'Shrouded in a dark fog': comparison of the diagnosis of pellagra in Venice and general paralysis of the insane in the United Kingdom, 1840-1900.

The debate on the causes and the nature of pellagra in Italy during the nineteenth century resembles and evokes the similar debate on General Paralysis of the Insane (GPI) that was growing at the same time in the United Kingdom. Pellagra and GPI had a massive and virulent impact on the populations of Italy and the UK, respectively, and contributed to a great extent to the increase and overcrowding of the asylum populations in these countries. This article compares the two illnesses by examining the features of their nosographic positioning, aetiology and pathogenesis. It also documents how doctors arrived at the diagnoses of the two diseases and how this affected their treatment.