In one study, CST3 was shown to be decreased in frontotemporal dementia with GRN mutation compared to C9orf72 repeat expansion carriers, suggesting that it may differentiate frontotemporal dementia subtypes.116 However, CST3 levels were also significantly lower in both CSF and serum in Alzheimer’s disease and dementia with Lewy bodies.117 Further research is needed to establish the use of CST3 as a biomarker for amyotrophic lateral sclerosis or frontotemporal dementia. The gene discussed is GRN; the disease is frontotemporal dementia.