Type 2 Proximal Renal Tubular Acidosis (RTA)
Etiology
Genetic Disease
Carbonic Anhydrase II Deficiency Cystinosis Galactosemia Hereditary Fructose Intolerance Glycogen Storage Disease Type I Lowe Syndrome Metachromatic Leukodystrophy Methylmalonic Acidemia Proximal Tubule Cell Sodium Bicarbonate Co-Transporter (NBCe1) Defect Pyruvate Carboxylase Deficiency Tyrosinemia Wilson Disease (see Wilson Disease ): produces both distal and proximal RTA
Renal Interstitial Disease
Balkan Nephropathy Medullary Cystic Disease : produces both distal and proximal RTARenal Transplant Rejection (see Renal Transplant )Sjogren’s Syndrome (see Sjogren’s Syndrome )
Carbonic Anhydrase-Related Conditions
Acetazolamide (Diamox) (see Acetazolamide )Physiology Carbonic Anhydrase Inhibition, Resulting in Bicarbonate Loss in the Urine Carbonic Anhydrase II Deficiency/Osteopetrosis Dichlorphenamide (Keveyis) (see Dichlorphenamide )Physiology Carbonic Anhydrase Inhibition, Resulting in Bicarbonate Loss in the Urine Mafenide Acetate (Sulfamylon) (see Mafenide Acetate )Mechanism Topical sulfonamide antibiotic (which is rapidly absorbed systemically in burn patients) with carbonic anhydrase inhibitor properties -> bicarbonate loss in urine Sulfanilamide Topiramate (Topamax) (see Topiramate )Mechanism Carbonic Anhydrase Inhibition, Resulting in Bicarbonate Loss in the Urine
Physiology
Proximal Convoluted Tubule is the Main Site of Bicarbonate Reabsorption In proximal RTA, proximal tubular bicarbonate absorption is impaired, resulting in renal bicarbonate loss: bicarbonate is replaced by chloride (producing hyperchloremia) Diagnosis
Serum Chemistry
Urine Anion Gap
Urine AG: (urine Na+ + urine K+) – (urine Cl-) Normal: -20 to -50 mEq/L Negative: due to intact renal ammonium ion (NH4+) excretion, as NH4Cl Fractional Excretion of Bicarbonate : >15%Clinical Manifestations
Renal Manifestations
Treatment
Typical Requirement : 10-15 mEq/kg/day (less if thiazide is also used)References
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