Proximal renal tubular acidosis is a condition that occurs when the kidneys don't properly remove acids in the urine, leaving the blood too acidic.

Your kidneys help regulate your body's acid-base balance (pH). Acidic substances in the body are buffered (counteracted) by alkaline substances, primarily bicarbonate.

The kidneys contain more than a million filtering units, called nephrons. Bicarbonate is reabsorbed into the blood in the initial (proximal) part of the tubule of each nephron. Proximal renal tubular acidosis (Type II RTA) occurs when bicarbonate is not properly reabsorbed by the proximal tubules, leaving the body in an acidic state (called acidosis).

Type II RTA is less common than Type I RTA. It most often occurs during infancy, and may go away by itself.

Causes of type II RTA include:

• Cystinosis
• Drugs such as ifosfamide (a chemotherapy drug), outdated tetracycline, aminoglycoside antibiotics, or acetazolamide
• Fanconi Syndrome
• Inherited fructose intolerance
• Multiple myeloma
• Primary hyperparathyroidism
• Sjogren syndrome
• Wilson's disease