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Chromosome Defects and Male Infertility

Chromosome abnormalities are increased in the infertile male and sub-fertile male compared to the general population. The incidence of chromosome abnormalities in the normal male population is estimated to be approximately 0.5 %, where as a study of 9766 infertile males showed an incidence of 5.8 % (4.2 % sex chromosome abnormalities and 1.5 % autosome abnormalities (1)). Numerical abnormalities of the sex chromosome and structural abnormalities of sex chromosomes and autosomes have been described. Klinefelter’s Syndrome (47, XXY) is the most frequent chromosome anomaly, occurring in 1/500 male births and accounts for approximately 14 % of all cases of azoospermia. 10% are mosaics 46,XY/47,XXY and the rest 47, XXY. Maternal or paternal non-disjunction is the cause. Patients may have increased height, lower extremity varicosities, decreased intelligence, diabetes, obesity increased incidence of leukemia, non seminomatous extragonadal germ cell tumors, and infertility. Gynecomastia and breast cancer have been reported (2).

Mosiacs have variable sperm production and pregnancies have been reported. Males with XYY (1/1000 births) may have impaired spermatogenesis, antisocial behavior or decreased intelligence. Patients with mixed gonadal dysgenesis (45, X/46, XY) may present as normal male, female, or ambiguous. The XX male syndrome (1/20000 births) presents with azoospermia. They are typically male in appearance and have neither internal or external female genitalia. Most likely, a fragment of the Y bearing SRY is translocated to a homologous location on X. Also, a mutation of an X gene that inhibits an autosomal testis determining gene could lead to this phenotype. Noonan Syndrome was once called ‘male Turner’s Syndrome due to some phenotypic similarities with female 45,X may have male infertility. No consistent common chromosome anomaly is seen but chromosome 12 may be involved (3). An interesting phenomenon with genetic imprinting (chromosomal source of inherited genes) is seen with Prader-Willi Syndrome where hypogonadism is noted. Several genes on 15q11-q13 are expressed only from the paternal chromosome and most cases result from deletion of paternal 15q10-q13 or uniparental disomy of the maternal allele.

Autosomal abnormalities include Robertsonian and reciprocal translocations, paracentric inversions and marker chromosomes. Heterozygotes for translocations are 7 times more frequent in infertile males and Robertsonian (13:14) is found in 60 % (4). Paracentric inversions in chromosomes 1,3, 5, 6, and 10 may interfere with meiosis resulting I a decreased capacity to produce sperm (4).

Microdeletions of Yq cause varying defects in spermatogenesis indicating the importance of this region to male fertility. In the case of a deletion of the Y chromosome, the infertility would be inherited by the male children. Not all labs do this type of testing. Most labs are capable of testing for chromosome abnormalities.

Because of the data above and the potential implications for the offspring, we should consider genetic testing for the male with significant abnormalities of sperm.

References:

1. Johnson MJ. Genetic risks of intracytoplasmic sperm injection in the treatment of male infertility: recommendations for genetic counseling and screening. 1998. Fertil. Steril. 70:397-411.

2. Maduro MR, Lamb DJ. Understanding the new genetics of male infertility. 2002. J. Urology. 168: 2197-2205.

3. Nieschlag E, Behre HM, Meschede D, Kamischke A. Disorders at the Testicular level. In Andrology; Male reproductive health and dysfunction. Eds, E Nieschlag, HM Behre. Springer. Berlin. 1997. pp.133-157.

4. Huynh T, Mollard R, Trounson A. Selected genetic factors associated with male infertility. 2002. Hum. Repro. Update. 8(2):183-198.
 

 

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