Congenital syphilis. Soles of a baby's feet showing characteristic skin peeling (desquamation) due to syphilis. Syphilis is caused by the bacterium Treponema pallidum, the congenital form is passed from mother to child during pregnancy (in utero). Congenital syphilis is now rare in the developed world as pregnant women are routinely screened. Desquamation is an early stage symptom of syphilis and treatment (for all stages) is with penicillin.