Leaky tubules, shedding bicarbonate plus other things, leading to acidosis.

• Type 1 is distal tubule, which does most of the reabsorbing.
• Type 2 is proximal tubule, so similar but less severe.
• Type 3 probably just a mixture of types 1 and 2!
• Type 4 have high rather than low potassium, so clearly not a leakage issue. Related to aldosterone ineffectiveness.

Types 1 and 2 can present with growth failure, else the effects of hypokalaemia (profound muscle weakness) and acidosis (abdominal pain). Type 1 leads to progressive kidney disease, with the associated bone disease (rickets). May also end up with stones. Associated with sickle cell, Ehlers Danlos.

Type 2 usually Fanconi syndrome so leakage of amino acids, phosphate etc. Can be caused by Cystinosis, Wilson’s, hereditary fructose intolerance, poisoning.

Type 4 often related to drugs, but also Addison’s, urinary tract obstruction.