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, [[Wilson Disease]]): produces both distal and proximal RTA

Renal Interstitial Disease

  • Balkan Nephropathy
  • Medullary Cystic Disease: produces both distal and proximal RTA
  • Renal Transplant Rejection (see Renal Transplant, [[Renal Transplant]])
  • Sjogren’s Syndrome (see Sjogren’s Syndrome, [[Sjogrens Syndrome]])

Carbonic Anhydrase-Related Conditions

  • Acetazolamide (Diamox) (see Acetazolamide, [[Acetazolamide]])
    • Physiology: carbonic anhydrase inhibition -> bicarbonate loss in urine
  • Carbonic Anhydrase II Deficiency/Osteopetrosis
  • Dichlorphenamide (Keveyis) (see Dichlorphenamide, [[Dichlorphenamide]])
    • Physiology: carbonic anhydrase inhibition -> bicarbonate loss in urine
  • Mafenide Acetate (Sulfamylon) (see Mafenide Acetate, [[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, [[Topiramate]])
    • Mechanism: carbonic anhydrase inhibitor properties -> bicarbonate loss in urine

Dysproteinemias

Drugs/Toxins

  • Cadmium (see Cadmium, [[Cadmium]])
  • Copper (see Copper, [[Copper]])
  • Gentamicin (see Gentamicin, [[Gentamicin]])
  • Ifosfamide (Ifex) (see Ifosfamide, [[Ifosfamide]]): produces both distal and proximal RTA
  • L-Arginine
  • Lead (see Lead, [[Lead]])
  • Mercury (see Mercury, [[Mercury]])
  • Outdated Tetracycline (see Tetracycline, [[Tetracycline]])
  • Streptozotocin (see Streptozotocin, [[Streptozotocin]])
  • Tenofovir (Viread) (see Tenofovir, [[Tenofovir]])
  • Uranium (see Uranium, [[Uranium]])
  • Valproic Acid (see Valproic Acid, [[Valproic Acid]])

Other


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

  • Serum Potassium: normokalemia-hypokalemia

Urinalysis (see Urinalysis, [[Urinalysis]])

  • Urine pH: <5.4

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

Sodium Bicarbonate (see Sodium Bicarbonate, [[Sodium Bicarbonate]])

  • Typical Requirement: 10-15 mEq/kg/day (less if thiazide is also used)

Thiazide Diuretic (see Hydrochlorothiazide, [[Hydrochlorothiazide]])

  • May Also Be Useful

References

  • xxx