OBJECTIVE: Extra-osseous (EO) manifestations are poorly characterized in chronic recurrent multifocal osteomyelitis (CRMO). This study aimed to further define the frequency, characteristics and treatment of EO events in CRMO and whether different phenotypes can be distinguished and benefit from special management.
METHODS: This multicentre retrospective study included CRMO patients followed in several paediatric rheumatology departments in France between 2015 and 2022. EO manifestations were defined as skin lesions, gastrointestinal manifestations, arthritis, enthesitis, sacroiliitis, uveitis, vasculitis and fever. At the last visit, the physician defined CRMO as active in the presence of clinical manifestations including both osseous and EO symptoms.
RESULTS: We included 133 patients; 87 (65.4%) were girls and the median age at first symptoms was 9.0 years (interquartile range 7.0-10.0). EO manifestations were described in 90 (67.7%) patients, with a predominance of skin lesions [n = 51/90 (56.7%)], followed by sacroiliitis [n = 38/90 (42.2%)], enthesitis [n = 21/90 (23.3%)], arthritis [n = 14/90 (15.6%)] and gastrointestinal manifestations [n = 6/90 (6.7%)]. The use of non-steroidal anti-inflammatory drugs and bisphosphonates did not differ by the presence or not of EO manifestations. Biologics were taken more frequently by patients with than without EO manifestations (P < 0.001); TNF inhibitors were used in 33 (36.7%) EO-positive patients. Under this treatment, 18 (54.5%) patients achieved complete remission of osseous and EO manifestations. At the last visit, more EO+ than EO- patients were on treatment (P = 0.009), with active disease in 58 (64.4%) patients.
CONCLUSIONS: The analysis of EO manifestations in CRMO delineates two groups of patients in terms of severity and treatments used. Our study opens up new pathophysiological leads that may underlie the wide range of CRMO phenotypes.

UNASSIGNED: Osteomyelitis is a group of bone infectious (bacterial osteomyeilitis-BO) and noninfectious inflammatory diseases (nonbacterial osteomyelitis-NBO) with similar clinical, radiology, and laboratory features. Many patients with NBO are misdiagnosed as BO and receive unnecessary antibiotics and surgery. Our study aimed to compare clinical and laboratory features of NBO and BO in children, to define key discriminative criteria, and to create an NBO diagnostic score (NBODS).
UNASSIGNED: The retrospective multicenter cohort study included clinical, laboratory, and instrumental information about histologically confirmed NBO (n = 91) and BO (n = 31). The variables allowed us to differentiate both conditions used to construct and validate the NBO DS.
UNASSIGNED: The main differences between NBO and BO are as follows: onset age-7.3 (2.5; 10.6) vs. 10.5 (6.5; 12.7) years (p = 0.03), frequency of fever (34.1% vs. 90.6%, p = 0.0000001), symptomatic arthritis (67% vs. 28.1%, p = 0.0001), monofocal involvement (28.6% vs. 100%, p = 0.0000001), spine (32% vs. 6%, p = 0.004), femur (41% vs. 13%, p = 0.004), foot bones (40% vs. 13%, p = 0.005), clavicula (11% vs. 0%, p = 0.05), and sternum (11% vs. 0%, p = 0.039) involvement. The following four criteria are included in the NBO DS: CRP ≤ 55 mg/l (56 points), multifocal involvement (27 points), femur involvement (17 points), and neutrophil bands ≤ 220 cell/μl (15 points). The sum > 17 points allowed to differentiate NBO from BO with a sensitivity of 89.0% and a specificity of 96.9%.
UNASSIGNED: The diagnostic criteria may help discriminate NBO and BO and avoid excessive antibacterial treatment and surgery.

