Furthermore, Bulgarian patients with FTD-ALS were more likely to carry a C9orf72 repeat expansion (1/7, 14%), similar to the increased risk (33%-86%) of harbouring a C9orf72 repeat expansion in patients with concurrent ALS and FTD or with a family history of dementia or ALS reported in the literature [14]. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.