Towards the identification of (a) gene(s) for autosomal dominant medullary cystic kidney disease.
Medullary cystic kidney disease (MCKD) belongs with nephronophthisis (NPH) in a group of inherited tubulo-interstitial nephritis, which has been referred to as the NPH-MCKD complex. Although MCKD and NPH share morphological features, they differ in several respects. The most common variant is recessive juvenile NPH, with onset in childhood and leading to end-stage renal disease (ESRD) within the 2nd decade of life; the most frequent extrarenal involvement is tapeto-retinal degeneration. MCKD is a dominant condition recognized in later life and leading to ESRD at the age of 50 years; hyperuricemia and gout can be associated features. The first sign of MCKD is polyuria; later, the clinical findings relate to renal insufficiency. Originally, NPH and MCKD were considered separate entities. Subsequently, it has been suggested that the two diseases were a single disorder due to the clinico-pathological identity. This unifying conception was later refuted due to the identification of MCKD dominant families. Recently, considerable insight has been gained into the genetics of the NPH-MCKD complex. The majority of juvenile NPH cases are due to deletion of the NPHP1 gene on chromosome 2q13. Genes for infantile and adolescent NPH have been localized respectively to chromosome 9q22-q31 and 3q22. A new locus, NPHP4, has been recently identified on chromosome 1p36. Two genes predisposing to dominant MCKD, MCKD1 and MCKD2, have been localized to chromosome 1q21 and 16p12. Independent confirmation of the locations of MCKD1 and MCKD2 in other MCKD families, with or without hyperuricemia and gout, has been reported. The gene for familial juvenile hyperuricemic nephropathy (FJHN), a phenotype that is very similar to MCKD, was recently mapped to 16p12, in a region overlapping with the MCKD2 locus, raising the question as to whether MCKD2 and FJHN are allelic variants of the same disease entity. The ultimate proof of the allelism between MCKD2 and FJHN will be provided by the identification of the responsible gene(s). Identification and characterization of the MCKD and FJHN genes will help to clarify the pathogenesis and classification of hereditary tubulo-interstitial nephritides.
Scolari
Francesco
F
Division and Chair of Nephrology, Spedali Civili, Brescia, Italy. fscolari@tin.it
Viola
Battista Fabio
BF
Ghiggeri
Gian Marco
GM
Caridi
Gianluca
G
Amoroso
Antonio
A
Rampoldi
Luca
L
Casari
Giorgio
G
D006801:Humans; D007679:Kidney Medulla; D008967:Molecular Biology; D009395:Nephritis, Interstitial / Q000145:classification / Q000235:genetics; D016891:Polycystic Kidney, Autosomal Dominant / Q000145:classification / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology