Homozygous and compound heterozygous pathogenic variants in FAN1 manifest themselves clinically with a slowly progressive chronic kidney disease [1,2,3,4] and morphologically with karyomegalic interstitial nephritis (KIN; OMIM:614817), which is characterized by grossly shrunken kidneys, and interstitial fibrosis, tubular atrophy and bizarrely enlarged nuclei in tubular epithelial cells histologically [5]. Here, FAN1 is linked to karyomegalic interstitial nephritis.