Chromosomal Abnormalities Related to Infertility and Sexual Development Disorders in Boys

  


    
Abnormal    Karyotypes (88 cases)

    
Freq. in all cases (%)

    
Freq.    in all anom (%)

  

  


    
47,XXY x30


      48,XXXY


      48,XXYY


      46,XY/47XXY x5


      47,Xi(Xq)Y x3


      46,XY/46,X /47,XXY x2


      46,XY/46,XX/47,XXY x4


      46,XY/47,XXY,del(13q22)


      Total

      
46,XY/45,X x11


        46,XY/46,XX x4


        46,XY/46,XX/45,X


        46,XY/46,XX/46,Xi(Xp)


        Total

      
46,XY,Yq+ x4


        46,X,del(Yq11) x3


        46,XY,del(Yq),t(9;22)(q34;q1)


        45,X,t(3;Y)(p11;p11)


        46,XY,inv(Y)(q12;q11)


        Total

      
46,XY,inv(9)(p11;q12) or    (p12;q13) x10


        46,XY,inv(5),del(12p13)


        46,XY,robt(14;15)


        46,XY, anop(%15)

      
Total

      
46,XX males (sex revelsal) x2 Total

    
9.9


      0.3


      0.3


      1.7


      1.0


      0.7


      1.3


      0.3


      15.6

      
3.6


        1.3


        0.3


        0.3


        5.6

      
1.3


        1.0


        0.7


        0.3


        0.3


        3.3

      
3.3


        0.3


        0.3


        0.3


        4.3

      
 

      
0.7

    
34.1


      1.1


      1.1


      5.7


      3.4


      2.3


      4.5


      1.1


      53.4

      
12.5


        4.5


        1.1


        1.1


        19.3

      
4.5


        3.4


        2.3


        1.1


        1.1


        11.4

      
11.4


        1.1


        1.1


        1.1


        14.8

      
 

      
2.3

  

Table 2: Classification of chromosomal anomalies in infertile men with abnormal karyotype.

Discussion

Although the genetic basis underlying sexual development disorders and infertility is largely unknown, numerical and structural CAs play a major role in these disorders. Genetic causes include Y and X chromosome deletions, single gene disorders, chromosomal aneuploidies, structural and numerical CAs, and multifactorial causes. Numerical and structural CAs played a principal role in male infertility. Chromosomal aneuploidies are the leading cause of pregnancy loss and developmental disorders, and men with numerical or structural karyotype abnormalities may also produce aneuploid sperm. Gonosomal aneuploidies (X and Y) are the leading cause of pregnancy loss and developmental disabilities in humans, such as Klinefelter syndrome (47,XXY) are the most frequent CA in infertile men. We also reported the most common gonosomal aneuploidies (XXY) in patients boys. In this study, gonosomal aneuploidy (Klinefelter syndrome) was found to be 15.6% among all cases and 53.4% among all anomalies. Classical karyotype (47,XXY) was found to be 63.8% in children with KS. This is followed by mosaics (46,XY/47,XXY, 14.8%), isochromosome X (47,Xi(Xq), 3.4%), rare X and Y aneuploidies (48,XXXY and 48,XXYY, 2.3%) and others [46,XY/47,XXY,del(13q22), 1.1%]. In a similar study, it was also reported that approximately 80% of KS patients had 47,XXY karyotype, and 20% of other sex-chromosome numerical abnormalities (48,XXXY, 48,XXYY, 49,XXXXY), mosaics and structural sex chromosome damages (11). The extra X chromosome is sporadically due to the failure of gametogenesis to separate during the first or second meiotic division or due to mitotic segregation in the developing zygote. Boys with 47,XXY have variable phenotypic characteristics. Most cases showed the classic, well-defined phenotype, while others had various sexual behavior problems, mental retardation and developmental delay. Infertility, hypogonadism and similar complaints were also recorded in our cases. The cases with classic KS (47,XXY) or mosaic variants have severely impaired spermatogenesis, typically small and firm testicles with hyalinization of the seminiferous tubules and consequent spermatogenic failure.

