Secondary syphilis at 32 weeks with a high RPR titre — structured SAQ (15 marks)

(a) Staging and vertical transmission risk (2 marks)

One mark for the stage, one for the transmission risk in that stage. ^[1]

• Stage: secondary syphilis — the rash (especially involving the palms and soles) and the condylomata lata are pathognomonic of the secondary stage, which follows haematogenous dissemination of the spirochaete after the primary chancre.^[1]
• Vertical transmission risk: untreated secondary syphilis carries the highest vertical transmission rate of any stage. Transmission can occur at any gestation, and the risk of congenital syphilis, stillbirth, neonatal death and prematurity is highest in primary and secondary disease.^[1]

(b) Treatment regimen and the penicillin rationale (4 marks)

One mark each for the agent, the dose and route, the number of doses, and the penicillin-only rationale. ^[1][3]

• Agent: benzathine penicillin G.^[1]
• Dose and route: 2.4 million units intramuscularly.^[1]
• Number of doses: a single dose for secondary (and primary, and early latent) syphilis. Three weekly doses are reserved for late latent, unknown-duration and tertiary syphilis. The Kaminiów 2026 randomised trial confirmed no added benefit from intensifying early syphilis with three weekly doses.^[1][3]
• Penicillin-only rationale: benzathine penicillin G is the only recommended treatment for syphilis in pregnancy. Doxycycline and tetracycline are contraindicated, and azithromycin is precluded by resistance. A penicillin-allergic pregnant woman is desensitised and treated with penicillin — there is no alternative antibiotic in pregnancy.^[1]

(c) Jarisch-Herxheimer counselling and fetal monitoring (4 marks)

One mark each for the timeline, the symptoms to counsel on, the fetal monitoring plan, and the principle of not delaying treatment. ^[2]

• Timeline: onset 2 to 8 hours after treatment, peak at 6 to 12 hours, resolution by 16 to 24 hours. The frequency in pregnancy is about 45% overall and 60% in secondary syphilis.^[2]
• Counselling: advise the woman to seek obstetric attention if she develops fever, uterine contractions or reduced fetal movements after treatment.^[1][2]
• Fetal monitoring: maternal observations and a CTG through the 2 to 24 hour window, given that uterine contractions and reduced fetal movements occur in roughly two-thirds of reactors and transient late decelerations can occur.^[2]
• Principle: the reaction is monitored, not avoided by delaying treatment — the risk to the fetus of untreated secondary syphilis vastly exceeds the reaction risk. Corticosteroid prophylaxis is not supported by evidence in pregnancy.^[1][2]

(d) Serological follow-up and the rising titre (5 marks)

One mark each for the test used to monitor, the definition of adequate response, the timing, the rising-titre interpretation, and the management of treatment failure or reinfection. ^[1]

• Test: the non-treponemal titre (RPR or VDRL), quantitative. Treponemal tests do not monitor response — they stay reactive for life.^[1]
• Adequate response: at least a fourfold (two-dilution) decline in non-treponemal titre — for example 1:128 to 1:32 — over the expected window.^[1]
• Timing: assessment at 6 to 12 months for early syphilis, with a longer window for late latent syphilis.^[1]
• Rising titre after an adequate decline: this signals reinfection or treatment failure. Re-stage clinically, re-test for HIV, re-test the partner.^[1]
• Re-treatment: re-treat with three weekly doses of benzathine penicillin G (regardless of stage, for a documented failure or reinfection), and consider cerebrospinal fluid examination if neurosyphilis is suspected.^[1]