The Many Faces of Pediatric Chronic Recurrent Multifocal Osteomyelitis ( CRMO) : A Practical Location‐ and Case‐Based Approach to Differentiate CRMO From Its Mimics

To define non-bacterial osteitis (NBO) as a clinical entity possibly associated with autoimmune manifestations. Patients with sterile osteitis were analysed to develop diagnostic criteria. A total of 89 patients with non-bacterial inflammatory bone lesions were observed for a median of 49 months. History, diagnostic imaging, laboratory and histological data were obtained. Mutation analysis in the genes PSTPIP1 and PSTPIP2 was performed. Patients had an onset of disease at a median age of 10 yrs [interquartile range (IQR) 7.5-12] and suffered a median period of 21 (IQR 9-52) months with a median of three foci per patient. Twenty percent of all the patients demonstrated associated autoimmune disorders, particularly of the skin and bowel. The majority of bone lesions were located in the vertebrae and metaphyses. Slight-to-moderate elevation of inflammation values were found in all the patients and antinuclear antibodies were elevated in 30%. Non-steroidal anti-inflammatory drugs (NSAIDs) were effective in 85% of the patients. HLA-B27 and Human Leukocyte Antigen-DR (HLA-DR)-classification did not differ from the general population. Autoimmune diseases in 40% of all the families, multiply affected family members, linkage to 18q21 and mouse models strongly indicate a genetic basis for NBO. We observed three different courses of disease regarding the duration of complaints, rate of complications and associated autoimmune manifestations leading to a new classification of NBO. Clinical analysis of our cohort leads us to define NBO as a distinct disease entity with three clinical presentations: acute NBO, chronic recurrent multifocal osteomyelitis or persistent chronic NBO. Diagnostic criteria were proposed to differentiate NBO from diseases with similar clinical presentation.

Purpose of Review Chronic non-bacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder. We summarize the clinical presentation, diagnostic approaches, most recent advances in understanding the pathophysiology, and available treatment options and outcomes in CNO/CRMO. Recent Findings Though the exact molecular pathophysiology of CNO/CRMO remains somewhat elusive, it appears likely that variable defects in the TLR4/MAPK/inflammasome signaling cascade result in an imbalance between pro- and anti-inflammatory cytokine expressions in monocytes from CNO/CRMO patients. In this context, we present previously unpublished data on cytokine and chemokine expression in monocytes and tissues. Summary CNO/CRMO is an autoinflammatory bone disorder resulting from imbalanced cytokine expression from innate immune cells. Though the exact molecular pathophysiology remains unclear, variable molecular defects appear to result in inflammasome activation and pro-inflammatory cytokine expression in monocytes from CNO/CRMO patients. Recent advances suggest signaling pathways and single molecules as biomarkers for CNO/CRMO as well as future treatment targets.

Background Chronic recurrent multifocal osteomyelitis (CRMO) is a little known inflammatory bone disease occurring primarily in children and adolescents. Delays in referral and diagnosis may lead to prolonged courses of antibiotics with in-patient care, unnecessary radiation exposure from multiple plain radiographs or bone scans and repeated surgery including bone biopsies. Children (aged < 18 years) diagnosed with CRMO between January 2005 and December 2012, reviewed at Bristol Royal Hospital for Children were included and all available data collected. Information regarding CRMO was sent to all orthopaedic surgeons in the region in 2009. The aim of the study was to examine the features of the cohort, to examine the length of time to diagnosis and to explore the criteria used for diagnosis with and without biopsy. Findings Over an 8 year period, 41 patients were diagnosed with CRMO. Symptom onset occurred at a median of 9 years of age and time to diagnosis had a median of 15 months (range 0–92). Correlation coefficient analysis for time to diagnosis by year showed statistical significance with a decreasing trend. From the cohort data, diagnostic criteria were developed; applied retrospectively, 34 (83 %) children may have been diagnosed using the criteria, without a biopsy. Conclusions The data suggest that increasing knowledge of this condition may shorten time to diagnosis. Use of the Bristol diagnostic criteria by an experienced clinician may obviate the need for biopsy in some patients.