Karyomegalic interstitial nephritis (KMIN; OMIM 814617, ORPHA 401996) is a very rare autosomal recessive inherited systemic disease caused by germline pathogenic variants in the FAN1 gene, which encodes the FANCD2/FANCI-associated nuclease 1.1 The gene discussed is FANCD2; the disease is karyomegalic interstitial nephritis.