Chromosomal defects were found to be twice as high in infertile men as compared to controls [12]. It has been found that at least 5% of azoospermic men have 47,XXY aneuploidy [13]. These cytogenetic damages affect semen quality and cause varying degrees of male infertility. Testicular atrophy and decreased sperm count in patients with KS can theoretically be attributed to atresia of germ cells caused by the extra X chromosome [14,15]. The classic form of KS accounts for around 11% of azoospermic individuals, whereas mosaic individuals often present with oligozoospermia [16]. Other Klienfelter mosaic types are seen in azoospermic and oligozoospermic men [17]. Testicular atrophy and decreased sperm count in patients with KS can theoretically be attributed to atresia of germ cells caused by the extra X chromosome [14,15]. Mosaic sex chromosome karyotypes are common and many combinations are possible. We found mosaic karyotypes related to X chromosome increase in 25.5% of KS cases and 4.0% of all cases. At the same time, there were 4.3% of individuals in the KS group who had 47,XXY karyotype as well as less frequently one or two additional X and/or Y chromosomes (48,XXYY and 48,XXXY). It can be said that the high incidence of mosaic sex chromosomal aneuploidies in our patient group is associated with infertility and other clinical symptoms. With this, various mosaic patterns constitute approximately 15% of patients, the most common being 46,XY/47,XXY and the remainder are increases of the X chromosome (48,XXXY or 49,XXXXY). X-chromosome polysomies, isochromosome Xqi(Xq) or X-Y translocations, which are rare, are encountered in 0.3-0.9% of men with KS [18,19]. In the current study, structural irregularity in the form of the long arm isomer of the X chromosome [i(Xq)] was detected in three (6.4%) of the KS cases and 1% of all cases. It has been shown by observations on other structural anomalies of X chromosomes that the presence of additional material of Xq causes azoospermia and hormonal imbalance in males [20]. In general, those with ovarian failure have breakpoints within the Xq13-q26 region.

At the same time, besides the 47,XXY karyotype, a less frequent group of KS patients have additional X and/or Y chromosomes and show karyotypes like 48,XXYY, 48,XXXY or 49,XXXXY. 4.3% of our KS cases had 48,XXXY and 48,XXYY variants. The strongest known genetic marker for infertility in some men is the Y chromosome. The Y chromosome contains genes necessary for gonadal differentiation into a testis and genes for complete spermatogenesis. With this, extra copies of genes from the pseudoautosomal region of the extra X and Y chromosome contribute to the signs and symptoms of 48,XXYY syndrome. At the same time, the presence of the X chromosome results not only in spermatogenic and androgenic failure, but also in gynecomastia, expression language difficulties, higher mortality from breast cancer and non-Hodgkin lymphoma, and a higher incidence of extragonadal germ cell tumors [21-23]. There is a large amount of phenotypic variability among 46,XX/46,XY mosaic individuals. The spectrum of sexual development in these mosaic individuals ranges from typical sexual development to various. It is possible that a large percentage of XX/XY mosaics are phenotypically male or female. We found that 5.6% of all cases and 19.3% of all anomalies were sex chromosome mismatch, that is, individuals with both XX and XY cell lines. These cases had congenital irregularities including incomplete intrauterine masculinization, micropenis or atypical development of gonadal or anatomical sex, such as female external genitalia. Sex chromosome mismatch refers to individuals with both XX and XY cell lines. This mix of sex chromosomes can be explained by three genetic mechanisms; 46,XX/46,XY may be mosaic-based, most commonly by in utero combination of two fertilized zygotes, or cells may be fertilized by an X and a Y sperm, respectively [24,25]. Patients with mixed gonadal dysgenesis have a broad phenotypic spectrum including normal women or women affected with Turner's syndrome, men with hypospadias, and male or female pseudohermaphrodism. Pseudohermaphrodite describes individuals whose gonadal sex is compatible with chromosomal structures but with atypical development of external genitalia. The 46,XY differences in sex development may result from either decreased testosterone and/or DHT synthesis or impaired androgen effect. DSD is characterized by micropenis, atypical or female external genitalia caused by incomplete intrauterine masculinization in the presence or absence of Müllerian structures. Most 46,XY DSD-patients have male gonads, but some lack gonadal tissue. Complete absence of virilization results in normal female external genitalia. These patients usually seek medical attention at puberty because of the absence of breast development and/or primary amenorrhea. The presence of both testicular and ovarian tissue (ovotesticular disorder) has been reported in 46,XX/46,XY mosaic cases [26]. 46,XX/46,XY individuals have one or more irregularities such as a small phallus midway in size between the clitoris and penis, an incompletely closed urogenital opening, and an abnormal urethral opening on the perineum. Although some people with 46,XX/46,XY have ovarian tissue and testicular tissue at the same time, both gonads are not functional. A mix of male and female traits may emerge at puberty.

