‘Progressive lenticular degeneration may be defined as a disease which occurs in young people, which is often familial but not congenital or hereditary; it is essentially and chiefly a disease of the extrapyramidal motor system, and is characterised by involuntary movements, usually of the nature of tremor, dysarthria, dysphagia, muscular weakness, spasticity, and contractures with progressive emaciation; with these may be associated emotionalism and certain symptoms of a mental nature. It is progressive, and, after a longer or shorter period, fatal. Pathologically it is characterised predominantly by bilateral degeneration of the lenticular nucleus, and in addition cirrhosis of the liver is constantly found, the latter morbid condition rarely, if ever, giving rise to symptoms during the life of the patient.’This proposed definition appears midway through Samuel Alexander Kinnier Wilson’s original and magisterial account of progressive lenticular degeneration. In publishing part of his thesis, submitted for the degree of MD at the University of Edinburgh in July 1911 for which a gold medal was awarded, Dr Kinnier Wilson has written, at 214 printed pages, the longest paper ever published in Brain. His aim is to describe, for the first time so far as he can ascertain, a disorder that is often familial, affects young people, and is invariably fatal. Dr Kinnier Wilson has encountered four cases (two of whom were siblings), making the diagnosis during life in three; but he acknowledges that the literature may contain six previous reports and he has located the case notes of two other affected individuals, previously not described, from these same families.