Fifteen of the patients provided written consent to genotype mutations in SOD1 and hexanucleotide expansions in C9orf72. We did not identify any missense mutations in SOD1 but, despite the lack of a family history of ALS [27], found four patients with a Southern blot confirmed hexanucleotide repeat expansions of 1700 or more repeats in C9orf72. This is an unexpectedly high representation of 24% in the genotyped subpopulation. Here, C9orf72 is linked to amyotrophic lateral sclerosis.