Prenatal identification of mos45,X/46,X,+mar in a normal male baby by cytogenetic and molecular analysis

We report a case of mas 45,X/46,X,+mar, diagnosed prenatally by amniocentes is, whose physical examination, including external and internal organs, alo ng with serum testosterone values were normal five years after delivery. Th e mosaic karyotype was seen in 146 of 240 cells examined (amniotic fluid ce lls, 110/65; placental chorionic villi: 5/4; cord blood, 21/81; cultured sk in fibroblasts, 10/90) from 386 metaphases, and the marker chromosome appea red as a small non-fluorescent acrocentric chromosome. All autosomes appear ed normal, and no normal Y chromosome could be demonstrated. Analysis of 26 Y-chromosome loci by molecular techniques such as PCR, Southern analysis u sing multiple Y-specific DNA probes, and Hae III restriction endonuclease a ssessment of male-specific repeated DNA in the heterochromatic region of th e Y chromosome, and fluorescence in situ hybridization (FISH), revealed the marker was derived from a Y chromosome including p terminal to q11.23, and paracentric inversion in the remaining Y long arm. The formation of testes can be considered as existence of SRY (sex-determining region of Y) as a t estis-determining factor. The present report illustrates the importance of FISH and molecular techniques as a complement to cytogenetic methods for ac curate identification and characterization of chromosome rearrangements in prenatal diagnosis. Copyright (C) 1998 John Wiley & Sons, Ltd.