Objectives: Chronic non-bacterial osteomyelitis (CNO) is an autoinflammatory disorder of the skeletal system. Treatment with NSAIDs is generally effective in the majority of patients, however, a sizeable proportion of patients have persistent disease and subsequent treatment strategies are required. The aim of this study was to characterise the clinical and radiological disease course in CNO patients treated with the bisphosphonate pamidronate (PAM).
Methods: Eight CNO patients refractory to NSAIDs, glucocorticoids and sulfasalazine were treated with 6 cycles of PAM in four-weekly intervals. The disease course was assessed by clinical examination and whole-body (WB) MRI at standardised time points during the treatment phase and in a 6 months follow-up.
Results: Seven patients were in complete clinical remission after 6 applications of PAM. WB MRIs showed regression of inflammatory lesions in 7 patients with complete remission in only one patient and partial remission in 6 patients. One patient developed radiological progression despite a marked improvement of clinical symptoms. In the follow-up after PAM therapy, 3 patients developed MRI confirmed relapse. Additional applications of PAM induced a sustained clinical remission and partial radiological response in two of them. Mild temporary adverse effects were noted in 5 patients.
Conclusions: Our study highlights that PAM is effective in controlling clinical symptoms (e.g. pain) in CNO patients. However, subclinical bone inflammation was still detectable by MRI in most of the patients and disease progression was noticed in some patients after cessation of PAM.