Family distances can reveal hidden consanguinity

Family distances, defined as summary measures of all possible geographic distances between birthplaces of paternal ancestors and birthplaces of maternal ancestors in a given generation, were compared in patients with autosomal recessive disorders and patients with Down's syndrome. In general, family distances in Down's syndrome patients were twice the family distances in patients with autosomal recessive disorders, even after the exclusion of rare disorders or cases with overt consanguinity. In modern, Western European societies grandparental and great-grandparental family distances may be more appropriate measures of the effect of population structure than parental distance or parental consanguinity.