<prompt> A man presents to a dermatologist because of a severe mucocutaneous rash that involves most of his body,including his palms and soles. Questioning reveals that he is a merchant marine who several months previously had an encounter with a prostitute in Southeast Asia. Which of the following is the most likely causative agent of this rash?Herpes simplex IHerpes simplex IIHIVTreponema pallidum  <response>: The rash described is that of secondary syphilis, caused by Treponema pallidum. Involvement of palms and soles by a rash is unusual, and secondary syphilis should come to mind. Not all patients with secondary syphilis have a severe form of the rash, and consequently some cases are missed. Primary syphilis takes the form of a painless, button-like mass called chancres. Teiary syphilis, which is now rare, has a propensity for involving the aoa and central nervous system and can also cause gummas granulomatous-like lesions in many sites, notably including liver and bone. Herpes simplex I usually causes perioral Herpes simplex II usually causes genital vesicular lesions. HIV does not itself cause a rash, although coinfection with other organisms can result in a rash. Ref: Ray C.G., Ryan K.J. 2010. Chapter 37. Spirochetes. In C.G. Ray, K.J. Ryan Eds, Sherris Medical Microbiology, 5e. 