We have previously reported the whole genome genotyping analysis of 2 consanguineous siblings
clinically diagnosed with early onset Alzheimer’s disease (AD). In this analysis, we identified several large
regions of homozygosity shared between both affected siblings, which we suggested could be candidate
loci for a recessive genetic lesion underlying the early onset AD in these cases. We have now performed
exome sequencing in one of these siblings and identified the potential cause of disease: the CTSF
c.1243G>A:p.Gly415Arg mutation in homozygosity. Biallelic mutations in this gene have been shown to
cause Type B Kufs disease, an adult-onset neuronal ceroid lipofuscinosis with some cases resembling the
impairment seen in AD.