Latent Syphilis

Latent syphilis is infection with Treponema pallidum shown by positive serology without signs or symptoms, after resolution of primary or secondary disease. Early latent syphilis is acquired within the past year; late latent is over 1 year or of unknown duration.

• Usually found on screening in pregnancy, blood donors, HIV clinics and at routine testing.
• Relapse to secondary lesions occurs in the first year in about 25 percent of untreated people.

No symptoms or signs.

• History of a chancre or rash may be recalled; prior negative test or a documented titre rise dates the infection.
• Examination should exclude tertiary signs: gummas, aortic regurgitation or aneurysm, neurological signs, uveitis and optic atrophy.
• Differential diagnosis: biological false positive non treponemal tests (pregnancy, autoimmune disease, malaria, tuberculosis, HIV, recent vaccination), previously treated syphilis (serofast), yaws, pinta and bejel (positive treponemal tests).
• Complications: late (tertiary) syphilis in about 15 to 40 percent of untreated people (cardiovascular, gummatous, neurosyphilis), congenital syphilis in pregnancy, ocular and otic syphilis, transmission before one year.

Reactive treponemal and non treponemal tests in a person with no signs of active infection.

• Confirm with a second treponemal test; quantify the RPR or VDRL titre; determine the stage by history of prior test, symptoms and partner infection.
• Examination of the cardiovascular system and the nervous system; visual acuity and fundoscopy; HIV test.
• CSF examination if neurological, ocular or otic features, treatment failure, or tertiary disease; chest radiograph or echocardiography when cardiovascular syphilis is suspected.

Treat to prevent late complications and congenital infection.

• Supportive: counselling, partner notification (partners of early latent disease within 90 days; long term partners and children in late latent disease), condoms, HIV and STI screening, vaccination for hepatitis B, explain that treatment prevents progression but does not reverse established damage.
• Pharmacological: early latent: benzathine benzylpenicillin 2.4 million units IM single dose. Late latent or unknown duration: benzathine benzylpenicillin 2.4 million units IM weekly for 3 weeks (total 7.2 million units); children 50,000 units/kg weekly for 3 weeks (maximum 2.4 million units per dose). Penicillin allergy (not pregnant): doxycycline 100 mg twice daily for 14 days (early) or 28 days (late). Jarisch Herxheimer reaction: paracetamol 1 g and fluids.
• Procedures: lumbar puncture when indicated.
• Special groups: pregnancy, penicillin only (desensitise if allergic) with the full schedule, keeping the interval between doses at 7 days and no longer than 9 days; HIV, give the three weekly doses and examine CSF if CD4 is 350 or less or the titre is 1 in 32 or more; children, evaluate for congenital syphilis.
• Red flags: neurological, visual or hearing symptoms, aortic signs, gummas, pregnancy, rising titre after treatment.
• Follow-up: RPR or VDRL at 6, 12 and 24 months; a fourfold fall within 12 to 24 months is expected; retreat and examine CSF for a fourfold rise or if titre fails to fall; a low titre serofast state is common after late latent disease.