A 23-year-old male presented with a 3-week history of an asymptomatic erythematous, scaly rash on his trunk and face. A sore on his penis was seen during physical examination.

The patient reported having no travel history and had not started any new medications. He reported that no sexual contacts had similar lesions. The patient was afebrile and denied recent illnesses.

Diagnosis: Secondary Syphilis. Blood work revealed a positive RPR (rapid plasma reagin) test. A diffuse dermal infiltrate of plasma cells were seen on histologic examination of the skin, diagnostic for secondary syphilis.

Syphilis is caused by the bacteria Treponema pallidum. It can be congenital or sexually transmitted. The primary lesion, or chancre, is a well-circumscribed, firm, painless ulceration that usually occurs 3 weeks after exposure and lasts for a few weeks. The patient will also often have regional lymphadenopathy.

Secondary syphilis usually occurs 4-10 weeks after exposure. Patients may have flulike symptoms, generalized lymphadenopathy, and mucosal ulcers. The most common presentation is a papulosquamous rash, as seen in this patient. Other findings include condyloma lata, "moth eaten" alopecia, and perleche.

If secondary syphilis is left untreated, the disease may go into the latent stage, with resolving symptoms. About one-third of these patients will progress to tertiary syphilis. Patients may develop gummas in the skin, mucous membranes, or bones. Neurosyphilis or cardiovascular syphilis may occur.

Syphilis can be diagnosed by dark-field microscopy of spirochetes isolated from cutaneous lesions such as the chancre. The VDRL (Venereal Disease Research Laboratory) test and the RPR test detect antibodies to cardiolipin, and are positive in patients with active infection. However, the tests may be negative in very early infection, and the tests usually become negative with effective treatment. The FTA-ABS (fluorescent treponemal antibody absorption) test usually remains positive, indefinitely.

Penicillin is the treatment of choice for syphilis. If the patient is allergic, doxycycline, tetracycline, erythromycin, or ceftriaxone may be considered.

Dr. Martin is in private practice in Miami. More diagnostic cases are available at skinandallergynews.com. To submit your cases for possible publication, send an e-mail to sknews@elsevier.com.

This case was submitted by Dr. Adam Mamelak, of the department of dermatology at Johns Hopkins University, Baltimore.