Introduction

Congenital syphilis affects multiple organ systems, with the skeletal system being involved in 60–80% of infants with clinical signs. Diagnosis relies on a combination of clinical features, radiographic findings, and laboratory confirmation, as no single test is 100% sensitive in the newborn period.

1. Radiological Features

Radiographic abnormalities of the long bones are often the most helpful diagnostic sign because they are frequent and appear early. They may be the only abnormality in an otherwise asymptomatic infant born to a mother with untreated syphilis.

A. Metaphysitis (Osteochondritis)

This is the most characteristic lesion, primarily affecting the femur and humerus.

• Wegner’s Sign: A serrated or "saw-tooth" appearance at the epiphyseal margin. This represents points of calcified cartilage along the nutrient cartilage canals.
• Wimberger’s Sign: Localized demineralization or erosion of the medial aspect of the proximal tibial metaphysis. This is a classic and highly specific sign of congenital syphilis,.
• Irregularity of Provisional Calcification: Bands of metaphyseal lucency may occur at the epiphyseal plate.

B. Periostitis

• This manifests as thickening of the bone cortices due to new bone formation.
• It typically involves the long bones and, rarely, the skull.
• It may present as single or multiple layers of new bone, sometimes giving a "bone-within-a-bone" appearance.

C. Other Radiological Findings

• Pneumonia Alba: Chest X-ray may show complete opacification of lung fields or a diffuse, fluffy infiltrate. This represents obliterative fibrosis and scarring of alveolar walls.
• Late Manifestations (>2 years):
  • Saber Shins: Anterior bowing of the midportion of the tibia due to chronic periostitis,.
  • Clutton Joints: Symmetrical hydrarthrosis (effusion) of the knees, usually painless.
  • Higouménakis Sign: Unilateral or bilateral thickening of the sternoclavicular third of the clavicle.

2. Confirmatory Laboratory Tests

A definitive diagnosis is established when Treponema pallidum is identified in clinical specimens or when specific serologic criteria are met.

A. Direct Visualization (The Gold Standard)

• Darkfield Microscopy: The visualization of spirochetes in specimens from moist lesions (e.g., bullae, snuffles discharge, mucous patches), placenta, or umbilical cord confirms the diagnosis,.
• Direct Fluorescent Antibody (DFA): Staining of exudates or tissues with specific antitreponemal antibodies can identify the organism if darkfield microscopy is unavailable.

B. Serological Confirmation

• Quantitative Nontreponemal Tests (RPR/VDRL):
  • A serum quantitative nontreponemal titer in the infant that is fourfold (4x) or greater than the mother’s titer (e.g., Mother 1:4, Infant 1:16) is diagnostic of congenital syphilis,.
  • Note: Tests should be performed on infant serum, not cord blood, to avoid contamination with maternal blood.
• Treponemal Tests (TPHA/TP-PA/FTA-ABS):
  • A reactive treponemal test after the infant is 18 months of age confirms the diagnosis. By this age, passively transferred maternal antibodies have disappeared,.
  • IgM Assays: Specific IgM tests (e.g., IgM-FTA-ABS or IgM immunoblotting) can detect endogenous fetal antibody production. However, due to variable sensitivity (false negatives) and specificity, they are often used as supportive rather than definitive singular diagnostic tools in some settings,.

C. Molecular Methods

• Polymerase Chain Reaction (PCR): PCR assays on neonatal blood, CSF, or lesions are highly specific and are increasingly used to detect T. pallidum DNA, confirming the diagnosis even when serology is equivocal,.

D. CSF Analysis (Neurosyphilis)

• CSF VDRL: A reactive VDRL in the cerebrospinal fluid is considered specific for neurosyphilis, although it may have low sensitivity,.

Management of a Neonate Born to a VDRL Positive Mother

Introduction

The management of a neonate born to a mother with reactive serology (VDRL/RPR positive) depends on three factors:

1. Documentation of maternal infection and treatment history.
2. Clinical examination of the neonate.
3. Comparison of maternal and neonatal nontreponemal titers.

