Bardet-Biedl Syndrome Health Article

Definition

Bardet-Biedl syndrome (BBS) is a condition that primarily affects vision, kidney function, limb development, growth, and intelligence.

Description

BBS expresses itself differently from person to person, even among members of the same family. However, certain features frequently appear.

Genetic profile

BBS is a genetically heterogeneous condition; this means that it has more than one known genetic cause. One of these causes is a mutation in the MKKS gene, located on chromosome 20. When working properly, this gene appears to produce a chaperonin, a factor needed to process proteins. Without the chaperonin, the proteins cannot work properly.

Using linkage analysis, researchers have connected some BBS cases to other chromosomes. Linkage analysis is a method of finding mutations based on their proximity to previously identified genetic landmarks. The specific genes responsible for these BBS cases remain unknown. However, several potential locations of BBS genes have been recognized. These sites are named for the number of the chromosome on which they are found, the arm of the chromosome ("q" for long arm, "p" for short arm), region of the arm, and band within the region. For example, "11q13" means chromosome number 11, long arm, region 1, band 3. In studies of families with BBS, researchers have found that a significant number of cases link either to 11q13, 15q22, or 16q21. In other families, researchers have linked BBS to either 2q31, 3p12, or 20p12. This last site is the location of the MKKS gene.

Regardless of the site involved, BBS displays an autosomal recessive inheritance pattern. This means that the condition occurs only when an individual inherits two defective copies of a BBS gene. If one copy is normal, the individual does not have BBS. This individual is called a carrier of BBS and can pass the gene on to the next generation.

Research indicates that people who inherit one abnormal BBS gene and one normal gene may be at risk for some of the health problems seen in BBS. Compared to the general population, these BBS gene carriers are more likely to develop high blood pressure, diabetes mellitus, and kidney disease, including kidney cancer.