Overview
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RTA is a type of metabolic acidosis that is due to either abnormal bicarbonate loss or acid excretion by the kidneys in presence of a normal or near normal glomerular filtration rate.
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Results in non-anion gap metabolic acidosis.
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Metabolic acidosis not due to gastrointestinal bicarbonate loss or acute/chronic renal insufficiency.
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Related to either proximal tubule dysfunction of bicarbonate reabsorption, failure of distal tubule excretion of acid, or mineralocorticoid deficiency.
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Other findings may include recurrent nephrocalcinosis, growth retardation, and osteomalacia/rickets in children.
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Can be either inherited, transient, or acquired.
Etiology
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Distal RTA (type 1) is due to defective distal tubular H + secretion.
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Clinical features include impairment of growth, polyuria, hypercalciuria, lithiasis, nephrocalcinosis, and K + depletion.
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Acquired forms related to hypergammaglobulinemia, autoimmune disorders such as SLE or Sjögren syndrome, and pts with chronic liver disease.
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Can be associated with sensorineural hearing loss.
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Proximal RTA (type 2) is due to defective proximal tubule reabsorption of bicarbonate.
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Manifests as stunted growth in children.
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Can be associated with Fanconi syndrome, and if so, can manifest with osteomalacia and rickets.
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Other causes include medications and toxins such as acetazolamide, aminoglycoside antibiotics, expired tetracyclines, lead, cadmium, and mercury.
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Type 3 RTA is a combination of types 1 and 2.
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Can be transient in pediatric pts with type 1 RTA.
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Carbonic anhydrase II deficiency is an AutoR syndrome associated with osteoporosis, RTA, cerebral calcification, and mental retardation.
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Hyperkalemic RTA (type 4): Due to either mineralocorticoid deficiency or hormone resistance
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Most frequently observed in children with hypo- or pseudohypoaldosteronism
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Also found to be related with diabetic nephropathy, SLE, and AIDS nephropathy
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Drug induced causes include COX inhibitors, ACE-I’s, heparin, K retaining diuretics, trimethoprim, and others
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