Motor neuron disease: the C9orf72 hexanucleotide repeat expansion in FTD and ALS.

Two new studies provide strong evidence for the link between mutations in the C9orf72 gene and familial frontotemporal dementia or amyotrophic lateral sclerosis. One of the papers presents some unique associations between clinical features and C9orf72 mutation, and raises questions regarding the specificity of some previously reported pathological findings.