Primary hyperoxaluria types 1, 2 and 3 are caused by pathogenic variants in AGXT, GRHPR or HOGA1. Secondary hyperoxaluria can be due either to increased intake of oxalate or oxalate precursor(s), or fat malabsorption, or decreased intestinal oxalate degradation. The gene discussed is AGXT; the disease is primary hyperoxaluria type 1.