[Psoriasis and leprosy in the light of common history. A contribution on epidemiology and differential diagnosis].

Over the centuries psoriasis was described as a variety of leprosy. It is only in the last century, however, that it was described as a separate entity. Many early medical descriptions of this woridwide affliction can be found, which attempt to distinguish between the various kinds of leprosy. These attempts led to cultural-religious consequences on one hand and to different theories about their contagiousness and curability on the other. Today the current conviction, that with the proof for the existence of a lepra bacillus the question of heritability of the disease can finally be discarded, is being reconsidered. For both psoriasis and leprosy the search for relationships between these diseases and genetically determined markers in the blood-, serum protein- and enzyme-group systems has led to applicable results which, insofar as they can be interpreted as indications of selective factors, will enable us to understand the geographical distribution of both diseases.