Review Question - QID 215011

A 34-year-old G1P1 woman presents to the clinic with her 8-month-old boy for a well-child visit. She has no significant past medical history. She did not receive prenatal care during the pregnancy. The child was born at 39 weeks of gestation via an uncomplicated spontaneous vaginal delivery. She reports a prior history of multiple sexual partners and occasional intravenous drug use. She reports that her baby is doing well, but is developing a little differently from other children of the same age at daycare. The infant's temperature is 36.8°C (98.2°F), blood pressure is 96/50 mmHg, pulse is 120/min, respirations are 30/min, and oxygen saturation is 100% on room air. Physical exam reveals the findings shown in Figure A and B. Bilateral anterior bowing of the tibia is also noted. Which of the following is the most likely diagnosis?