Chromosome examination

Male fertility disorders can be hereditary. The chances of a hereditary disorder increase as sperm quality decreases. If there are no or very few spermatozoa present in the sperm (azoospermia/severe oligozoospermia), the chances of the man having a genetic disorder are roughly 10-25%. If our laboratory finds no or very few spermatozoa and there is no apparent external cause, we can conduct a genetic examination.

Genetic examination

This examination consists of two parts:

• Karyotyping

• DNA examination 

Karyotyping

Karyotyping means that all of the chromosomes in a cell, usually a blood cell, are coloured, counted using a microscope and examined individually. The major disorders that can be found are: an unusual number of chromosomes (46 is normal) or an irregularity in one or several chromosomes, such as having a missing piece that might have been lost (deletion) or transferred to another chromosome (translocation). Irregularities are most commonly found in men without spermatozoa, in which one of their two sex chromosomes is doubled or completely or partially missing. 

Klinefelter’s syndrome is the best-known example: patients suffering from this condition have two female sex chromosomes rather than one, which results in weak testicle function and little or no sperm cell production. Also, there may be consequences to testicle function and sperm cell production if part of the male (Y) chromosome is missing. And translocation, too, can have an influence on fertility: this may result in multiple miscarriages or children with one or more genetic abnormalities.

Translocations are known to happen in several family members. Therefore, it’s important to know whether there is a family history of fertility issues and/or children with birth defects.

DNA diagnostics

These past few years, DNA diagnostics have been on the rise: more and more disorders are revealed to be hereditary, and the cause of several diseases has been found in a small part of the chromosome: the gene. One example is cystic fibrosis, a genetic irregularity in a gene in chromosome number 7. This malfunctioning gene causes thick mucus in, among others, the airways and the pancreas. In many cases, the epididymis and ejaculatory duct are also involved in this disease: a developmental disorder may develop in the epididymis and ejaculatory duct, resulting in infertility. When there are spermatozoa being produced in the epididymis, pregnancy can (in some cases) be achieved using an ICSI treatment.

Y chromosome irregularities

Recently, a gene was found on the Y chromosome which is important in sperm cell production: the AZF-gene. Small errors in the order of the DNA molecules, known as mutations, may lead to a disordered sperm cell production. Mutations of the AZF-gene are found in 5-15% of men with low sperm quality. These mutations will be transferred to male offspring, causing them to develop the same fertility issues.