Overview Of Alexander’s Disease
Alexander’s disease is a rare nervous system disorder that involves the deterioration of the myelin within a person’s brain. This disorder is one of a group of disorders (leukodystrophies) involving the destruction of myelin. Myelin, a fatty substance, normally covers and insulates nerve fibers within the brain to help promote the proper transmission of nerve impulses. Damaged or destroyed myelin will disrupt or impair nerve signal transmission. As the brain’s myelin is damaged/deteriorates during diseases such as Alexander’s disease and other leukodystrophies, the person’s nervous system won’t function like it should.
Symptoms of Alexander’s Disease
Most of the time, Alexander’s disease begins to show signs before the age of two. Symptoms of the disorder at this time in a child’s life can include an enlarged head size/brain size (megalencephaly), stiffness in the legs and/or arms, developmental delays, seizures, and intellectual disability.
Less frequently, the disease onsets later on into childhood, or perhaps even into adulthood. Symptoms for this onset period can include seizures, swallowing difficulties, ataxia (poor coordination), and difficulties with speech.
In rare cases, Alexander’s disease can occur before the first month of life. This version of the disease has symptoms that can include a severe developmental delay, severe intellectual disability, hydrocephalus (a fluid build-up in the brain), and seizures.
Commonly Associated With
Dysmyelinogenic leukodystrophy, Leukodystrophy with Rosenthal fibers, AxD, Demyelinogenic leukodystrophy, ALX, and Fibrinoid degeneration of astrocytes
Causes Of Alexander’s Disease
Scientists don’t fully understand what exact mechanism causes Alexander’s disease. They do know that mutations within a gene called GFAP are essential to the development of the disease. The GFAP gene normally provides the necessary instructions for the production of a protein called the glial fibrillary acidic protein. When these proteins bind together, they form something called intermediate filaments. These provide necessary strength and support to nerve cells. A mutated GFAP gene prevents the proper formation of those proteins. This means the filaments don’t form normally. These abnormal proteins are instead thought to collect and accumulate in astroglial cells (these interact with synapses). This eventually leads to the formation of fibers called Rosenthal fibers, which can impair cell function. It’s still unknown how exactly that process relates to the deterioration of myelin.
Alexander’s disease has an unknown prevalence. Only 500 reported cases exist worldwide since the disorder was first discovered and named in 1949.