Inherited distal RTA typically presents early in life with hyperchloremic metabolic acidosis, failure to thrive, hypercalciuria, and nephrocalcinosis that is usually seen on ultrasound within the first month of life ( Santos et al., 2015). Kelsey Richardson, Karyn Yonekawa, in Avery's Diseases of the Newborn (Tenth Edition), 2018 Distal Renal Tubular Acidosis (Type 1 RTA)ĭistal RTA is caused by an inability of the collecting duct to excrete adequate hydrogen (H +) ions because of poor NH4 + excretion. Their urine citrate is extremely low despite mildly reduced or even normal serum bicarbonate levels. 82 Patients with dRTA fail to lower their urine pH below 5.5 following ingestion of an acid load. One form of dRTA that targets carbonic anhydrase II results in osteopetrosis and brain calcifications. 82 Some are autosomal recessive and can also result in hearing loss others are autosomal dominant. Although there are secondary causes of dRTA such as Sjögren syndrome and use of carbonic anhydrase inhibitors (e.g., acetazolamide), there are also a number of hereditary causes of dRTA. The increased filtered load of calcium and phosphate, along with the elevated urine pH and hypocitraturia, results in favorable conditions for calcium phosphate stone formation. The metabolic acidosis leads to resorption of both calcium and phosphate from bone. 27,28,47,72,81 This inability to adequately acidify the urine results in metabolic acidosis, hypocitraturia, hypokalemia, hypercalciuria, nephrocalcinosis, and stones. Bushinsky, in Williams Textbook of Endocrinology (Thirteenth Edition), 2016 Distal Renal Tubular AcidosisĭRTA is caused by dysfunctional α-intercalated cells, resulting in defective acid excretion. Thus it is type 1 RTA that is most commonly referred to as distal RTA (dRTA).Īnirban Bose. Both types 1 and 4 dRTA actually cover large groups of different conditions, both inherited and acquired. In contrast, type 4 RTA is associated with hypoaldosteronism (true and pseudo-) and defective distal nephron sodium handling by principal cells in this same nephron segment, and therefore with hyperkalemia, and only secondarily with inadequate acid excretion.
In this chapter we are mainly concerned with type 1 RTA, which is directly due to dysfunction of the acid-handling α-intercalated cells (α-IC) in the collecting system, and this distal form is associated with hypokalemia.
Unfortunately, the classification of the RTAs can be confusing, because within the overall historical scheme of nomenclature, types 1 and 4 RTA are both caused by distal nephron dysfunction. Karet, in Genetic Diseases of the Kidney, 2009 Introductionĭistal renal tubular acidosis is a disease of defective urinary acidification, which is caused by insufficient net acid excretion by the kidney.