Chronic recurrent multifocal osteomyelitis: review.

Objective Chronic recurrent multifocal osteomyelitis (CRMO) is primarily a disorder of children and adolescents characterized by episodic osseous pain over several years. The objective of this article is to present an overview of this entity with an emphasis on imaging manifestations. Conclusion CRMO can be a difficult diagnosis, often with nonspecific imaging findings. The critical factors leading to its diagnosis are patient demographics, clinical course, and distribution. However, a greater understanding of the imaging appearance during both active and reparative phases may lead to improved detection. Introduction Chronic recurrent multifocal osteomyelitis (CRMO) is a skeletal disorder of unknown cause, occurring primarily in children and adolescents. The entity was first described by Giedion et al. [1] in 1972 as "an unusual form of multifocal bone lesions with subacute and chronic symmetrical osteomyelitis." Later, Bjorksten and Boquist [2] noted its association with pustulosis palmoplantaris and developed the term "chronic recurrent multifocal osteomyelitis." Between 200 and 300 cases of CRMO have been reported in the literature worldwide, consisting mainly of case series with relatively brief follow-up durations [3]. However, because of increasing disease awareness and longer clinical observation periods, this disorder is likely more common than previously realized. CRMO is a diagnosis of exclusion based on the following criteria: lack of causative organism; no abscess formation, fistula, or sequestra; atypical location compared with infectious osteomyelitis, with frequent involvement of the clavicle and often showing multifocality; radiographic appearance of subacute or chronic osteomyelitis; nonspecific histopathologic and laboratory findings compatible with subacute or chronic osteomyelitis; characteristic prolonged, fluctuating course with recurrent episodic pain over several years; and accompanying pustulosis palmoplantaris or acne [2, 4]. Clinical Findings CRMO is characterized by the insidious onset of pain and swelling corresponding to the involved bones [5, 6]. Most cases (up to 85%) occur in females, with a median age of onset of 10 years [7, 8]. The disease course is typically prolonged over several years. punctuated by periodic exacerbations. Symptoms may either recur at sites affected previously or involve new areas with subsequent flare-ups. Patients may experience concomitant systemic symptoms including low-grade fevers and generalized malaise [9]. CRMO may be accompanied by many skin disorders, most commonly pustulosis palmoplantaris, that may recur along with the osseous exacerbations [2, 5, 10]. The lesions are predominantly situated in the metaphyses of tubular bones, followed by the clavicle and spine [2, 6, 11-13]. Within tubular bones there is a predilection for the lower extremities, with the distal femur, proximal tibia, distal tibia, and distal fibula most commonly affected [14]. The disease may less frequently involve the ribs [10, 12, 15-17], sternum [15], and pelvis [18]. Symmetric involvement is common [14], and multifocality is virtually always present. The clinical course of CRMO may last anywhere from 7 to 25 years [3, 11, 19]. Treatment generally involves antiinflammatory agents targeting symptomatic relief, particularly nonsteroidal antiinflammatory drugs (NSAIDs) [20]. NSAIDs are usually effective in symptomatic relief, with response rates of up to 80% [7, 21].