Читать книгу Assisted Reproduction Techniques - Группа авторов - Страница 51

Cystic fibrosis is the most common life‐threatening autosomal recessive condition in Caucasians, with an estimated carrier rate of 1 in 25 and incidence of 1 in 2,500. Common manifestations of cystic fibrosis are recurrent chest infections, chronic sinusitis and digestive problems leading to chronic diarrhea, malnutrition, poor growth and weight loss. Due to contemporary advances in medical treatment of the disease, the average lifespan of an affected person now extends well into the fourth decade of life, whereas in the past the disease was fatal in childhood or early adolescence.

Over 800 mutations in the cystic fibrosis transmembrane regulator (CFTR) gene have been identified, with a wide range of clinical phenotypes related to those mutations. The most common mutation in Western Europe is the delta‐F508 mutation, present in about 75% of affected individuals [1].

Approximately, 98% of men affected with cystic fibrosis are azoospermic, due to congenital bilateral absence of the vas deferens (CBAVD), blocking the transport of sperm from the proximal epididymis to the urethra [2]. CBAVD accounts for 6% of cases of obstructive azoospermia. In some otherwise healthy men, CBAVD could be the only phenotypic manifestation of cystic fibrosis. These men are now recognized as compound heterozygotes for a common (severe) mutation and a rare (but mild) mutation or carry two mild cystic fibrosis mutations. This condition is known as “genital cystic fibrosis” [3,4]. The male partner in Case History 1 belongs to this group, underscoring the importance of extensive molecular screening for cystic fibrosis mutations in men with obstructive azoospermia and CBAVD. Most (>95%) of men with only one cystic fibrosis mutation (true carriers) don’t exhibit CBAVD and are generally fertile as in the case of the male partner of the couple described in Case History 2.