium gluconate. Medications that might worsen the condition should be stopped and a low potassium diet should be recommended. Other medications used include dextrose with insulin, salbutamol, and sodium bicarbonate. Measures to remove potassium from the body include furosemide, polystyrene sulfonate, and hemodialysis. Hemodialysis is the most effective method. The use of polystyrene sulfonate, while common, is poorly supported by evidence.

Hyperkalemia is rare among those who are otherwise healthy. Among those who are in hospital, rates are between 1% and 2.5%. It increases the overall risk of death by at least ten times. The word "hyperkalemia" is from "hyper-" meaning high; "kalium" meaning potassium; and "-emia", meaning "in the blood".