Lunate bone loss associated with Chlamydia pneumoniae infection.

Respiratory pathogens such as Chlamydia pneumoniae may activate osteoclast cells, thereby inducing bone resorption and joint inflammation. Herein is a case report of a young man with misdiagnosed persistent wrist pain without any major trauma. Investigation of the patient's medical history confirmed a recent systemic C. pneumoniae infection. Preoperative X-ray and magnetic resonance imaging (MRI) showed a substantial decrease in cancellous lunate bone compactness. A stepwise approach was undertaken considering the rapid onset of bone devascularisation and the clinical presentation. Wrist arthroscopy confirmed extensive joint inflammation associated with decreased osteochondral lunate solidity. Microbiological examination excluded joint infection. Histological analysis showed a diffuse inflammatory infiltration. Temporary mediocarpal K-wire stabilization and synovectomy were performed. Postoperative MRI confirmed lunate bone revascularization. At 6 and 12 months' follow-up the young man was pain-free and had good recovery of range of motion. In vitro and in vivo studies demonstrate that inflammatory conditions may promote osteoclast cell activity and induce bone resorption. Moreover, infection with C. pneumoniae could activate specific "osteoporotic" bone pathways. To the authors' knowledge, this is the first published case report of specific lunate bone loss induced by systemic C. pneumoniae infection. The authors proposed an etiologic explanation, and a stepwise approach was associated with good outcome.