Most notably, single neuron qPCR for APP combined with PNA‐FISH for proximal and distal APP exons identified increased APP copy numbers of up to 12 copies, arising somatically and mosaically in sporadic AD neurons (Bushman et al., 2015): CNV increases of just 3 APP copies is pathogenic for AD in Down syndrome (via trisomy 21 on which APP resides) (Wiseman et al., 2015) and rare familial cases of APP locus duplication (Hooli et al., 2012). The gene discussed is APP; the disease is Alzheimer disease.