The difficulties in the diagnosis of syphilis have been admitted by the most skillful diagnosticians. The reason for this is that the cutaneous manifestations of syphilis may be imitated by quite a number of other less obnoxious skin diseases and that syphilis may often appear in forms which simulate the lesions of other dermatoses. As Dr. White says, the skin, by its comparatively simple structure, is incapable of displaying a large variety of pathologic manifestations, and the limited number of skin lesions are therefore reappearing in a large number of morbid conditions.
No less an authority than Kaposi says:
The syphilids do not offer any other morphologic properties than the non-syphilitic dermatoses, as they all appear in macules, papules, pustules with secondary formation of scales and crusts. Their unquestioned specific clinical features, by which they can be distinguished from all other non-syphilitic dermatoses, and which impress us as peculiar typical
FISCHKIN EA. THE ELEMENTS OF DIAGNOSIS OF CUTANEOUS SYPHILIS.. JAMA. 1905;XLV(2):95-98. doi:10.1001/jama.1905.52510020015002c