Amyotrophic lateral sclerosis, or ALS, is a disease that causes motor neurons in the brain and spinal cord to decay over time. Motor neurons are in charge of muscle movement throughout the body. As ALS progresses, these motor neurons begin to die, causing the brain to lose its ability to control and initiate muscle movement. Those affected by ALS lose their ability to move their muscle voluntarily, affecting their ability to speak, eat, move, and breathe.
ALS is the most common motor neuron disease, mainly affecting adults between the ages of 40 and 60, with men being one-and-a-half times more likely to have the disease than women.
ALS can be grouped in different ways. Most commonly used are two classifications based on the underlying cause of the disease, either sporadic (the most common form) or familial. Sometimes ALS is also classified by the clinical onset or progression of the disease.
About 10 percent of cases are classified as hereditary or Familial ALS (fALS). Although clinically indistinguishable from Sporadic ALS, Familial ALS or fALS is inherited through an autosomal dominant gene mutation. When we are born, we get one copy of DNA from each parent, but normally only one of these genes expresses itself. The expressed gene is considered the more dominant gene. An autosomal dominant gene is the gene that will always be expressed in a carrying individual. There are several different genes that have been associated with fALS. The first discovered gene is SOD1, which comprises 12 percent of fALS cases. Because there are so many different genes, most cases are not tested for fALS unless there is known history of the disease in the patient's family.