All infants born to seropositive mothers should be evaluated for HIV, as coinfection is common.

Step 1: Maternal Risk Assessment

The mother is considered Inadequately Treated if she:

• Received No treatment or undocumented treatment.
• Was treated < 4 weeks before delivery.
• Was treated with a non-penicillin regimen (e.g., erythromycin).
• Shows evidence of relapse or reinfection (4-fold rise in titer),.

Step 2: Evaluation and Treatment Scenarios

Based on the risk stratification, infants are categorized into four scenarios,,.

Scenario 1: Proven or Highly Probable Disease

Criteria:

• Abnormal physical exam consistent with congenital syphilis (snuffles, hepatosplenomegaly, rash, etc.).
• Serum quantitative nontreponemal titer $\ge$ 4-fold higher than mother's titer.
• Positive darkfield microscopy/PCR from body fluids/lesions.

Action:

1. Full Workup: CSF analysis (VDRL, cell count, protein), CBC with platelets, Long bone X-rays.
2. Treatment:
   • Aqueous Crystalline Penicillin G: 50,000 units/kg/dose IV every 12 hours (first 7 days) then every 8 hours, for a total of 10 days.
   • OR Procaine Penicillin G: 50,000 units/kg/dose IM daily for 10 days.

Scenario 2: Possible Congenital Syphilis

Criteria:

• Normal physical exam.
• Infant titer < 4-fold of maternal titer.
• Mother was Inadequately Treated (as defined above).

Action:

• Option A (Preferred): Perform full workup (CSF, CBC, X-rays).
  • If workup is abnormal: Treat as Scenario 1 (10 days IV Penicillin).
  • If workup is normal: Single dose Benzathine Penicillin G (50,000 units/kg IM).
• Option B (No full workup): If full evaluation is not possible or follow-up is uncertain, treat blindly with IV/IM Penicillin for 10 days (covers potential neurosyphilis).

Scenario 3: Congenital Syphilis Less Likely

Criteria:

• Normal physical exam.
• Infant titer < 4-fold of maternal titer.
• Mother was Adequately Treated during pregnancy (>4 weeks before delivery) with no evidence of reinfection.

Action:

• No full evaluation required.
• Treatment: Single dose Benzathine Penicillin G (50,000 units/kg IM).
• rationale: Maternal treatment failure occurs in a small percentage of cases, and ensuring follow-up can be difficult.

Scenario 4: Congenital Syphilis Unlikely

Criteria:

• Normal physical exam.
• Infant titer < 4-fold of maternal titer.
• Mother treated BEFORE pregnancy and titers have remained low/stable (serofast) during pregnancy and delivery.

Action:

• No treatment required.
• Some experts recommend Benzathine Penicillin G (single dose) if follow-up is uncertain.

Step 3: Follow-up Monitoring

Proper follow-up is essential to ensure cure and exclude developmental sequelae,.

1. Serology (RPR/VDRL):
   • Repeat at 2, 4, 6, and 12 months.
   • Titers should decline by 3 months and become non-reactive by 6 months.
   • If titers persist >6–12 months or rise, re-evaluate (including CSF) and treat.
2. Treponemal Tests:
   • Perform at 12–18 months. A positive test at 18 months confirms congenital syphilis.
3. Neurosyphilis:
   • If initial CSF was abnormal, repeat LP every 6 months until normal.
4. General:
   • Monitor for vision, hearing, and neurodevelopmental status.

Summary of Treatment Doses

• Aqueous Penicillin G: 50,000 U/kg/dose IV (q12h <7 days; q8h >7 days) for 10 days.
• Procaine Penicillin G: 50,000 U/kg/dose IM daily for 10 days.
• Benzathine Penicillin G: 50,000 U/kg IM single dose.