Figure 626

A and B, Potential defects and causes of proximal renal tubular acidosis (RTA) (type 2). Excluding the case of carbonic anhydrase inhibitors, the nature of the acidification defect responsible for bicarbonate (HCO3) wastage remains unknown. It might represent defects in the luminal sodium ion- hydrogen ion (Na+-H+) exchanger, basolateral Na+-3HCO^ cotransporter, or carbonic anhydrase activity. Most patients with proximal RTA have additional defects in proximal tubule function (Fanconi's syndrome); this generalized proximal tubule dysfunction might reflect a defect in the basolateral Na+-K+ adenosine triphosphatase. K+—potassium ion; CA—carbonic anhydrase. Causes of proximal renal tubular acidosis (RTA) (type 2). An idiopathic form and cystinosis are the most common causes of proximal RTA in children. In adults, multiple myeloma and carbonic anhydrase inhibitors (eg, acetazo-lamide) are the major causes. Ifosfamide is an increasingly common cause of the disorder in both age groups.

Selective defect (isolated bicarbonate wasting)

Dysproteinemic states

Primary (no obvious associated disease)

Multiple myeloma

Genetically transmitted

Monoclonal gammopathy

Transient (infants)

Drug- or toxin-induced

Due to altered carbonic anhydrase activity

Outdated tetracycline

Acetazolamide

3-Methylchromone

Sulfanilamide

Streptozotocin

Mafenide acetate

Lead

Genetically transmitted

Mercury

Idiopathic

Arginine

Osteopetrosis with carbonic

Valproic acid

anhydrase II deficiency

Gentamicin Ifosfamide

York-Yendt syndrome

Generalized defect (associated with multiple dysfunctions of the proximal tubule)

Tubulointerstitial diseases

Primary (no obvious associated disease)

Renal transplantation

Sporadic

Sjögrens syndrome

Genetically transmitted

Medullary cystic disease

Genetically transmitted systemic disease

Other renal diseases

Tyrosinemia

Nephrotic syndrome

Wilson's disease

Amyloidosis

Lowe syndrome

Miscellaneous

Hereditary fructose intolerance (during

Paroxysmal

administration of fructose)

nocturnal hemoglobinuria

Cystinosis

Hyperparathyroidism

Pyruvate carboxylate deficiency

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