The kidneys have a central role in the control of acid-base homeostasis owing to bicarbonate reabsorption and production of ammonia and ammonium in the proximal tubule and active acid secretion along the collecting duct. Impaired acid excretion by the collecting duct system causes distal renal tubular acidosis (dRTA), which is characterized by the failure to acidify urine below pH 5.5. This defect originates from reduced function of acid-secretory type A intercalated cells. Inherited forms of dRTA are caused by variants in SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, WDR72 and likely in other genes that are yet to be discovered. Inheritance of dRTA follows autosomal dominant and recessive patterns. Acquired forms of dRTA are caused by various types of autoimmune diseases or adverse effects of some drugs.Incomplete dRTA is frequently found in patients with and without kidney stone disease.These patients fail to appropriately acidify their urine when challenged, suggesting that incomplete dRTA may represent an intermediate state in the spectrum of the ability to excrete acids. Unrecognized or insufficiently treated dRTA can cause rickets and failure to thrive in children, osteomalacia in adults, nephrolithiasis and nephrocalcinosis. Electrolyte disorders are also often present and poorly controlled dRTA can increase the risk of developing chronic kidney disease.
GlossaryEndolymph: Potassium rich fluid filling the cochlear duct and membranous labyrinth of the inner ear, secreted by the stria vascularis.Ovalocytosis: red blood cell deformity with oval-shaped red blood cells, also called elliptcytosis, that are mostly caused by defects in the cytoskeleton. In the case of SAO, the anchoring of the cytoskeleton to the membrane is reduced due to the absence of the AE1 containing protein complex.Sjögren overlap syndrome. Overlap of autoimmune disorders with anti-SSA(Ro) positive antibodies that may include features of Sjögren, SLE, myositis, scleroderma, vasculitis and rheumatoid arthritis.
