Kidney Res Clin Pract.  2019 Sep;38(3):267-281. 10.23876/j.krcp.19.056.

Proximal renal tubular acidosis with and without Fanconi syndrome

• Kashoor I
• Batlle D

• KMID: 2457719
• DOI: http://doi.org/10.23876/j.krcp.19.056

Abstract

Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO₃⁻) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO₃⁻ wastage. In a normal kidney, the thick ascending limb of Henle's loop and more distal nephron segments reclaim all of the HCO₃⁻ not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO₃⁻ reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO₃⁻, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaPₐ-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.

Keyword

Acidosis; renal tubular; Drug-induced nephrotoxicity; Fanconi syndrome; Proximal tubular toxicity

MeSH Terms

Acidosis
Acidosis, Renal Tubular*
Amino Acids
Cystinosis
Extremities
Fanconi Syndrome*
Glucose
Kidney
Nephrons
Sodium-Phosphate Cotransporter Proteins
Uric Acid
Amino Acids
Glucose
Sodium-Phosphate Cotransporter Proteins
Uric Acid