SYPHILIS
SYPHILIS ICD-10: A50-53
• Chronic systemic infection caused by the spirochete Treponema pallidum, transmitted through skin and mucosa, with manifestations in nearly every organ system.
• Incidence is ~6 million new cases annually worldwide in persons aged 15–49, and over 100,000 cases annually in the United States.
• Primary infection: A painless ulcer or chancre on the mucocutaneous site of inoculation. Associated with regional lymphadenopathy (chancriform syndrome: distal ulcer associated with proximal lymphadenopathy).
• Systemic infection: Shortly after inoculation, syphilis becomes a systemic infection with characteristic secondary and tertiary stages.
• Course: Clinical course and response to standard therapy may be altered in HIV/ AIDS.
ETIOLOGY AND EPIDEMIOLOGY
ETIOLOGY Venereal syphilis caused by Treponema pallidum. T. pallidum is a thin delicate spirochete with 6 to 14 spirals. Only natural host for T. pallidum is the human. Subspecies of T. pallidum cause the nonvenereal diseases endemic syphilis (bejel), yaws, and pinta. TRANSMISSION Sexual contact: Contact with infectious lesion (chancre, mucous patch, condyloma latum, and cutaneous lesions of secondary syphilis). Sixty percent of those in contact with persons having primary and secondary syphilis become infected. Congenital infection: In utero or perinatal transmission. PATHOGENESIS The spirochetes pass through an intact mucous membrane and microscopic abrasion in skin, enter lymphatics and blood within a few hours, and produce systemic infection and metastatic foci before
development of a primary lesion. Spirochetes divide locally, with resulting host inflammatory response and chancre formation, either a single lesion or, less commonly, multiple lesions. Cellular immunity is of major importance in healing of early lesions and control of infection (TH1 type). Primary syphilis is the most contagious stage of the disease. Later syphilis is essentially a vascular disease, lesions occurring secondary to obliterative endarteritis of terminal arterioles and small arteries, and by the resulting inflammatory and necrotic changes.
LABORATORY EXAMINATIONS
DARK-FIELD MICROSCOPY Positive in primary chancre and papular lesions of secondary syphilis such as condylomata lata. Unreliable in oral cavity because of the presence of saprophytic spirochetes, and negative in patients treated systemically or topically with
antibiotics. Regional lymph node aspirated and aspirate examined in the dark-field microscope. Direct Fluorescent Antibody T. pallidum (DFA-TP) Test. Fluorescent antibodies are used to detect T. pallidum in exudate from lesion, lymph node aspirate, or tissue. SEROLOGIC TESTS FOR SYPHILIS (STS) Positive in persons with any treponemal infection. Tests always positive in secondary syphilis. Nontreponemal serologic tests for syphilis (STS). Measures IgG and IgM directed against cardiolipin–lecithin–cholesterol antigen complex. Rapid plasma reagin (RPR) test (automated RPR: ART). VDRL slide test; nonreactive in 25% of patients with primary syphilis. In early syphilis: Either do the fluorescent treponemal antibody-absorbed (FTA-ABS) test or repeat VDRL in 1 to 2 weeks if the initial VDRL is negative. Prozone phenomenon: If antibody titer high, test may be negative; must dilute serum; becomes nonreactive or reactive in lower titers following therapy for early syphilis. Treponemal STS Fluorescent treponemal antibody test absorption (FTA-ABS) test. Agglutination assays for antibodies to T. pallidum: Microhemagglutination assay (MHA- TP; Serodia TPPA test); T. pallidum hemagglutination test (TPHA). Often remain reactive after therapy; not helpful in determining infectious status of patient with past syphilis. DERMATOPATHOLOGY In primary and secondary syphilis, lesional skin biopsy shows central thinning or ulceration of epidermis. Lymphocytic and plasmacytic dermal
infiltrate. Proliferation of capillaries and lymphatics with endarteritis; may have thrombosis and small areas of necrosis. Dieterle (silver) stain demonstrates spirochetes.
COURSE
Even without treatment, chancre heals completely in 4 to 6 weeks. The infection either becomes latent or clinical manifestations of secondary syphilis appear. Secondary syphilis usually manifests as macular exanthem initially; after weeks, lesions resolve spontaneously and recur as maculopapular or papular eruptions. In 20% of untreated cases, up to three to four such recurrences followed by periods of clinical remission may occur over a period of 1 year. Infection then enters a latent stage, in which there are no clinical signs or symptoms of the disease. After untreated syphilis has persisted for >4 years, it is rarely communicable, except in the case of pregnant women, who, if untreated, may transmit syphilis to their fetuses, regardless of the duration of their disease. One-third of patients with untreated latent syphilis developed clinically apparent tertiary disease. Gummas hardly ever heal spontaneously. Noduloulcerative syphilides undergo spontaneous partial healing, but new lesions appear at the periphery.
TREATMENT
Antibiotics (see p. 809 for specific doses). Educate patients and treat sex partners. In the United States, report cases to the Department of Health.