For example, differential methylation of membranous nephropathy cases compared to healthy controls, significant hypermethylation and under expression of mucin-like protocadherin (MUPCDH) between ADPKD kidney tissue and non-ADPKD kidney tissue, differentially methylated regions in congenital renal agenesis, and significantly higher DNA methylation in genes FCRL4, PTPRN2 and IL1RAPL1 of IgAN patients compared to healthy controls; all of which highlight DNA methylation as a potential novel biomarker of rare renal disease. This evidence concerns the gene PTPRN2 and autosomal dominant polycystic kidney disease.