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Autosomal Recessive Inheritance

Drawing illustrating autosomal recessive inheritance of Bietti's Crystalline Dystrophy. Illustration shows a father carrier and a mother carrier with four offspring: one unaffected non-carrier, one unaffected carrier, two unaffected carriers, and one affected.

Autosomal recessive inheritance is the most common type of inheritance for retinal dystrophies. When this type of condition is present in a family, it is often seen only in one child or in siblings, not in the parents or other relatives.

As shown in the figure, to have symptoms of BCD, an individual must have two copies of the same disease gene. We all have two copies of each gene, since we inherit one from our father and one from our mother.

In the figure above, the N stands for the normal copy of the BCD gene and the B stands for the abnormal copy of the BCD gene. Both parents have an N gene and a B gene and are therefore called "carriers." In this scenario, there is a 75 percent chance that a child will not have Bietti's crystalline dystrophy. In each child there is a 50 percent chance to inherit the N gene and a 50 percent chance to inherit the B gene from each parent. There is:

These recessive genes can be passed on for generations without causing disease, since two copies are needed to cause symptoms.

Department of Health and Human Services NIH, the National Institutes of Health