Primary hyperoxaluria is a rare condition (autosomal recessive), resulting in increased excretion of oxalate (up to 600mg a day from normal 50mg a day), with oxalate stones being common. Signs/symptoms Pathophysiology The buildup of oxalate in the body causes increased renal excretion of oxalate (hyperoxaluria), which in turn results in renal and bladder stones. [Source: Wikipedia ]