Stage	Clinical manifestations	Diagnosis (sensitivity)	Treatment
Primary syphilis	Chancre	Dark-field microscopy of skin lesion (80%) Nontreponemal tests (78% to 86%) Treponemal-specific tests (76% to 84%)	Penicillin G benzathine, 2.4 million units IM (single dose) Alternatives in nonpregnant patients with penicillin allergy: doxycycline (Vibramycin), 100 mg orally twice daily for 2 weeks; tetracycline, 500 mg orally four times daily for 2 weeks; ceftriaxone (Rocephin), 1 g once daily IM or IV for 8 to 10 days; or azithromycin (Zithromax), 2 g orally (single dose)
Secondary syphilis	Skin and mucous membranes: diffuse rash, condyloma latum, other lesions Renal system: glomerulonephritis, nephrotic syndrome Liver: hepatitis Central nervous system: headache, meningismus, cranial neuropathy, iritis and uveitis Constitutional symptoms: fever, malaise, generalized lymphadenopathy, arthralgias, weight loss, others	Dark-field microscopy of skin lesion (80%) Nontreponemal tests (100%) Treponemal-specific tests (100%)	Same treatments as for primary syphilis
Latent syphilis	None	Nontreponemal tests (95% to 100%) Treponemal-specific tests (97% to 100%)	Early latent syphilis: same treatments as for primary and secondary syphilis Late latent syphilis: penicillin G benzathine, 2.4 million units IM once weekly for 3 weeks Alternatives in nonpregnant patients with penicillin allergy: doxycycline, 100 mg orally twice daily for 4 weeks; or tetracycline, 500 mg orally four times daily for 4 weeks
Tertiary (late) syphilis	Gummatous disease, cardiovascular disease	Nontreponemal tests (71% to 73%) Treponemal-specific tests (94% to 96%)	Same treatment as for late latent syphilis
Neurosyphilis	Seizures, ataxia, aphasia, paresis, hyperreflexia, personality changes, cognitive disturbance, visual changes, hearing loss, neuropathy, loss of bowel or bladder function, others	Cerebrospinal fluid examination	Aqueous crystalline penicillin G, 3 to 4 million units IV every 4 hours for 10 to 14 days; or penicillin G procaine, 2.4 million units IM once daily, plus probenecid, 500 mg orally four times daily, with both drugs given for 10 to 14 days