Globozoospermia

Globozoospermia
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Globozoospermia (also known as round-headed sperm syndrome) is a rare and severe form of monomorphic teratozoospermia. This means that the spermatozoa show the same abnormality, and over 85% of spermatozoa in sperm have this abnormality. Globozoospermia is responsible for less than 0.1% of male infertility. It characterised by round-headed spermatozoa without acrosome, an abnormal nuclear membrane and midpiece defects. Affected males therefore suffer from either reduced fertility or infertility. Studies suggest that globozoospermia can be either total (100% round-headed spermatozoa without acrosomes) or partial (20-60% round acrosomeless spermatozoa with normal sperm also identified in the sperm count,) however it is unclear whether these two forms are variations on the same syndrome, or actually different syndromes.

Studies have suggested mutations or deletions in three genes are responsible for this condition: SPATA16, PICK1 and DPY19L2. ICSI (intracytoplasmic sperm injection) has previously been used to assist reproduction in globozoospermic patients, however it has not been particularly effective in all patients, due to low fertilisation rates.

Table 1: Gene mutations that have been identified in globozoospermia and the impact these mutations have on sperm function and successful fertilization.

There are two types of globozoospermia:

Aside from the effect on fertility globozoospermia is symptomless. People with globozoospermia have normal physical and mental development, normal clinical features and normal hormonal profile.

The presence of round headed sperm in a semen analysis sample confirms the diagnosis of globozoospermia. The lack of acrosome can be ascertained by a technique known as immunofluorescence.

Until 1995, the only options for people with globozoospermia who wished to conceive were adoption or sperm donation. With the advancement of assisted reproductive techniques (ART) it is now possible for those with globozoospermia to conceive using their own sperm. The main technique used is intracytoplasmic sperm injection (ICSI) where fertilisation is achieved by a single sperm being injected into the egg. Some studies have shown it is possible for a viable embryo to be created with this technique alone, however others have found it necessary to also use calcium ionophore treatment for fertilisation to be successful. Calcium ionophore treatment is used to artificially activate the oocyte. This treatment may be necessary as globozoospermic sperm can be less likely to activate the oocyte, an important stage in fertilisation.

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