Document Type : Case Report
1 Molecular Medicine Unit, Azienda Ospedaliera Universitaria Senese, Siena, Italy;Medical Genetics, Misericordia Hospital, Grosseto, Italy
2 Diagnostic Genetic Unit, Department of Laboratory, Careggi University Hospital, Firenze, Italy
3 Medical Genetics, Misericordia Hospital, Grosseto, Italy
4 4Department of Molecular and Developmental Medicine, University of Siena, Azienda Ospedaliera Universitaria Senese, Siena, Italy
5 5Genitourinary Unit, University of Siena, Azienda Ospedaliera Universitaria Senese, Siena, Italy
Chromosome anomalies contribute frequently to reproductive failure in men, accounting for approximately 7% of all infertility cases and 10-15% of azoospermia (
An apparently healthy man, 34-year-old, attended our services after a two years history of infertility. An informed consent was obtained from the patient after the aims and procedures of the investigation were fully explained. He appeared as a well-developed male, 170 cm tall, weighing 68 kg. Physical examinations revealed normal male habitus except for a high-pitched voice and testis slightly smaller in size: at scrotal echography, the right testis was evaluated about 15 ml in volume and the left approximately 12 ml. Repeated semen analysis revealed azoospermia. Endocrinological examinations showed hypergonadotrophic hypogonadism, with elevated follicle stimulating hormone (FSH, 24.6 mU/ml), moderately low total serum testosterone level (2.74 ng/ ml), very low free testosterone (3.74 pg/ml), and normal levels of sex-hormone-binding globulin (34.8 nmol/l) and luteinizing hormone (LH, 4.2 mU/ml). The patient, who received preand posttest genetic counselling, refused a testicular biopsy for diagnostic purposes and the possibly recovery of germ cells.
High-resolution chromosome analysis [Quinacrine (QFQ) banding] was performed from blood lymphocyte cultures according to standard cytogenetic procedures. FISH was carried out according to manufacturer’s instructions, using centromeric probes for chromosomes Y (DYZ3, Yp11.1-q11.1; Kreatech Diagnostics) and 13/21 (D13Z1/D21Z1, 13p11.1-q11.1 and 21p11.1-q11.1; Kreatech Diagnostics), subtelomere-specific probes for both arms of the sex chromosomes (DXYS130, Xp/Yp telomeres; DXYS224, Xq/Yq telomeres; Kreatech Diagnostics) and probes for the whole chromosome Y and 21 (Kreatech Diagnostics). Lymphocyte preparations from male with normal karyotype were used as controls for the FISH assays.
Array-CGH was performed using the Human Genome CGH 4X180K Microarray Kit (Agilent Technologies, USA), according to the manufacturer’s protocols. The Agilent Feature Extraction software has been used to perform image analysis. In order to correct systematic spatial and intensity biases, the results were normalized using the lowess function. Normalised log2ratio values were calculated and breakpoint identification was performed applying the Shifting Level Model (SLM) segmentation algorithm (
In our patient, the Y chromosome was not detectable at a first conventional chromosome analysis, revealing the appearance of a 45,X0 karyotype. As the result was inconsistent with the phenotype of the patient and some additional material detected on the terminal part of 21p chromosome, might be suspected of Y-derived material, we applied FISH analysis. By this approach, we detected a derivative chromosome originating from a fragment of the short arm of the chromosome Y translocated on the short arm of the 21 chromosome (
A patient’s metaphase fluorescence in situ hybridization (FISH) image showing a 45,X karyotype due to the loss of chromosome Y: the red probe identifies the Xq and Y q subtelomere regions (marker DXYS224), the green probe identifies Xp and Y p subtelomere regions (marker DXYS130). A. FISH detail of X and 21 cromosomes shows the green signal at the p-telomere of the X chromosome and at the p-telomere of the derivative chromosome 21 The probe for the long arms of the Y and X chromosomes (red signal) shows fluorescence illumination only of the tip of the long arm of the chromosome X (normal X chromosome): the red signal to be referred to Yq is missed and B. Detail of Quinacrine (QFQ) and FISH of the 21 chromosomes. The FISH probe of the Yp (labelled in green) results to be translocated to the distal short arm of the derivative chromosome 21, while the normal chromosome 21 shows only the counterstained 21-chromosome painting probe (labelled in red).
As a whole, the derived chromosome could be described by FISH as [45,X,der(
Chromosome Y array comparative genomic hybridization (array-CGH) plot. The area highlighted in red shows the loss of about 45 Mb of the chromosomal region Yq11.21-q12 spanning from 13,992 kb to 59,031 kb (according to UCSC Genome Browser GRCh37/hg19).
Chromosomal imbalances can severely affect male fertility. The prevalence of karyotype abnormalities in infertile males are reported about 8-10 fold higher than in general population (
Due to the complexity of the information regarding his genetic status, as previously agreed with patient, he was seen in several rounds of genetic consultation after the test, alone and in the company of his partner, to disclose the result and to discuss all the possible implications. As we inform that sperm retrieval from a testicular biopsy is considered ineffective for males with such a Y chromosomal deletion (entire AZF region), a more invasive evaluation was refused and no testicular tissue studies were performed for histological examinations. Overall, the patient did not show adverse psychological reactions after the disclosure of genetic information: he did not exhibit anxiety and/or depression symptoms and refused a proposed psychological support as considering it unnecessary. These findings are consistent with the notion that the psychological distress associated with the communication about positive genetic test results may be reduced by careful pre- and post- test genetic counseling.
Our study, discussing a new case of a rare Y;21 unbalanced translocation, highlighs the usefulness of the high-throughput molecular diagnostic methods for detection of subtle chromosomal rearrangements. To our knowledge, this is the first case in which a (Yp;21p) translocation has been ascertained using an array-CGH approach, thus reporting details of such a rearrangement at higher resolution.