Amyotrophic lateral sclerosis type 6 is an inherited disorder involving progressive degeneration of motor neurons which results in muscle weakness and atrophy. Type 6 is caused by a defect on chromosome 16 in FUS gene. Type 6 is characterized adult onset of symptoms with progression varying between 1 and 20 years. It occurs in an autosomal dominant pattern of inheritance.
Initial symptoms depend on which first muscles are affected.
- Muscle weakness
- Loss of motor control in hands and arms
- Difficulty speaking
- Difficulty swallowing
- Difficulty breathing
- Persistent fatigue
- Muscle twitching
- Exaggerated reflexes
- Muscle cramps
- Weak hand muscles
- Wasting of hand muscles
- Weak forearm muscles
- Wasting of forearm muscles
- Weak leg muscles
- Wasting of leg muscles
- Weak body muscles
- Wasting of body muscles
- Weak face muscles
- Wasting of face muscles
- Progressive muscle weakness
- Progressive muscle wasting
- Progressive paralysis
The exact cause of ALS is unknown, but about 5 to 10% of cases have a genetic component.
In patients with ALS type 6, mutations in FUS gene were found. FUS gene codes a protein called “fused in sarcoma” (FUS). This protein is involved in many steps of protein production in the cells. It regulates transcription, which is the first step in the production of proteins from genes; helps repair mistakes in DNA, which prevents cells from accumulating genetic damage and has other important functions.
At least 50 mutations in the FUS gene have been found to cause ALS. These defects caused malfunction of FUS protein in the cells.
It is unclear why some people with FUS gene mutations develop frontotemporal dementia (FTD) and others do not. Individuals who develop both conditions are diagnosed as having ALS-FTD.
ALS6 has an autosomal dominant trait. Autosomal dominant is one of several ways that a trait or disorder can be passed down through families. If a disease is autosomal dominant, it means you only need to get the abnormal gene from one parent in order for you to inherit the disease. One of the parents may often have the disease.
A genetic counselor is helpful to diagnosis ALS6 if there is family history of ALS.
The diagnosis of ALS is primarily based on the symptoms and signs observes in a patient as well as a series of tests to rule out other diseases.
Following exam will be helpful to diagnosis the ALS6
- Weakness, often beginning in one area
- Muscle tremors, spasms, twitching, or loss of muscle tissue
- Twitching of the tongue (common)
- Abnormal reflexes
- Stiff or clumsy walk
- Increased reflexes at the joints
- Difficulty controlling crying or laughing (sometimes called emotional incontinence)
- Loss of gag reflex
- Tests that may be done include:
- Blood tests to rule out other conditions
- Breathing test to see if lung muscles are affected
- Cervical spine CT or MRI to be sure there is no disease or injury to the neck, which can mimic ALS
- Electromyography to see which nerves or muscles do not work properly
- Genetic testing, if there is a family history of ALS
- Head CT or MRI to rule out other conditions
- Swallowing studies
- Spinal tap (lumbar puncture)
Genetic testing is recommended, if there is a family history of ALS and some of the described symptoms occur.
Regardless of the part of the body first affected with the disease, muscle weakness and atrophy spread to other parts of the body and eventually of the respiratory. Although ventilation support can ease problems with breathing and prolong survival, it does not affect the progression of ALS. Most people with ALS die from respiratory failure within 3 to 5 years from the onset of symptoms. About 25 percent of patients live more than 5 years after diagnosis.
There is no known cure for ALS.
A medicine called Riluzole helps to slow down the symptoms and lets you live longer. The drug also may delay the need for a tracheostomy (breathing tube).
Treatments to control other symptoms include:
- Baclofen or diazepam for spasticity that interferes with daily activities
- Trihexyphenidyl or amitriptyline for people with problems swallowing their own saliva
Physical therapy, occupational therapy, and rehabilitation may help to prevent joint immobility and slow muscle weakness and atrophy.
Drugs are available to help individuals with pain, panic attacks, and depression
Patients with ALS tend to lose weight. The illness itself increases the need for food and calories. At the same time, problems with swallowing (resulting in chocking) make it hard to eat enough. Researchers have stated that ALS patients have a chronically deficient intake of energy and recommended augmentation of energy intake and encourage patients not to restrict their calorie intake. Patients may decide to use a gastrostomy (a surgical opening into the stomach for nutritional support through a tube).
Due to increasing problems with breathing, individuals with ALS may eventually consider forms of mechanical ventilation (respirators).
- Amyotrophic lateral sclerosis
- Genetic Home Reference
- National Institute of Neurological Disorders and Stroke
- Medline Plus
- PubMed Health