Background: Chronic recurrent multifocal osteomyelitis (CRMO) is a rare inflammatory disease characterized by multiple sterile bone lesions that typically involve the metaphysis of the long bones and the axial skeleton. Association of CRMO with Inflammatory Bowel Diseases (IBD), has been reported in some cases. However, still little is known about the topic.

Objectives: to evaluate the characteristics of CRMO patients with IBD (C-IBD) in comparison to CRMO patients without gastrointestinal disease, in order to describe their clinical, serological and radiological characteristics and response to treatments.

Methods: Patients with CRMO and C-IBD were retrospectively enrolled in the Eurofever Registry. The clinical, serological and radiological characteristics of the C- IBD (Crohn’s disease (CD), ulcerative colitis (UC), U-IBD (undifferentiated IBD), and of CRMO patients were reviewed.

Results: 12 patients with C-IBD were compared to 36 CRMO patients. In the C-IBD cohort, 83.3% of patients were male, and in 91.6% of cases the disease onset was characterized by CRMO symptoms, while in one case osteoarticular and GI symptoms were simultaneous. The mean age at onset of osteoarticular manifestation was 10.38 years, and at IBD onset was of 10.9 years. In the CRMO cohort, 61% of patients were female, with a mean age at disease onset of 9.16 years. All the CRMO and C-IBD patients presented a metaphyseal involvement of the long bones of the lower limbs, while upper limbs were involved in 33.3% and 41.6% of C-IBD and CRMO patients respectively. Pelvic involvement was equally present in the 2 groups (66% in C-IBD and 55.5% in CRMO), while sacroiliitis was more prevalent in the C-IBD group (41.6 %vs 13.8%) and vertebral involvement in the CRMO group (52% vs 25%). In the C-IBD cohort, IBD symptoms were present in 58.3 % of patients (n=7) and were characterized by abdominal pain (n=3), diarrhoea (n=5), haematochezia and weight loss (n=2). 8 patients presented CD, 1 patient UC and 3 IBD-U. All C-IBD patients presented an elevation of the fecal calprotectine, while hemoccult was positive in 8 patients. Abdominal US showed a bowel thickening in 58.3% of patients (n=7). 75% of patients (n=9) presented a microcytic anemia, which was present also in 36% of the CRMO group. All patients in the C-IBD group presented a CRP and ESR elevation at disease onset and after treatment was started, and this represented the main difference with the CRMO group, in which CRP was elevated in 44% of patients at disease onset and normalized few-weeks after the treatment was started. In the C-IBD group, at disease onset all patients underwent a therapy with NSAIDS, associated in 2 cases to steroids, while 1 patient was started on methotrexate (MTX) and 1 on etanercept. After IBD was diagnosed, the majority of patients underwent an oral steroid course, 50% (n=6) were started on salazopyrin (SAL), which resulted efficacious in half of patients; 33% (n=4) responded to Adalimumab (ADA) alone, while 41,6% (n=5) achieved remission under the combination ADA+MTX. In the CRMO group, 91.6% of patients received initially NSAIDS (efficacious in 14%), 58.3% (n=21) received SAL (efficacious in 19% of patients), while 38% were treated with MTX (efficacious in 40%), and 36% (n=13) received bisphosphonates, which had a positive effect in 38.5%. In 25% (n=9) of patients a steroidal course was needed, while biologics were added in 27.7% of patients (MTX + ADA being the most frequent combination, 19.4%).

Conclusion: This represents the largest cohort of IBD associated to CRMO reported in the literature, highlighting a possible underdiagnosis of this condition. The persistence of an inflammatory state despite the therapies, and the presence of microcytic anemia resulted to be associated with the development of an IBD. Seen the frequent absence of intestinal symptoms, we suggest a screening with fecal calprotectin in all CRMO patients at disease onset and during follow-up, especially in those patients that present a persistent elevation of inflammatory parameters.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: Caterina Matucci-Cerinic: None declared, Chiara Longo: None declared, Roberta Caorsi: None declared, Alessandro Consolaro: None declared, Silvia Rosina: None declared, Stefano Volpi SOBI, Nicolino Ruperto Abbvie, Aclaris, Amgen, AstraZeneca, Aurinia, BMS, Boehringer Ingelheim, Eli Lilly, Galapagos, Guidepoint, Janssen, Novartis, Pfizer, Sanofi., Abbvie, Aclaris, Amgen, AstraZeneca, Aurinia, BMS, Boehringer Ingelheim, Eli Lilly, Galapagos, Guidepoint, Janssen, Novartis, Pfizer, Sanofi., Serena Arrigo: None declared, Marco Gattorno Novartis, SOBI, Clara Malattia: None declared.