Recurrence of triploidy in a woman with low level 45,X mosaicism

Abstract

Triploidy (69 chromosomes) occurs in 1 to 3% of recognized pregnancies typically resulting in first trimester spontaneous abortion. The recurrence risk after one affected pregnancy is 1-1.5%. Triploidy can be diandric or digynic in origin. Diandric triploids result from dispermy or fertilization from a diploid sperm. Diandric triploids result in a partial hydatidiform mole. Digynic triploids may be due to a complete nondisjunctional event during oogenesis, retention of a polar body or fertilization of an ovulated primary oocyte. Digynic triploids may survive to the second trimester and develop as a growth retarded fetus with a small placenta. We report a woman with four first trimester spontaneous abortions of which three were triploid. The first miscarriage was not karyotyped, the second showed 69.XXX, the third 69.XXY and the fourth 69,XXX. Parent of origin studies were not performed, so it is unclear whether the triploid conceptions were diandric or digynic in origin. The proband also has a normal son. Chromosomal analysis on the proband showed 45,X[3], 46,XX[27]. Although nondisjunction is reported among offspring of Turner mosaics, we are not aware of any other reports of recurrent triploidy associated with low level sex chromosome mosaicism in the mother. The triploidy may be directly correlated with Turner mosaicism or may represent a random association.