Musculoskeletal Imaging

Syphilis

a chronic systemic infectious disease caused by the spirochaete Treponema pallidum, usually spread during sexual contact. In some cases, however, an acquired syphilis may result in children from sharing a bed with an infected person, and congenital syphilis may occur in a fetus after transmission of the organism through the placenta. About 36 weeks after the organism has entered the body, in the primary stage of the disease, the initial skin ulceration, or chancre, develops at the site of inoculation. Approximately 6 weeks later, secondary syphilis is heralded by a generalized skin eruption. Both primary and secondary manifestations subsequently disappear, and the patient may be asymptomatic for a protracted period of time (latent syphilis), even although progressive inflammatory alterations may be occurring in many organ systems. Large destructive lesions or gummas can be evident in any organ, particularly the skin and the bones.

In congenital syphilis, the hutchinsonian triad of Hutchinsons teeth, interstitial keratitis and nerve deafness may be evident. Other findings include rhagades about the mouth and anus, sabre shin deformity and saddle nose deformity. Bone lesions include syphilitic osteochondritis at sites of endochondral ossification. On radiographs broad horizontal radiolucent bands similar to those observed in leukaemia or metastasis from neuroblastoma are noted. With progression, irregularities of the metaphyses appear. Erosions may develop, especially on the medial surface of the proximal tibial shaft (Wimbergers sign). Diaphyseal osteomyelitis (osteitis) results from extension of granulation tissue; surrounding bony eburnation and overlying periostitis are also seen. Periostitis develops from infiltration by syphilitic granulation tissue. Alternatively, reparative (reactive) periostitis may be noted about healing foci of osteochondritis or after epiphyseal slipping.

In acquired syphilis, bone and joint abnormalities do not always occur but when present usually appear in the latent or tertiary phase. In the early phases, osteochondritis, periostitis, osteitis or osteomyelitis may be evident. Bone lesions occurring during the later stages of acquired syphilis can be due to gummatous or nongummatous inflammation. Both gummatous and nongummatous bone involvement produces an identical radiographic picture, with lysis and sclerosis of bone, which may reach considerable size. The radiographic and pathologic features resemble those in the late stages of congenital syphilis, including the sabre shin deformity.

Joint abnormalities may occur in either congenital or acquired forms of the disease. Joint effusions associated with pain and tenderness, which may be infectious or noninfectious, are commonly bilateral and most typically affect the knee.

Neurosyphilis can lead to a neuropathic osteoarthropathy; in this condition, fragmentation and dissolution of one or more joints of the axial and appendicular skeleton may occur (Fig.1). Tabes dorsalis, a disorder characterized by progressive atrophy of the posterior columns and posterior roots or ganglia of the spinal cord, may affect the knee, hip, ankle, glenohumeral joint, elbow and spine.

An infectious arthritis may also occur in syphilis, associated with an effusion and capsular distension. Synovial inflammation with pannus can lead to cartilage and bone destruction. On radiographs, osteoporosis, joint space narrowing, bone destruction, sclerosis and intra-articular osseous fusion can be encountered.

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Fig.1

AP radiographs of the right (a) and left (b) knee demonstrates osteoarticular destruction and bone fragmentation owing to tabes dorsalis. (Courtesy of Elke Pirieda, MD, Catoduva, Brazil)
Syphilis, Fig.1 (a)
Syphilis, Fig.1 (b)