Familial occurrence of azoospermia and extreme oligozoospermia

To determine the familial incidence of azoospermia and extreme oligozoospermia (AEO; sperm counts less than 3.10(6)/ml) 147 men with primary AEO were asked, by means of mailed questionnaires, for the occurrence of infertility among their brothers. 119 questionnaires were completed (81%). Out of a total of 163 informative brothers 7 were reported infertile, of whom 3 had a documented AEO. This incidence is probably about double the general population frequency. A familial case of congenital aplasia of the vasa deferentia was found; this has previously been reported to recur in a sibship and may represent a simple inherited disorder.