Clinical spectrum of congenital syphilis ranges from asymptomatic infection to fulminant sepsis. Treponema pallidum is acquired crossing the placenta from the mother to the fetus during maternal spirochetemia or through direct contact of the child with an infected lesion at delivery. We report a 27 days-old previously healthy girl diagnosed with congenital syphilis. Her mother had an unremarkable previous history, adequate obstetric care and negative prenatal screening test for syphilis. The patient was brought to the ER due to development of skin lesions and fever in the last 24 h. She was admitted to pediatric ICU lethargic and poorly responsive, with hepa-tosplenomegaly and perioral, palmoplantar erythematous desquamative scaly lesions. Laboratory data revealed anemia, leukocytosis, thrombocytopenia and C-reactive protein of 183 mg/l. Soon after admission she developed septic shock with leukocytosis up to 45,800/mm3 and exacerbation of thrombocytopenia, hypoalbuminemia and metabolic acidosis. Congenital syphilis was diagnosed at the second day of admission with VDRL titers of 1:128 in serum and 1:8 in cerebrospinal fluid. Maternal serum VDRL was positive with titers of 1:32. The patient was treated with penicillin for three weeks with adequate clinical and laboratory response. Congenital syphilis is a life threatening infection, but cannot always be diagnosed at birth. Health care workers must be aware of the difficulties in obtaining a definitive diagnosis and must have a high index of suspicion, considering the possible errors of prenatal serology and the diverse possible clinical presentations, including neonatal sepsis during the first month of life.