In order to estimate the recurrence risk to sibs of a previously diagnosed patient with early manifesting ADPKD, we found that 15 out of a total of 65 sibs of the 64 index patients (45% of the theoretically expected 32.5 gene carriers) showed comparable early manifestation. Another 10 symptom free children were diagnosed sonographically as having ADPKD before the age of 18 years, so that the total number of affected sibs was 25/65 in the study group, representing 76% of the gene carriers. Although the gene in childhood manifesting ADPKD can be transmitted through both sexes, a statistically significant (p < 0.05) maternal predominance was observed (M:F = 23:41). In affected sibs ages of onset, initial presentation, and the development of complications appeared to be similar in the majority of families.

Our data indicate a high recurrence risk to sibs for early manifestation of ADPKD which has important implications for genetic counselling and clinical care of affected families and gives clues to the underlying genetic mechanism of childhood onset ADPKD.