Bone Abstracts

Objectives: To characterize clinical features and long-term outcome of CRMO, a rare inflammatory bone disease of childhood and adolescence, which forms part of the spectrum of chronic non-bacterial osteomyelitis (CNO).

Methods: We studied 33 patients with an established diagnosis of CRMO followed at the Centre for Bone Quality of the Leiden University Medical Center from 1994 to 2018. Demographic and clinical data were collected at presentation and last follow-up control.

Results: There were 22 girls and 11 boys with a median age of 11 years (range 5–17) at first symptom(s). Delay in diagnosis was 1.5±2 years. Presentation was with acute bone pain in all, predominantly in one or more long bone. Local inflammatory manifestations (soft tissue and bone) were present in 14 patients and decreased function in 8. Five patients had palmoplantar pustulosis, and 11 an autoimmune disease, 6 psoriasis. Lesions of lower limbs were most common (n=18), mainly of tibia (n=12). Thirteen had sternocostoclavicular lesions, and one a mandibular lesion. The majority (73%) had multiple bone lesions (2–15). Over 50% had increased ESR and/or CRP. When measured (n=23) P1NP and CTx were increased in a minority (1 and 6 respectively). 58% of patients had a bone biopsy to exclude bacterial osteomyelitis, malignancies or other bone pathology. All received NSAIDs, 22 iv bisphosphonates, 5 methotrexate and 5 anti-TNFα. At time of study median duration of follow up was 6 years (range 1–25), and median age was 17 years (range 11–41). One patient was lost to follow up, 21 were completely asymptomatic, 16 of whom off treatment. Eleven patients had still mild to moderate recurrent symptoms requiring treatment.

Conclusion: CRMO is a rare inflammatory bone disorder associated with variable local and systemic manifestations. The disease presents acutely and responds to treatment with NSAIDs, and/or iv bisphosphonates or anti-TNFα. In our cohort, long-term clinical outcome of CRMO was good, with over 2/3 of patients being asymptomatic by a median age of 16 years, the majority of whom off treatment. A minority of patients had persistent intermittent mild recurrent symptoms requiring treatment. Further studies are required to identify patients at risk from persistent disease.

Disclosure: The authors declared no competing interests.