With syphilitic infection, the placenta becomes large and pale (see Fig. 65-4). Microscopically, villi lose their characteristic arborization and become thicker and clubbed. Sheield and colleagues (2002c) described these villi in more than 60 percent of syphilitic placentas. Blood vessels markedly diminish in number, and in advanced cases, they almost entirely disappear as a result of endarteritis and stromal cell proliferation. Likely related, Lucas and coworkers (1991) demonstrated increased vascular resistance in uterine and umbilical arteries of infected pregnancies. he cord may also show evidence of infection. In a study of 25 untreated women, Schwartz and associates (1995) reported that necrotizing funisitis was present in a third.
The United States Preventative Services Task Force recom mends that clinicians screen all pregnant women for syphilis to prevent congenital infection (Wolf, 2009). Testing is ideally performed at the irst prenatal visit. In populations with a high prevalence of syphilis, serological testing is repeated in the third trimester and again at delivery (Workowski, 2015).
Treponema pallidum cannot be cultured from clinical specimens. However, direct diagnosis of early-stage disease from lesion exudate, tissue, or body luid can be completed by darkield microscopic examination, by polymerase chain reaction (PCR), or by direct fluorescent antibody tests for T pallidum (DFA-TP) (Tsang, 2015). hese methods are not widely available and are less sensitive for blood specimens (Grange, 2012; HenaoMartinez, 2014). hus, in practice, diagnoses are mainly derived from clinical indings coupled with serological blood testing.
Serological testing is used for diagnostic and for screening purposes. here are two types. If the irst of these is positive, then the second type is also performed. his combination identifies infection and clariies disease stage. Traditionally, the first type is nontreponemal testing, and either the Venereal Disease Research Laboratory (VDRL) or the rapid plasma reagin (RPR) is selected. Both tests measure patient immunoglobulin M and G (IgM and IgG) antibodies formed against cardiolipin that is released from damaged host cells and possibly also from treponemes. Notably, these same antibodies can also be produced in response to other acute events that include recent vaccination, febrile illness, and pregnancy itself or in response to chronic conditions such as intravenous drug abuse, systemic lupus erythematosus, aging, leprosy, or cancer. As such, these all serve as potential sources of false-positive results (Larsen, 1995). Conversely, seroconversion occurs at around 3 weeks, but can take up to 6 weeks (Peeling, 2004). Thus, women with very early primary syphilis can have initially false-negative serological test results.
FIGURE 65-4 Congenital syphilis. A. Fetogram of a stillborn infant infected with syphilis showing the "moth-eaten" appearance of the femurs (arrow). B. Enlarged hydropic placenta of a syphilis-infected neonate.