Uptick in adult syphilis means congenital syphilis may be lurking

While many pediatric clinicians have not frequently managed newborns of mothers with reactive syphilis serology, increased adult syphilis may change that.¹

Dr. Christopher J. Harrison

Diagnosing/managing congenital syphilis is not always clear cut. A positive rapid plasma reagin (RPR) titer in a newborn may not indicate congenital infection but merely may reflect transplacental, passively acquired maternal IgG from the mother’s current or previous infection rather than antibodies produced by the newborn. Because currently no IgM assay for syphilis is recommended by the Centers for Disease Control and Prevention for newborn testing, we must deal with IgG test results.

Often initial management decisions are needed while the infant’s status is evolving. The questions to answer to make final decisions include the following²:

• Was the mother actively infected with Treponema pallidum during pregnancy?
• If so, was the mother appropriately treated and when?
• Does the infant have any clinical, laboratory, or radiographic evidence of syphilis?
• How do the mother’s and infant’s nontreponemal serologic titers (NTT) compare at delivery using the same test?

Note: All infants assessed for congenital syphilis need a full evaluation for HIV.

Managing the infant of a mother with positive tests^3,4

All such neonates need an examination for evidence of congenital syphilis. The clinical signs of congenital syphilis in neonates include nonimmune hydrops, jaundice, hepatosplenomegaly, rhinitis, skin rash, and pseudoparalysis of extremity. Also, consider dark-field examination or polymerase chain reaction (PCR) of lesions (such as bullae) or secretions (nasal). If available, have the placenta examined histologically (silver stain) or by PCR (Clinical Laboratory Improvement Amendments–validated test). Skeletal radiographic surveys are more useful for stillborn than live born infants. (The complete algorithm can be found in Figure 3.10 of reference 4.)

Order a quantitative NTT, using the Venereal Disease Research Laboratory (VDRL) test or RPR test on neonatal serum. Umbilical cord blood is not appropriate because of potential maternal blood contamination, which could give a false-positive result, or Wharton’s jelly, which could give a false-negative result. Use of treponemal-specific tests that are used for maternal diagnosis – such as T. pallidum particle agglutination (TP-PA), T. pallidum enzyme-linked immunosorbent assay (TP-EIA), fluorescent treponemal antibody absorption (FTA-ABS) test, or T. pallidum chemiluminescence immunoassay (TP-CIA) – on neonatal serum is not recommended because of difficulties in interpretation.

Diagnostic results allow designation of an infant into one of four CDC categories: proven/highly probable syphilis; possible syphilis; syphilis less likely; and syphilis unlikely. Treatment recommendations are based on these categories.

Proven or highly probable syphilis

There are two alternative recommended 10-day treatment regimens.

A. Aqueous crystalline penicillin G 100,000-150,000 U/kg per day by IV at 50,000 U/kg per dose, given every 12 hours through 7 days of age or every 8 hours if greater than 7 days old.

B. Procaine penicillin G at 50,000 U/kg per dose intramuscularly in one dose each day.