Structural CAs are an important cause of miscarriage, infertility, congenital anomalies and mental retardation in humans. The frequency of Y chromosome structural rearrangements was also found to be higher than the frequency observed in newborn series. Some cases of Y chromosome structural rearrangements are known as a result of failure of pairing between X and Y chromosomes. We found deletions in the long arm (q11, q12) of the Y chromosome in four (1.3%) of our cases. Deletion of the Y chromosome region containing the azoospermia factor is considered the most common genetic cause of male infertility. The Y chromosome contains several genes required for spermatogenesis and loss of one or more of such genes can cause impairment of this process. The long arm of the Y chromosome contains many sequences that predispose it to self-recombination during spermatogenesis, thus making it susceptible to intrachromosomal deletions. Such deletions lead to copy number variation that leads to male sterility. In individuals with gonadal dysgenesis that bear a full or even partial fragments of Y chromosome have a high risk of developing gonadal tumours specifically gonadoblastoma [27-29]. Other karyotype abnormalities Infertile men can have other Y chromosome abnormalities including mosaicism, ring Y, deletion Y, and isodicentric Y. Deletion is a type of mutation involving the loss of genetic material. The Y chromosome contains several genes required for spermatogenesis and loss of one or more of such genes can cause impairment of this process. After the Klinfeleter syndrome, Y chromosome micodeletion are the second most frequent genetic cause of infertility. Three regions on the long arm of the Y chromosome (AZFa, AZFb and AZFc) are known to be deleted in men with severe spermatogenic deficiency. The frequency of these microdeletions in azoospermic and severely oligospermic men is between 1% and 50% [30,31]. Patients with deletion Y chromosomes should undergo AZF microdeletion assays to determine if these regions are present.

We found that the long arm of the Y chromosome was longer than normal in four cases (1.3%). Few reports on male infertility have mentioned chromosomal polymorphisms or variants. These minor CAs are considered to have no clinical impact. One study reported that the increased long arm (Yq+) polymorphism of the Y chromosome was 4.4% [31] Whether chromosomal variants may alter the carrier's fertility is still an open question, as is the role of heterochromatin in meiosis. We reported that the Y chromosome was translocated to chromosome 3 in one case. Thus, a previous study revealed the cytogenetic effects on patients with infertility in a Turkish population, and the 1qh+, 16qh+, Yqh+ and inv(9) polymorphisms had frequencies of 0.5%, 1.5%, 1.82% and 0.5% respectively [32]. In addition, it has been reported that Yq+ may be associated with the risk of unexplained recurrent miscarriages and may play an important role in the development of these abortions [33]. All these findings indicate that Yq+ may be associated with the risk of the risk of infertility or SDD, may act an important role in the developm ent of these diseases.

Other chromosome damages that can cause infertility can include translocations and inversions. It is now known that some reciprocal translocations are associated with failure or disruption in sperm production. It has been reported that approximately seven times more Robertsonian heterozygotes are present in infertile couples [34]. Robertsonian and reciprocal translocations are found more commonly in the oligospermic than the azoospermic population [35]. In addition to X and Y chromosomes, some autosomal genes also play a role in determining sex [36]. Autosomal CAs are relatively common in humans. These may be numerical and structural CAs. These abnormalities are known to be associated with infertility, increased pregnancy loss, and birth of disabled children. The frequency of autosomal CAs in infertile men ranges from 3% to 19%: 3% in mild infertility cases and 19% in men with non-obstructive azoospermia [37].

