Is there a correlation between the proportion of cells with isodicentric Yp at amniocentesis and phenotypic sex?

Objectives: (1) To present a case with prenatally detected idic Yp. (2) To review literature to assess if there is a correlation between the proportion of amniocytes with idic Yp and phenotypic sex.

Methods: Seventeen cases were reviewed.

Results: Amniocentesis was done due to positive integrated prenatal screening result. Interphase FISH was normal for chromosomes 13, 18, and 21, but mosaic for cell lines with 1 X and 0 to 2 copies of DYZ3, SRY, or DYZ1(Yq12). Amniocytes had 45,X[28]/46,X,idic(Y)(q11.2)[2].ish idic(Y)(DYZ3 + +, SRY + +). An apparently normal female was born at 37 weeks. The umbilical cord had 45,X[50], but cord blood had 45,X[17]/46,X,idic(Y)[31]/47,X,idic(Y)x2[2]. Review of 17 cases showed that 13 cases with 20 to 100% cells with idic Yp all had a male phenotype. Two cases with 3 and 7% of idic Yp cells had a female phenotype. Two cases with 45,X only at prenatal diagnosis but idic Yp detected postnatally were phenotypic male.

Conclusion: (1) We present the first report of prenatally detected idic Yp and Yq12 resulting in an apparently normal female at birth. (2) Finding of > 20% of G-banded amniocytes with idic Yp in the absence of other indicators of foetal structural anomalies seems to correlate with phenotypically normal male in most cases.