Conclusion
In the case presented T. pallidum was identified as the unexpected cause of a vertebral osteitis. Clinically significant osteitis and osteomyelitis are rare complications of secondary syphilis unlike bone involvement in congenital and tertiary syphilis.
The syphilitic bone lesions usually have origin in the periostitis but can spread to the subjacent bone. The most frequently affected bones are tibia and the skull.
In our case, an HIV positive male with early stage of syphilis, as he had a negative syphilis serology 7 months prior to admission had osteitis. There was no recognized chancre unless the throat pain represented an undiagnosed chancre. The nocturnal shin pain our patient described is a typical symptom of syphilitic periostitis and often accompanied by swelling and erythema. Thus, the findings on the scintigraphy with tibial and cranial activity are compatible with periostitis.
As the osseous lesions can be hard to encounter the prevalence of bone involvement in syphilis is unknown. In one study two patients out of 851 (0.2%) had periostitis. In another x-ray study survey of the skulls of 80 patients with secondary syphilis, 7 patients (9%) had cranial lesions. The by far largest study performed by Reynolds and Wasserman in 1942 found that only 15 patients out of 10.000 (0.15%) with syphilis had destructive bony changes.
During the last decades a number of cases of bone involvement in early syphilis have been reported. In these cases the diagnosis has primarily been reached by radiological findings (bone scintigraphy, MRI, x-ray). Only one case of syphilitic osteitis where the diagnosis is obtained by PCR technique has been formerly reported. In very few cases spirochetes have been isolated from bone biopsy. Recently, increasing incidence of syphilis, especially among MSM, has been reported across Europe. In Denmark, the number of reported cases has tripled from 2008 to 2009 and the increase continues within 2010. In California there was a >700% increase in primary and secondary syphilis cases reported between 1999 and 2005, and 80% of these cases involved MSM. Furthermore 60% of MSM with syphilis were co-infected with HIV. The increasing incidence of STD may indicate a decrease in the safe sex practice that may be due to the decreased awareness of HIV transmission after well established antiretroviral treatment. With this in mind syphilitic osteitis should be considered for at-risk patients with bone symptoms or with lytic bone lesions.
In conclusion we describe an atypical presentation of syphilis in a young HIV infected male with osteitis in vertebrae including the dens of axis caused by T pallidum. MRI changes lead to bone biopsy and subsequently the diagnosis of syphilis obtained by specific PCR technique. The rare location of a syphilitic osteitis and the diagnostic approach make this case unique.