Clinical, cytogenetic and molecular analysis of three 46,XX males

Cytogenetic analysis, fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) were applied to characterize the Y-chromosomal breakpoints of three XX male patients. Two of these patients show a breakpoint within a protein kinase gene, PRKY, previously described as a hotspot of ectopic recombination between homologous regions on X and Y chromosomes during male meiosis. The slightly different clinical phenotypes of the three patients cannot be correlated with the localization of the breakpoints.

Screening of patients with Turner syndrome for "hidden" Y-mosaicism

The presence of Y-chromosomal sequences in the cells of patients with Turner-Syndrome (TS) is a risk factor for the development of gonadal tumors. Therefore and since demonstration of Y-material usually results in prophylactic gonadectomy optimal sensitivity and specificity of the diagnosis have to be attempted. We wanted to evaluate the diagnostic potential of cytogenetic investigations as routinely employed in TS. In the most comprehensive study published so far we screened 208 TS patients for the presence of Y-chromosomal sequences by polymerase chain reaction (PCR) specific for eight different loci along the Y-chromosome. Six patients (3%) without cytogenetic evidence of Y-chromosome were found to be Y-positive. Among 12 cases with marker chromosomes two more Y-chromosomal fragments were identified. Thus, PCR-screening for Y-specific sequences was shown to be a valuable tool in the clinical management of Turner patients.

A Turner-like phenotype in a girl with an isodicentric fluorescent Y chromosome mosaicism

BACKGROUND

The Ullrich-Turner syndrome (UTS) demonstrates a great clinical variability according to the cytogenetic and molecular genetic findings in various tissues. In few cases the karyotype reveals the presence of an additional Y-bearing cell line which is referred to as a borderline case of mixed gonadal dysgenesis. In this condition, Turner specific stigmata occur in about half of the cases.

PATIENT

A 10 year-old girl with short stature and only a few other signs of Turner syndrome and hypertrophic clitoris revealed 45,X/46,X,idic(Yq) mosaicism with 41% 46,X,idic(Yq) cells in a blood lymphocyte culture.

METHODS AND RESULTS

Fluorescence in situ hybridisation (FISH) technique, using alpha-satellite Y-chromosome specific probe for locus DYZ3, confirmed the isodicentric character of this structurally abnormal Y chromosome. Polymerase chain reaction (PCR) analysis using primers for eight loci along the Y chromosome including SRY (Sex determining Region, Y gene) were positive for all loci tested, indicating that sequences from the long arm, centromere and most of the short arm of the Y chromosome are present.

CONCLUSIONS

As patients with normal or rearranged Y chromosome have an increased risk of developing gonadal neoplasia prophylactic gonadectomy was performed in our patient. No evidence for gonadoblastoma was found on her streak-like gonads, but they showed some evidence of tubular formation. This paper points out the impact of cytogenetic and molecular genetic investigations in the definition of mosaicism in Turner's syndrome.