The nature and location of the amyloid typically reflects the disease, such that Parkinson’s is accompanied by amyloid forms of α-synuclein in the substantia nigra pars compacta8–10, Alzheimer’s by fibrillar forms of Aβ1-40/42 in many parts of the brain11–13, and type 2 diabetes – a disease with few genome-wide associations14 – by amylin fibrils in the insulin-producing cells of the pancreas15–25. The gene discussed is IAPP; the disease is type 2 diabetes mellitus.