Many autosomal recessive conditions occur this way. As mentioned above, a person who carries one copy of an autosomal recessive gene is usually not aware they carry the gene, because they do not show any signs of the disease or condition. It is estimated that all people carry about 20 recessive genes that cause genetic diseases or conditions. Usually a person does not know they carry a recessive gene unless they have the disease in their family, or if they have had an affected child. Examples of autosomal recessive disorders include cystic fibrosis, sickle cell anemia, and Tay Sachs disease.
Cystic fibrosis is one of the most common inherited single gene disorders in Caucasians.
People with CF secrete abnormal body fluids, including unusual sweat and a thick mucus which prevents the body from properly cleansing the lungs. The mucus interrupts the function of vital organs and leads to chronic infections. Classic CF also involves the pancreas and causes decreased absorption of essential nutrients. Life expectancy has improved, but, ultimately, death most often occurs from respiratory failure. Other people with variants of CF may have only lung involvement, sinusitis, or infertility.