Absence of the Egg's Zona Pellucida: A Newly Identified Cause of Infertility

In 15% to 30% of infertile couples, no apparent cause is determined. Many experts believe that unexplained infertility results from defects manifested at or after fertilization or implantation. Now, investigators report an autosomal recessive form of infertility associated with abnormal eggs in a Chinese family.

In eggs of the index patient, absence of the zona pellucida was noted at workup for in vitro fertilization. A family history that included the index patient's siblings (five sisters and one brother) revealed known primary infertility in three of the sisters; in the eggs of the only one of these sisters who provided samples, the zona pellucida also was absent. The investigators searched for mutations in the four genes (ZP1, ZP2, ZP3, …