The aim of this single-center observational study was to analyze the applicability of various imaging studies to the diagnosis and further evaluation of patients with chronic recurrent multifocal osteomyelitis (CRMO). The analysis included the data of 10 patients with CRMO treated between 2016 and 2021. The mean ages of the patients at the first manifestation of CRMO and ultimate diagnosis were 10 years and 7 months and 11 years and 10 months, respectively. Conventional radiography demonstrated focal loss of bone density in only 30% of the patients. Computed tomography showed disseminated foci with non-homogeneous osteolytic/osteosclerotic structure, with a massive loss of cortical layer and strong periosteal reaction. On magnetic resonance imaging (MRI), most patients presented with multifocal hypodense areas on T1-weighted images, with the enhancement of signal on T-weighted and STIR sequences. The duration of follow-up varied between 3 months and 3 years. In 40% of the patients, both clinical symptoms and the abnormalities seen on MRI resolved completely, whereas another 50% showed partial regression of clinical and radiological manifestations. MRI findings, co-existing with characteristic clinical manifestations, play a pivotal role in establishing the ultimate diagnosis of CRMO. MRI can also be used to monitor the outcomes of treatment in CRMO patients.

Chronic non-bacterial osteomyelitis (CNO) is a group of immune-mediated diseases which appears in bone inflammation, destruction and some orthopaedic consequences, especially in the cases of spinal involvement. This study is to compare characteristics and treatment outcomes of CNO patients with spinal involvement. The retrospective cohort study included data from 91 pediatric patients with CNO. The diagnosis is based on Jannson\'s criteria with morphological confirmation (nonspecific chronic inflammation). Spine involvement detected by X-ray, computed tomography, magnetic resonance imaging, and bone scan in 29 (31.9%) patients. No differences in the family history, concomitant immune-mediated diseases between spinal (SpCNO) and peripheral (pCNO) forms of CNO have been revealed. Only 5 (10.2%) SpCNO patients (10.2%) had monofocal monovertebral involvement. The main risk factors of spinal involvement were female sex: RR = 2.0 (1.1; 3.9), sensitivity (Se) = 0.66, specificity (Sp) = 0.6; multifocal involvement: RR = 2.1 (0.9; 5.0), Se = 0.83, Sp = 0.37; no foot bones involvement: RR = 3.1 (1.3; 7.5), Se = 0.83, Sp = 0.5; sternum involvement RR = 2.3 (1.3; 4.1), Se = 0.24, Sp = 0.94. In the linear regression analysis only female sex (p = 0.005), multifocal involvement (p = 0.000001) and absence of foot bones involvement (p = 0.000001) were independent risk factors of spinal involvement (p = 0.000001). The response rate on bisphosphonates and tumor necrosis factor-a inhibitors was 90.9% and 66.7%, consequently. Only 4/29 (13.8%) SpCNO patients underwent surgery due to severe spinal instability or deformities. The spinal involvement is frequent in CNO and could be crucial for choosing a treatment strategy. Bisphosphonates and TNFa-inhibitors could be effective treatment options for severe SpCNO.

Chronic nonbacterial osteomyelitis (CNO) is a sterile inflammatory bone disorder with an unpredictable disease course. The objective was to assess clinical and radiological disease activity in children with CNO including response to early-onset pamidronate treatment.
A single-center retrospective study was conducted of children fulfilling the Bristol Criteria for CNO. At the time of diagnosis, whole-body magnetic resonance imaging (WB-MRI) or local MRI was performed to assess radiological disease activity. Children with multifocal or spinal bone inflammation and clinical disease activity not responding to nonsteroidal antiinflammatory drugs were categorized as having extended CNO. Clinical disease activity was assessed annually.
Fifty-one children were included. Median followup time was 4 years (interquartile range 3-7). Children categorized with extended CNO (n = 32) were treated in an early-onset 2-year pamidronate regimen. In extended CNO, WB-MRI was performed at time of diagnosis, and at years 1 and 2 in 88%, 84%, and 91% of cases, respectively. During the first year, the total number of radiologically active lesions and number of spinal lesions per patient declined (p = 0.01). Clinically inactive disease was recorded in 12/32 children (38%). However, 8/12 children (67%) experienced clinical relapse. In limited CNO (n = 19), 10/19 children (53%) presented with clinically inactive disease after 1 year and did not experience clinical relapse.
Pamidronate might contribute to improvement in clinical and radiological disease activity in extended CNO, especially after 1 year of treatment. However, children with continuously active disease after 2 years of pamidronate treatment were seen.