GRHPR and primary hyperoxaluria: Primary hyperoxalurias type 2 (OMIM 260000) and type 3 (OMIM 613616) are respectively caused by a deficiency of glyoxylate reductase-hydroxypyruvate reductase (GRHPR) and 4-hydroxy-2-oxo-glutarate aldolase (HOGA) and each account for approximately 10 % of all primary hyperoxalurias [5, 18].