Rastreio pré-natal da sífilis – serão os resultados sempre fiáveis?

Introduction: Congenital syphilis (CS) can be acquired by the fetus during pregnancy or delivery. When asymptomatic at birth, newborns usually present the first clinical signs by the age of three months.Case report: We report the case of a three-month old infant presenting with severe anemia, hepatosplenomegaly, and vesicular rash with shedding palmoplantar erythema. The pregnancy was unremarkable. The blood work revealed severe non-immune hemolytic anemia, thrombocytopenia, and hepatitis. The initial rapid plasma reagin (RPR) screening for syphilis was negative. However, due to a high index of suspicion, a second RPR test was performed, with a positive result, which may be explained by the prozone phenomenon. Conclusion: This case shows that a negative prenatal syphilis test does not rule out a diagnosis of CS. In the presence of compatible clinical findings and a high index of suspicion, extensive evaluation should be considered. We highlight the importance of serum dilution to overcome the prozone phenomenon.