Teaching Case

A 4-day-old late pre-term infant was born to a woman found to have a positive reactive plasma reagin (RPR) test. The infant also showed a positive RPR and thrombocytopenia. There was no prenatal care or prior ultrasound.

AP radiograph of both upper and lower extremities showed symmetrical metaphyseal lucent bands (Fig. 1, 2). There is also an irregularity of the metaphysis involving the long bones of the upper and lower extremities with sparing of the thin radiodense periphyseal zones of provisional calcification. No significant periosteal reaction was seen.

Congenital syphilis results from the transmission of the spirochete Treponema pallidum (T. pallidum) from infected mother to fetus through the placenta. It can occur as early as 9 weeks gestation through to the end of pregnancy and results in spread of T. pallidum mostly to the bones, brain, liver, and lungs [1]. Although congenital syphilis is still considered uncommon, the rate increase of 38% from 2012 to 2014 makes this an ongoing public health concern [2].

The typical clinical presentation for a live infant is dependent on when the infection was acquired [1]. Common clinical findings include rash, fever, hepatosplenomegaly, leukocytosis, anaemia, and thrombocytopaenia [1, 2]. Skeletal changes on radiographic evaluation are evident in up to 80% of patients diagnosed early [1]. Given the morbidity of syphilis if undetected and untreated, along with the lack of examination findings specific to the disease, the Center for Disease Control (CDC) recommends long-bone radiographs in the diagnostic evaluation of congenital syphilis [3, 4].

The most common radiographic findings include bilateral and symmetrical bands of lucency involving the metaphysis of long bones with periosteal reaction thought to be secondary to alterations in bone growth [3, 5]. Additional findings include separation of the epiphysis, pathologic fractures, or alterations in normal joint anatomy [3]. Although bony findings do not always correlate with the physical examination, disruptions in bone architecture can cause pain and decreased range of motion resulting in “Parrot pseudoparalysis”, a term used to describe reduced extremity motion resulting from periostitis [3]. The clinical history, laboratory, and radiographic findings for this patient were consistent with a diagnosis of congenital syphilis.