Alexander disease is a rare and fatal neurological disorder that is mainly found in infants and children. This neurodegenerative disease is caused due to defect in a type of gene that encodes a protein called GFAP (glial fibrillary acidic protein). Alexander disease is grouped under degenerative nervous cell disorder called leukodystrophies.
This disease is characterized by destruction of myelin sheath (white matter) that protects the nerve fibers in the brain.It is accompanied with formation of abnormal fibers called Rosenthal fibers in specific cells of brain called astrocytes.
The disease is divided into three forms, according to the age of onset; infantile, juvenile and adult. Adult form is the rarest of all. The symptom may vary from one age group to another. There is no cure of Alexander disease. Treatment is symptomatic and supportive.
Types And Symptoms Of Alexander Disease
The symptoms may vary according to the three forms that are infantile, juvenile and adult. But sometime there is no clear cut demarcation of symptoms and they may overlap one another disregarding the age group. The disease most often develops during infantile stage that is in first 2 years of life.
Onset of juvenile form is between 2 to 13 years of life. Alexander disease in adults is very less. The disease occurs in both males and females, without any specific ethnic and cultural difference.
Infantile Alexander disease symptoms:
It begins in first two years. Some children die in first year of life and some survive for 5 years or more. The symptoms are progressive leading to mental and developmental delays. There may be spasticity of all four limbs.
- Abnormally large head
- Water in brain
- Developmental delays
- Delayed physical growth
- Stiffness on leg and hand muscles which causes difficulty in walking, standing and sitting.
Symptoms of juvenile Alexander disease:
The age of onset is between 4 and 10 in general.
- Difficulty in swallowing due to affection of muscles of deglutition.
- Excessive vomiting
- Slurred speech
- Loss of motor control
- Poor coordination
- Inability to cough
- Slow decline in mental function.
Adult Alexander disease Symptoms:
It is rare of all the forms. The onset can be from late teen years to very late in life.
- Difficulty in coordination.
- Difficulty in articulation of speech.
- Difficulty in swallowing.
- Insomnia and sleep apnea.
- Difficulty in walking.
- Weakness in one side of body.
The symptoms of adult form may sometime appear similar to multiple sclerosis or Parkinson’s disease.
What Causes Alexander Disease?
Research suggests that Alexander disease is caused due to mutation in the gene that is responsible for formation of glial fibrillary acidic protein (GFAP). This protein is involved in making of cells of central nervous system.
The disease does not have any genetic inheritance. This means the genetic defect does not come from the parents and is sporadic and sudden in the patient. It also means that if one child has Alexander disease, it is not necessary that others will have it. However, in some cases familial trait is observed, especially in adult variety. Disease can occur at any age and in all races.
In Alexander disease, there is degeneration of white matter or the myelin sheath due to defect in GFAP. There are two types of brain cells, the neurons and glial cells. Neurons are meant to transmit electric signals all over the body. Glial cells in brain support neuron in their function. In Alexander disease a special type of glail cells called astrocytes have abnormal structure called Rosenthal fibers. These fibers are not present in the cells of normal healthy person. Their presence is responsible for degeneration of myelin sheath.
Diagnosis And Treatment For Alexander Disease
Alexander disease can be diagnosed with genetic blood test as the genetic defect is known. Even clinical appearance of large head and other symptoms may help to diagnose the condition.
Alexander disease is not curable and patient suffering from it dies sooner or later. The treatment is only supportive. For example fluid collection in brain can be treated surgically. A shunt can be placed to drain excess of fluid which may responsible for increased intra cranial pressure.
Proper nutrition should be maintained. Medicines may be needed to control seizures. Speech therapy and occupational therapy are undertaken to improve disabilities in learning and speaking.