Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with a prevalence of 5.4/100 000 (Chiò et al., 2013). Although most cases are sporadic, 10% of patients have a positive family history. Pathogenic variants in genes C9orf72, SOD1, TARDBP, and FUS explain almost two thirds of the familial forms (>25%, 20%, 5%, and 5% respectively). Only one genetic alteration has been identified in the C9orf72 gene. It consists of a GGGGCC hexanucleotide expansion, which is not detectable by next-generation-sequencing.
Primary lateral sclerosis (PLS) is characterized by the isolated involvement of the upper motor neuron, which distinguishes it from amyotrophic lateral sclerosis, in which involvement of the lower motor neuron also occurs. The diagnosis of PLS is reached by excluding other causes of disease such as spastic paraplegia, multiple sclerosis, metabolic disease, or myelopathy.
| ALS1 | ALS2 | ALS4 | ALS5 | ALS6 | ALS8 | ALS9 | ALS10 | ALS11 | ALS12 | ALS14 | ALS15 | ALS16 | ALS17 | ALS18 | ALS19 | ALS20 | ALS21 | FTDALS2 | FTDALS3 | FTDALS4 |