Inbreeding and nephrolithiasis in Croatian island isolates

The aim of this study was to investigate a recessive genetic component in susceptibility to nephrolithiasis (NL) by comparing its prevalence in highly inbred, moderately inbred and non-inbred villages of three Croatian islands: Brac, Hvar and Korcula. The average inbreeding coefficient of each village population (F) was estimated in a random sample of 20-30% adults from 14 villages using Wright's path method (based on genealogical information), isonymy data and average deviation from Hardy-Weinberg expectations for MN, Ss and Kk serogenetic polymorphisms. The six villages with the greatest genealogical F value (0.025-0.049; current total population N=1,401), the four with intermediate value (0.012-0.015; N=998) and the four with the smallest value (0.002-0.008; N=1,500) were chosen for this study. Medical records of entire populations were reviewed and the diagnosis of NL was established according to unified criteria, based on the information from the specialists in general hospitals and on the agreement in diagnosis between the investigators and local general practitioners. The variance in environmental and socio-cultural factors between villages was shown to be minimal. Prevalence of NL in each village was standardised by sex and age to the total population of all 14 villages. The standardized prevalence of NL was 1.5% in the group of villages with low F, 2.3% in the group with moderate F (p<0.10), and 5.4% in the group with high F (p<0.001). The correlation factor between F values by villages and the standardized prevalence of NL was 0.45 (p<0.05). The study showed that a large number of predominantly recessive genetic factors might mediate the susceptibility to formation of renal stones in humans.