Nephronophthisis in Finland: epidemiology and comparison of genetically classified subgroups

Nephronophthisis - medullary cystic kidney disease is a progressive chronic tubulointerstitial nephritis leading to terminal renal failure. About two thirds of the patients with familial juvenile nephronophthisis, an autosoma l recessive disease, have a homozygous deletion at the gene locus on 2q13, Through a nationwide search, 59 patients were ascertained in Finland, The i ncidence was 1:61 800 live births when calculated over a 20-year period, of the patients, 17 came from four families showing dominant inheritance and 37 patients from 28 apparently recessive families when classified by family history, clinical features or presence of a deletion on 2q13, Two were con sidered as new dominant mutations; three sporadic patients could not be cla ssified. The most significant difference between the patients with deletion s, patients without deletions but having recessive family history, and pati ents belonging to families with dominant inheritance was the age at first s ymptoms, at the start of dialysis and at transplantation. These facts will be of help in determining the mode of inheritance of a sporadic patient wit hout a deletion.