Recent studies have provided some insight for the possible causes of the familial type of amyotrophic lateral sclerosis (FALS). This disease occurs only in 10% of the known cases of ALS with the sporadic, non-hereditary form being predominant [7, 9]. ALS in general has an occurrence of 0.4 to 1.8 per 100,000 live births . ALS has been called Lou Gehrig’s disease, Charcot’s disease and motor neuron disease in other literature . ALS is a neurodegenerative disease of upper and lower motor neurons that can manifest in such a way that it can be misdiagnosed. Such areas include respiratory muscles with initial diagnosis of asthma, or even psychological problems that appear as a dementia . The primary manifestations are not restricted to any certain area of the body. FALS is inherited autosomally as a dominant trait [9,12,13,17]. It exhibits heterogeneity and may not be present in a consecutive generation . It is diagnosed usually near the age of fifty and ranges from 20-72 years [9,17]. Most patients are given a prognosis of 5 years of life after diagnosis . It has also been proposed that the juvenile form may be recessive. There is a predominance of maternal transmission in later onset and paternal transmission in early onset .
The bulk of this paper will deal with the SOD1 gene mutations as the proposed cause for some types of FALS. Many other hypothesis have been developed and will be briefly addressed at this point. Autoimmune disease and mutations in the glutamate receptor are other proposed causes.
Autoimmune disease has been studied as a possible agent for the cause of FALS . Supportive evidence includes the deficiency of IgG1 or IgG3 or both in 16/25 observed patients; subclass deficiency could be occurring in some patients who were not included in the group of 16. In the clinical setting total IgG is most often measured and this may obscure an underlying subclass deficiency .
Mutations in the glutamate receptors have also been studied. Glutamate is known to be a powerful neurotoxin . The GluR5 gene, located on chromosome 21, codes for the glutamine receptor N--Methyl D-Aspartate (NMDA) which is also located near the locus for the familial form of ALS. This includes it as a possible causative agent for ALS, as well [3,5,6]. Clear delineation’s between motor neuron disease, Parkinson’s disease and dementia are hard to make . The definition of ALS includes degeneration of upper and lower motor neurons. Sometimes dementia may be the result of ALS and this may be misdiagnosed.
FALS is considered an autosomal dominantly inherited trait. Due to the rare occurrence, few twin studies have been made; however, there has been a set of identical twins found in which one was diagnosed with ALS and the other was not . There can be a problem in reviewing FALS due to under-reporting and incomplete family histories. Family studies are as extensive as possible and even involve reviewing death certificates....