Syphilis is caused by T. pallidum, a long, slender, coiled spirochete. It cannot be cultivated routinely in vitro but can be observed by dark-field microscopy. Untreated infectionprogresses through several clinical stages (see Table 116-2). Primary syphilis is manifested as a single, painless genital ulcer, or chancre, usually on the genitalia, that appears 3 to 6 weeks after inoculation. Secondary syphilis follows 6 to 8 weeks later and is manifested as fever, generalized lymphadenopathy, and a disseminated maculopapular rash that alsois present on the palms and soles. Plaquelike skin lesions,condylomata lata, and mucous membrane lesions occur and are infectious. Tertiary syphilis is a slowly progressivedisease that involves the cardiovascular, neurologic, andmusculoskeletal systems and is not seen in children. Latent syphilis is an asymptomatic infection detected by serologictesting. Early latent syphilis indicates acquisition within thepreceding year; all other cases of latent syphilis are designated either late latent syphilis or latent syphilis of unknownduration. Infection can be passed from pregnant women and infect their infants resulting in congenital syphilis (see Chapter 66).
The diagnosis of syphilis is based on serologic testing. Nontreponemal antibody tests, the Venereal Disease Research Laboratory (VDRL) test, and the rapid plasma reagin (RPR)test are screening tests and can be quantified as titers that increase with increasing duration of infection and decrease in response to therapy. A nonquantitative VDRL test can be performed on cerebrospinal fluid but is insensitive. Rheumatic disease and other infectious diseases may cause false positive results. Confirmatory, specific treponemal antibody tests, the microhemagglutination assay-T. pallidum (MHA-TP) and fluorescent treponemal antibody-absorption (FTA-ABS) are more specific and are used to confirm the diagnosis of syphilis. These tests usually remain positive lifelong even if the infection is treated and cured. Dark-field examination of chancres, mucous membranes, or cutaneous lesions may reveal motile organisms.
The treatment of choice for all stages of syphilis is parenteral penicillin G. Primary syphilis, secondary syphilis, and early latent syphilis are treated with a single IM dose of benzathine penicillin G. Tertiary, late latent, and latent syphilis of unknown duration are treated with three doses at 1-week intervals. Neurosyphilis is treated with intravenous aqueous crystalline penicillin G for 10 to 14 days. A systemic, febrile Jarisch-Herxheimer reaction occurs in 15% to 20% of syphilitic patients treated with penicillin.
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HSV-1 and HSV-2 are large, double-stranded DNA viruses of the herpesvirus family with a linear genome contained within an icosahedral capsid. There is significant DNA homology between types 1 and 2. The virus initially infects mucosal surfaces and enters cutaneous neurons where it migrates along the axons to sensory ganglia. As viral replication occurs in the ganglia, infectious virus moves along the axon to infect and destroy epithelial cells. Infection may disseminate to other organs in immunocompromised patients. Virus latency is maintained in the ganglia where it undergoes periodic reactivation and replication triggered by undefined events. Although either virus can be found in any site, HSV-1 more commonly occurs in the central nervous system, eyes, and mouth, whereas HSV-2 more commonly involves the genitalia. Reinfection can occur with exposure to the other type or even a second strain of the same type.