This image shows the condition syphilitic rupia with keloid scarring present on the arm. Syphilitic rupia is a bacterial skin infection which causes a pustular eruption of encrusted ulcers on this skin. In this case healed ulcers have formed keloid scars (red and raised scars). The appearance of the sometimes yellow pus-filled ulcer has been likened to oyster shells. This kind of skin manifestation is common in late, recurrent secondary syphilis. Chromolithograph, 1878-1888. Illustration by E. Burgess after R. W. Sherwin, Mabel Green and Jonathan Hutchinson.