Answer from: Douglas Lester, PhD, MSc, BSc (Hons)
With complex disorders or syndromic infertility, you usually have other physiological problems other than infertility—for example, the Deafness Male Infertility Syndrome. This is caused by a large deletion of millions of letters of DNA and chromosome 15. This deletion is very common in the human population; as many as 1.6% of all human chromosomes have been shown to have such a deletion of one of their chromosomes fifteens, so it’s not a sex chromosome. However, all of these carriers are unaffected as you need two bad copies of chromosome 15 to develop a syndrome. This large deletion includes letters for both ears specific STRCG and its near neighbour, the sperm-specific gene, CATSPER2. Male and female patients who have such deletions on both chromosomes how progressive hearing loss from birth. But unfortunately, males usually suffer from reduced fertility and sperm, none of which are able to fertilize naturally or by traditional IVF. The only method for successful fertilization for them is direct sperm injection or ICSI, that’s an example of syndromic deafness and male fertility. There are countless other syndromic causes; that’s just one example.
Complex genetic disorders - how do they impact my fertility?
Even a single gene defect can lead to some health conditions that can, in turn, cause problems with your fertility. Also, abnormal chromosomes can be a direct cause of male infertility.