Alexander Disease essay
Myelin is essentially made up of water proteins and mostly lipids, it covers the axons of all neurons in the form of a myelin sheath as it helps insulate the nerve fibers and promotes rapid transmission of nerve impulses. Myelin is produced by two different types of Glial cells, Oligodendrocytes produce myelin in the central nervous system (Brain and Spine) and Schwann cells produce myelin in the peripheral nervous system (Outside Brain and Spine).
If myelin is not properly maintained, the transmission of nerve impulses could be disrupted and as myelin deteriorates nervous system functions can be impaired. Alexander disease targets the CNS. Causes ALX is caused by a mutation in the GFAP (Glial fibrillary acidic protein) gene on chromosome 17. Molecules of this protein bind together to form intermediate filaments which are used to support and strengthen cells. The mutation causes a structural alteration in GFAP which impairs the formation of normal intermediate filaments and they collect in cells called astrocytes.
Astrocytes are non-neuronal glial cells that provide biochemical support to endothelial cells that form the blood-brain barrier, provide nutrients for nervous tissue and maintenance of extracellular ion balance etc. This leads to the formation of Rosenthal fibers in the astrocytes, abnormal clumps of GFAP. Therefore no nutrients are provided to the oligodendrocytes and as a result myelin is slowly degenerated. Symptoms Most cases of ALX begin before 2 years of age this is the infantile form and is the most common.
The mutation that causes ALX is spontaneous but if someone is suffering from the disorder and they have kids then the mutation can be inherited in an autosomal dominant manner, where one copy of the altered gene in each cell is sufficient to cause the disorder. Alexander disease has different stages the rarest being the neonatal form which occurs within a month of life and is associated with severe intellectual disability and developmental delay, buildup of fluid in the brain (hydrocephalus) and seizures.
The infantile form includes mental and physical developmental delay with increase in head and brain size, seizures, stiffness in the arms and/or legs (spasticity) and intellectual disability. The juvenile and adult form of the disease is less common and have mental and physical effects including speech abnormalities, swallowing difficulty, seizures, poor coordination (ataxia), dysarthria and excessive vomiting. ALX occurs in both females and males in all races of the human population.
Treatment There is no known permanent treatment to ALX but it can be managed to be more comfortable and reduce suffering. One must attend to general care like being in a comfortable position and having assistance for your needs. Nutritional requirements should be met that is eating a balanced diet in order to maintain health. Antibiotics should be given for any intercurrent infections and anti-epileptic drugs should be given for control of seizures.
The patient should begin speech therapy to help them overcome speaking difficulty, also physical and occupational therapy to overcome difficulty in movement. Finally genetic counseling should be offered to the family to provide them with information on the disease and how it should be managed in a home environment, it also keeps the family informed if there are any new treatments for the disease and any questions of importance can be answered. A bone marrow transplant was attempted on a child but proved unsuccessful as the child’s condition did not improve. Current Research
Research is aimed at understanding the mechanisms of the mutations that cause the disease and to screen FDA approved drugs for beneficial effects and to counter effect the symptoms of the disease. A lot of effort is devoted to identifying biomarkers in blood and cerebrospinal fluid to allow monitoring severity or progression of the disease and therefore provide the much needed foundation for future clinical trials. Ceftriaxone is one of the drugs that has just been cleared as FDA approved. In clinical trials a 2 gram intravenous dose was given to patients for 15 days monthly over a period of 4 years.
Over this span of time ataxia and dysarthria in patients improved from severe to mild on clinical rating scales. Palatal myoclonus (spasm of roof of mouth) was undetectable. Generally patients stated they had a better quality of life. Vigabatrin is an anticonvulsant drug that is under research at the moment. It is used in the treatment of seizures and west syndrome (a form of epilepsy), however one of the major side effects is encephalopathy including dementia and memory loss. ALX still has many under researched areas which can help people overcome ALX.