Kidney biopsy may be indicated in patients for whom a genetic diagnosis cannot be established or in those with a substantial reduction in eGFR (i.e. to <30 ml/min/1.73 m2) for whom a biopsy sample could be informative in establishing a rare diagnosis (such as congenital membranous nephropathy due to anti-neutral endopeptidase (NEP) antibodies or other glomerulopathies) and in estimating prognosis. The gene discussed is MME; the disease is glomerular disorder.