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May 14, 2006
Chronic recurrent multifocal osteomyelitis (CRMO)
by SirGan
 Chronic recurrent multifocal osteomyelitis (CRMO) is one rare condition in which a child’s bones become inflamed and painful. Important thing is that this condition is not caused by an infection but in other ways the symptoms are very similar to osteomyelitis, which is caused by an infection.CRMO comes and goes, which means there are periods where there are no symptoms but some exacerbations occur occasionally. These are periods of remission and exacerbation. It primarily affects the skeletal system although; some ‘extra-skeletal’ sites can be affected. The commonest sites are metaphyses of long bones, spine, pelvis, and shoulder girdle. Even though this disease has been recognized as a clinical entity for almost three decades now, its origin and pathogenesis are not entirely clear.
The clinical and radiological features on the disease are variable and the diagnosis can be difficult.
Multiple names have used to describe this entity and some of these include
Incidence of the conditionThis disease is rare, and often affects children, more commonly girls than boys, with a sex ratio of five to one. But, these in no rules concerning patient age because adults can also be affected. The peak age of incidence is around 10 years, with the range being four to 14 years. No epidemiological data on incidence and prevalence have been published so far. However, incidence might be estimated at 1:1,000,000.
What are the common symptoms?Chronic recurrent multifocal osteomyelitis is one disorder that damages the affected area of bone and creates characteristic formations also known as bone lesions. Problem is that, when these lesions flare-up they cause
The pain can be quite severe and may limit your child’s activities. Because the pain can be so bad – not only that it can stop the patient from going to school, but sometimes- they might have to stay in hospital for treatment with medicines. It affects mainly the metaphyses of the long bones, in addition to the spine, the pelvis and the shoulder girdle. Some bones seem to be more affected by CRMO than others and these include the shinbone, thighbone and clavicle (collarbone). Many young people with CRMO have pain in more than one area of bone.
Possible cause of CRMOThe cause of this condition is unknown, despite intensive investigation over a period of more than 30 years. Carefully done culture and tissue sampling on bone lesions in children with this disease, using the best available techniques, have failed to yield any apparent infectious agents.
The main suggestions for possible causes include:
Propionibacterium acnes has been postulated to be involved in the pathogenesis. However, in larger cohorts and by using state of the art microbial techniques no apparent infectious agents could be detected at the site of the bone lesion in pediatric patients.
There are also some experts that believe it is an inherited condition and that genetics play a major role in developing this condition. They have found a significant association of CRMO with a rare allele of marker D18S60, resulting in a haplotype relative risk (HRR) of 18.
This suggests the existence of a gene in this region contributing in a significant manner to the etiology of CRMO and concomitantly demonstrates evidence for a genetic basis of CRMO for the first time. This gene is different from RANK, which is mutated in familial expansile osteolysis (FEO), but not in CRMO.
Differential diagnosisThe differential diagnosis includes
Some experts have named some precise criteria for diagnosis of this condition:
Clinical manifestationsSkeletal manifestations
Other organ involvement
Diagnosis of chronic recurrent multifocal osteomyelitisClinical diagnosis in affected children can be difficult because the clinical picture and course of disease may vary significantly. CRMO can have similar symptoms to other conditions, like arthritis. Radiological and magnetic resonance imaging features of CRMO have been described, but differential diagnosis remains difficult, including rheumatic diseases, bacterial osteomyelitis, and malignancy. To get a diagnosis the person needs to have a series of tests and scans.
Treatment of chronic recurrent multifocal osteomyelitisThe effective and definite treatment is still impossible. The aim of treatment is to try to prevent flare-ups and treat them if they occur. Long term treatment is usually required to monitor any growth disturbances in the affected bones.
Disease course and prognosisThe long term outcome of CRMO is poorly understood. Long term sequelae include
Most children with CRMO go into remission in late childhood, but some have relapses in late teenage or early adulthood. However, if certain areas of bone are affected, this could mean the limb does not develop, as it should, leaving one limb shorter than the other. This can be treated in various ways including surgically. Although children and young people with CRMO may need to miss some schooling due to their illness, most grow up to lead normal lives, working and raising a family.
Recently, evolvement of CRMO into arthritis or spondyloarthropathy has been documented in several cohort studies of children and young adults. Inflammatory joint involvement already at the time of diagnosis and during the course of the disease might have been underestimated so far. Pathogenetically, CRMO is linked to juvenile arthritis and features of CRMO can overlap features of enthesitis-related arthritis or psoriatic arthritis.
The bottom line is that- overall, the outlook for children and young adults with CRMO is excellent. The majority respond well to treatment and suffer few long-term effects.
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