Figure 627

A and B, Potential defects and causes of classic distal renal tubular acidosis (RTA) (type 1). Potential cellular defects underlying classic distal RTA include a faulty luminal hydrogen ion-adenosine triphosphatase (H+ pump failure or secretory defect), an abnormality in the basolateral bicarbonate ion-chloride ion exchanger, inadequacy of carbonic anhydrase activity, or an increase in the luminal membrane permeability for hydrogen ions (backleak of protons or permeability defect). Most of the causes of classic distal RTA likely reflect a secretory defect, whereas amphotericin B is the only established cause of a permeability defect. The hereditary form is the most common cause of this disorder in children. Major causes in adults include autoimmune disorders (eg, Sjogren's syndrome) and hypercalciuria [19]. CA—carbonic anhydrase.

Primary (no obvious associated disease) Sporadic

Genetically transmitted

Autoimmune disorders Hypergammaglobulinemia Hyperglobulinemic purpura Cryoglobulinemia Familial

Sjögrens syndrome Thyroiditis Pulmonary fibrosis Chronic active hepatitis Primary biliary cirrhosis Systemic lupus erythematosus Vasculitis

Genetically transmitted systemic disease Ehlers-Danlos syndrome Hereditary elliptocytosis Sickle cell anemia Marfan syndrome Carbonic anhydrase I deficiency or alteration Osteopetrosis with carbonic anhydrase II deficiency Medullary cystic disease Neuroaxonal dystrophy

Disorders associated with nephrocalcinosis Primary or familial hyperparathyroidism Vitamin D intoxication Milk-alkali syndrome Hyperthyroidism Idiopathic hypercalciuria Genetically transmitted Sporadic Hereditary fructose intolerance

(after chronic fructose ingestion) Medullary sponge kidney Fabry's disease Wilson's disease

Drug- or toxin-induced Amphotericin B Toluene Analgesics Lithium Cyclamate Balkan nephropathy Tubulointerstitial diseases Chronic pyelonephritis Obstructive uropathy Renal transplantation Leprosy Hyperoxaluria

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