We found inversion type autosomal and gonosomal structural irregularities in twelve (4.0%) of our cases. Chromosomal inversions can also cause infertility, spontaneous abortions and birth defects. Because inversions produce somewhat unstable gametes, they can interfere with sperm count and fertility. Studies on unbalanced gametes in balanced inversion carriers have been scarce, although few studies have reported unbalanced sperm ranges between 1% and 54% [38,39]. Pericentric inversions of the Y chromosome are quite common, with most cases being familial, with an estimated incidence in males of 0.6-1:1,000 in the general population. We also detected paracentric inversion Y in one case. Although it is known that the risk of mental retardation or miscarriage is not significantly increased in pericentric inversion Y carriers and there are no abnormal phenotypic features, this chromosomal damage should still be considered. Inversions are risky for the offspring and not the carriers, a carrier of either type of inversion is at risk of producing abnormal gametes. On the other side, pericentric inversions of chromosome 9 are a common occurrence. Most of the observed inv(9)s are not believed to cause any specific phenotypic abnormality. However, some studies have been associated with phenotypic disorders. Carriers of large pericentric inversions are at risk for meiotic recombination within the inverted segment, resulting in duplication or deletion of chromosomes in the gametes. If crossing-over occurs, unbalanced or abnormal gametes may result. Gametes with the unbalanced inversion may cause spontaneous fetal death and malformed offspring. Many studies have reported that inv(9) was closely associated with recurrent spontaneous miscarriage, infertility, congenital anomalies, and idiopathic reproductive failure [40-42]. As a matter of fact, we noted that in our cases, there were complaints of infertiliy, SDD and abnormal clinical conditions. All these findings show that inv(9) is not as harmless as it seems. Although the breakpoints of our cases were different, we think that the chromosomes have a high tendency to be exposed to inversion. We detected inv(9) in 10 cases (3.3% among all cases and 11.4% among all anomalies). The most widely recognized inversion is 46,XY,inv(9)(p11;q13) in oligozoospermic infertile male. Inversion of chromosome nine could be acknowledged as a reason of fertility problems. Similarly, 46,Y,inv(X)(q12;q25) inversion has been reported in an infertile man with a Klinefelter-like phenotype. On the other hand, pericentric inversion of chromosomes 1, 3, 5, 6 and 10 is related to abnormal sperm production in infertile men.

Loss of the short arms of acrocentric chromosomes does not have phenotypic consequences, because the lost sections do not contain unique genetic sequences. However, unbalanced gametes of heterozygous carriers are common and give rise to a monosomic or trisomic fetus. Most monosomies and trisomies are lethal and spontaneously abort early in the pregnancy. We found autosome-autosome translocation [14,15] in one case. Autosome-autosome translocations cause decreased fertility and the translocated chromosomes to synapse in meiosis. The most common Robertsonian translocation observed in infertile males is t(13q14q). t(13q14q) and t(14:21) revealed abnormal behavior of autosomes rearranged in meiosis causing infertility during spermatogenesis in infertile carriers [43]. All this information confirms that the autosomal translocation we found in our case may cause infertility and and genital disorders.

Conclusion

The rates of chromosomal abnormalities in children with suspected chromosomal disorders were shown. This study concludes that chromosomal defects are significantly associated with infertility and genital disorders. Moreover, this study needs to be confirmed with further investigations the role of chromosomal aberrations in the etiology of infertility and genital ambiguity. The chromosomal analysis is an important investigation in male with infertility and genital ambiguity. Therefore, it is recommend that for better counselling, chromosomal analysis should be done in all cases of infertility and suspected abnormalities. In the remaining patients where no chromosomal abnormality can be detected, other possible causes of defects e.g. single gene defect, multifactorial or environmental factors need to be probed in order to find possible management strategies.

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