C9ORF72 hexanucleotide repeat expansions in the Italian sporadic ALS population

It has been recently reported that a large proportion of patients with familial amyotrophic lateral sclerosis (familial ALS) and frontotemporal dementia (FTD) are associated with a hexanucleotide (GGGGCC) repeat expansion in the first intron of C9ORF72. We have assessed 1,757 Italian sporadic ALS cases, 133 from Sardinia, 101 from Sicily, and 1,523 from mainland Italy. Sixty (3.7%) of 1,624 mainland Italians and Sicilians and 9 (6.8%) of the 133 Sardinian sporadic ALS cases carried the pathogenic repeat expansion. None of the 619 regionally-matched control samples (1,238 chromosomes) carried the expansion. Twenty-five cases (36.2%) had behavioral FTD in addition to ALS. FTD or unspecified dementia was also detected in 19 pedigrees (27.5%) in first-degree relatives of ALS patients. Cases carrying the C9ORF72 hexanucleotide expansion survived one year less than cases who did not carry this mutation. In conclusion, we found that C9ORF72 hexanucloetide repeat expansions represents a sizeable proportion of apparent sporadic ALS in the Italian and Sardinian population, representing by far the commonest mutation in Italy and the second more common in Sardinia.