Congenital syphilis and perinatal sexually transmitted infections — formative SAQs

SAQ 1 (10 marks)

A two-week-old infant from a remote northern Australian community is brought in with poor feeding, fever, and a swollen abdomen. On examination there is hepatosplenomegaly, a copper-coloured maculopapular rash on the palms and soles, generalised lymphadenopathy, and a profuse blood-tinged nasal discharge. The left arm is held still and appears tender. The mother booked late to antenatal care; her syphilis serology was treated with a single dose of benzathine penicillin only ten days before an uncomplicated vaginal delivery. ^[3]

Question: Outline the diagnosis, investigations, immediate and stepwise management of this infant, including the maternal-treatment-adequacy review and public-health follow-up. (10 marks) ^[6]

Model answer

Diagnosis and disposition (2 marks). This is classic early congenital syphilis: hepatosplenomegaly, the copper maculopapular rash on palms and soles, generalised lymphadenopathy, snuffles (the profuse blood-tinged nasal discharge teeming with spirochaetes), and the painful osteochondritis causing pseudoparalysis of Parrot in the left arm. The maternal treatment gap (only ten days before delivery, far less than the four weeks needed for prevention) confirms high risk. Admit for full evaluation, empiric therapy, and isolation for the infectious secretions. ^[6]

Investigations (3 marks). Send comparative serology: a quantitative non-treponemal test (RPR) on the infant compared with the maternal titre — a neonatal titre fourfold or more higher than maternal strongly suggests true congenital infection — plus treponemal IgM (19S-IgM), which does not cross the placenta and confirms active neonatal infection. Add a full blood count and film (anaemia, thrombocytopenia), liver function tests, a lumbar puncture for CSF cell count, protein and CSF VDRL, and long-bone radiographs for the osteochondritis and periostitis. Dark-field microscopy or PCR of the nasal discharge can demonstrate spirochaetes directly. Confirm the maternal serology and treatment record. ^{[6] [3]}

Treatment (3 marks). Treat with aqueous crystalline penicillin G intravenously for ten days, because the CNS must be penetrated and benzathine penicillin does not achieve reliable CSF concentrations. Provide supportive care — fluids, transfusion for severe anaemia, antipyretics — and treat intercurrent problems. Isolate for the infectious secretions with standard precautions and gloves. Do not use a single benzathine dose for a symptomatic infant. ^[6]

Maternal-treatment review and public health (2 marks). Review the maternal treatment adequacy: a single benzathine dose ten days before delivery is inadequate by timing — the four-week-before-delivery rule was not met — placing the infant at high risk. Notify public health, trigger partner notification and treatment, and arrange maternal and partner sexual-health follow-up. Plan long-term infant surveillance: quantitative non-treponemal serology every two to three months until non-reactive, plus developmental, audiological and ophthalmological surveillance for the late stigmata (Hutchinson teeth, interstitial keratitis, eighth-nerve deafness). Address the access barriers (remoteness, late booking) that drove the missed prevention. ^{[11] [14]}