Clinical and Genetic Analysis of an Infertile Male with 46,XX/46,XY Chimerism.

The sex chromosome-discordant chimerism 46,XX/46,XY is rarely found in humans with a phenotypically normal appearance, and this lack of phenotypic changes and the rarity of chimerism make it difficult to identify its exact incidence. Here, we report a case of this sex chromosome-discordant chimerism diagnosed by cytogenic and molecular analyses of peripheral blood in a phenotypically normal male who was referred to our facility for infertility. Based on the karyotype, fluorescence in situ hybridisation (FISH) and short tandem repeat (STR) analyses, the type of this chimerism was determined to be tetragametic presenting four alleles at two loci on chromosomes 16 and 21.

Prenatally Diagnosed Rare Trisomy 16 Mosaicism in Human Amniotic Fluid Cells in the Second Trimester: A Case Report.

Although trisomy 16 is commonly detected in spontaneous abortions and accounts for over 30% of cases of autosomal trisomy detected after spontaneous abortion, trisomy 16 mosaicism is rarely detected by amniocentesis in the second trimester. Here, we report a case of level III trisomy 16 mosaicism (47,XX,+16[8]/46,XX[31]) diagnosed by cytogenetic analysis of independently cultured amniotic fluid cells. The female baby was delivered at full term with low birth weight and intrauterine growth retardation, and interestingly, her karyotype was normal (46,XX). Given the difficulty in predicting the outcomes of fetuses with this mosaicism, it is recommended to inform the possibility of mosaicisms including this trisomy 16 mosaicism during prenatal genetic diagnosis and genetic counseling for parents.