Atrophy spinobulbar Kennedy (bulbar muscular atrophy and Spinal - Kennedy Disease-) - Gen AR

Spinobulbar muscle atrophy is a disorder of motor neurons characterized by weakness and muscle atrophy, beginning in adulthood, which is compounded over time. Muscle atrophy causes arms and legs cramps, difficulty in walking and tendency to fall. They can also be affected some facial and throat (bulbar muscles) muscles, causing progressive problems swallowing and speech. In addition, there are frequent muscle twitches. Some men have an abnormal breast development (gynecomastia) and can be infertile.

The genetic basis of this disease resides in AR gene mutations (Androgen Receptor). This gene, located on the long arm of chromosome 12 (Xq12), encodes a protein called androgen receptor (Androgen Receptor). Androgens, such as testosterone, are important for normal male sexual development before birth and during puberty. Genetic alteration found in this disease involves repetitions CAG expanding abnormally gene. Under normal conditions this triplet is repeated from less than 10 times to 36 times, while in affected individuals of spinobulbar muscular atrophy is repeated at least 38 times can reach up to 60 times, and even double or triple the length habitual. This implies that the protein encoded by this gene has an altered structure, altering the normal function of motor neurons of the brain and spinal cord, probably due to its intracellular accumulation. The affected neurons die, and lead to muscle weakness and atrophy. Individuals with the highest number of CAG repeats tend to develop more signs and symptoms early.

This process has a recessive X - linked, meaning that the mutated AR gene is on the X chromosome in males, who have only one X chromosome, this chromosome altered in all cells, is sufficient to express the disease . In females, having two X chromosomes, the mutation must be present on both chromosomes for the process is revealed. Therefore, the process is more common in men than in women. However, some women with one copy of the X chromosome altered, may exhibit signs and symptoms mild.

In addition, the spinobulbar muscular atrophy, other mutations in this gene are responsible for androgen insensitivity syndrome (Androgen Insensitivity Syndrome), or androgenic alopecia (androgenetic alopecia), and has also been implicated in the development of breast cancer , prostate cancer, and even endometrial carcinoma.

Tests performed in IVAMI: in IVAMI perform detection of CAG repeat associated conatrofia spinobulbar Kennedy, by complete PCR amplification of the AR gene, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).