Dynamic mosaicism manifesting as loss, gain and rearrangement of an isodicentric Y chromosome in a male child with growth retardation and abnormal external genitalia.

Isodicentric chromosomes are considered the most common structural abnormality of the human Y chromosome. Because of their instability during cell division, loss of an isodicentric Y seems mainly to lie at the origin of mosaicism in previously reported patients with a 45,X cell line. Here, we report on a similar case, which, however, turned out to be an example of dynamic mosaicism involving isodicentric chromosome Y and isochromosome Y after FISH with a set of chromosome Y-specific probes and multicolor banding. Cytogenetic analyses (GTG-, C-, and Q-banding) have shown three different cell lines: 45,X/46, X,idic(Y)(q12)/46,X,+mar. The application of molecular cytogenetic techniques established the presence of four cell lines: 45,X (48%), 46,X,idic(Y)(q11.23) (42%), 46,X,i(Y)(p10) (6%) and 47,X,idic(Y)(q11.23),+idic(Y)(q11.23) (4%). According to the available literature, this is the first case of dynamic mosaicism with up to four different cell lines involving loss, gain, and rearrangement of an idic(Y)(q11.23). The present report indicates that cases of mosaicism involving isodicentric and isochromosome Ys can be more dynamic in terms of somatic intercellular variability that probably has an underappreciated effect on the phenotype.

Iourov IY ，Vorsanova SG ，Liehr T ，Monakhov VV ，Soloviev IV ，Yurov YB ... -  《-》

Evidence of a mechanism for isodicentric chromosome Y formation in a 45,X/46,X,idic(Y)(p11.31)/46,X,del(Y)(p11.31) mosaic karyotype.

Abnormalities involving sex chromosomes account for approximately 0.5% of live births. The phenotypes of individuals with mosaic cell lines having structural aberrations of the X and Y chromosomes are variable and hard to accurately predict. Phenotypes associated with sex chromosome mosaicism range from Turner syndrome to males with infertility, and often present with ambiguous genitalia. Previous studies of individuals with an 45,X/46,X,idic(Y)(p11) karyotype suggest that the presence of both cell lines should result from an intermediate, 46,XY cell line. Here we report a 2.5 year old female with phenotypic features of Turner syndrome with an isodicentric Y chromosome and a cell line with a deleted Y with a final karyotype of 45,X/46,X,idic(Y)(p11.31)/46,X,del(Y)(p11.31). Fluorescence in situ hybridization (FISH) mapping of the Y chromosome breakpoint revealed very low percentages of the deleted Y cells, but suggested a potential mechanism for the formation of the isodicentric Y chromosome. To our knowledge, the 46,X,del(Y) intermediate cell line in our patient has not been previously reported in individuals with mosaic sex chromosome structural abnormalities.

Reshmi SC ，Miller JL ，Deplewski D ，Close C ，Henderson LJ ，Littlejohn E ，Schwartz S ，Waggoner DJ ... -  《-》

Mixed gonadal dysgenesis with 45,X/46,X,idic(Y)/46,XY,idic(Y) karyotype.

Caglayan AO ，Demiryilmaz F ，Kendirci M ，Ozyazgan I ，Akalin H ，Bittmann S ... -  《genetic counseling》

Phenotypic variability in isodicentric Y patients: study of nine cases.

DesGroseilliers M ，Beaulieu Bergeron M ，Brochu P ，Lemyre E ，Lemieux N ... -  《CLINICAL GENETICS》

Clinical and molecular cytogenetic studies in three infertile patients with mosaic rearranged Y chromosomes.

Bettio D ，Venci A ，Rizzi N ，Negri L ，Setti PL ... -  《HUMAN REPRODUCTION》