Chapter 147: Syphilis

I. DEFINITION

Syphilis is a sexually transmitted infection caused by Treponema pallidum, which is a thin, motile spirochete that is extremely fastidious, surviving only briefly outside the host. The Centers for Disease Control and Prevention (CDC) issued a case definition of congenital syphilis (CS) in 2018 as follows: a condition caused by infection in utero with T pallidum. A wide spectrum of severity exists, from inapparent infection to severe cases that are clinically apparent at birth. Laboratory criteria for diagnosis entail demonstration of T pallidum by: (1) darkfield microscopy of lesions, body fluids, or neonatal nasal discharge; or (2) polymerase chain reaction (PCR) or other equivalent direct molecular methods of lesions, neonatal nasal discharge, placenta, umbilical cord, or autopsy material; or (3) immunohistochemistry or special stains (eg, silver staining) of specimens from lesions, placenta, umbilical cord, or autopsy material. Cases are classified as confirmed (by laboratory diagnosis) or probable. Probable CS is a condition affecting an infant whose mother had untreated or inadequately treated syphilis at delivery, regardless of signs in the infant, or an infant or child who has a reactive nontreponemal test for syphilis (Venereal Disease Research Laboratory [VDRL], rapid plasma reagin [RPR], or equivalent serologic methods) and any 1 of the following: (1) any evidence of CS on physical examination; (2) any evidence of CS on radiographs of long bones; (3) a reactive cerebrospinal fluid (CSF) VDRL test; (4) an elevated CSF leukocyte (white blood cell [WBC]) count or protein (without other cause) in a nontraumatic lumbar puncture. Suggested parameters for abnormal CSF WBC and protein values include the following: during the first 30 days of life, a CSF WBC count of >15 WBC/mm³ or a CSF protein >120 mg/dL is abnormal; after the first 30 days of life, a CSF WBC count of >5 WBC/mm³ or a CSF protein >40 mg/dL is abnormal, regardless of CSF serology. Adequate treatment is defined as completion of a penicillin-based regimen, in accordance with CDC treatment guidelines, appropriate for stage of infection, initiated ≥30 days before delivery.

II. INCIDENCE

According the CDC, from 2013 through 2017, there was a 76% increase in cases of syphilis in the United States (from 17,375 to 30,644 cases). The incidence of CS parallels that of primary and secondary syphilis in the general population. In the United States, in 2016, there were a total of 628 reported cases of CS, including 41 syphilitic stillbirths, with a national rate of 15.7 cases per 100,000 live births. This rate represents an increase of 86.9% relative to 2012. Worldwide, syphilis continues to represent a serious public health problem; a World Health Organization analysis showed that in 2012, an estimated 930,000 maternal syphilis infections caused 350,000 adverse pregnancy outcomes including 143,000 early fetal deaths and stillbirths, 62,000 neonatal deaths, 44,000 preterm or low-weight births, and 102,000 infected infants worldwide. The rate of CS is increased among infants born to mothers with ...