Chronic recurrent multifocal osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is an idiopathic inflammatory bone disorder seen primarily in children and adolescents. It is often a diagnosis of exclusion once underlying infection and neoplasia has been ruled out. However, there are some cases in which lesion location and morphology combined with clinical assessment can yield a diagnosis without biopsy.

Epidemiology

There is a female predominance, with 85% of cases reported in women. 

Clinical presentation

The typical clinical picture of CRMO is a child or young adult with a history of chronic multifocal bone pain. Systemic symptoms of fever, weight loss or lethargy are uncommon but can occur. Biopsy of osseous lesions shows an inflammatory reaction with failure to culture any organisms.

Pathology

The aetiology and pathogenesis of CRMO remains unclear. While early reports suggested an infective aetiology, no consistent pathogen has been demonstrated in subsequent studies and biopsy cultures are usually negative. 

As the condition can be associated with skin conditions, like psoriasis, or inflammatory bowel disease an autoimmune cause is thought likely. 

Radiographic features

The most common sites of disease are the metaphyses or metaphyseal equivalents of the long bones, most frequently in the tibia. However, a wide range of skeletal site involvement has been reported.

Clavicle involvement is a characteristic finding since this is an uncommon location for haematogenous osteomyelitis. However, imaging findings overall remain suggestive rather than pathognomonic for CRMO.

Plain radiograph

Initially to examine the symptomatic site:

• early stages: osteolytic lesion
• later stages: progressive sclerosis ³

Lesions can range between purely osteolytic, osteolytic with a sclerotic rim, mixed lytic and sclerotic, and purely sclerotic.

MRI

Useful for determining the extent of disease with whole-body STIR, including disease sites that may be clinically occult and can be used for subsequent follow-up. Findings can include:

• bone marrow oedema
• periostitis
• soft tissue oedema
• extension across the physis
• areas of post-gadolinium enhancement

Findings that should raise the possibility of haematogenous osteomyelitis over CRMO include:

• large fluid collection
• abscess
• fistulous tract
• bony sequestrum

Nuclear medicine

Similar to whole-body MRI, bone scintigraphy demonstrates multifocal uptake in keeping with the multifocal nature of the disease. In children, MRI is preferred to avoid radiation dose.

Treatment and prognosis

CRMO should be treated by a rheumatologist. While non-steroidal anti-inflammatory drugs may cause some symptomatic relief, there is often the need for a greater degree of immunosupression and possibly biological agents. These are often similar drugs that are used in the treatment of juvenille arthritis and the associated multi-disciplinary rheumatology team is vital to ensure adequate physiotherapy input.

Long-term clinical follow up with whole-body MRI may be needed until the patient is in radiological remission or a steady state is achieved.

Differential diagnosis

• infectious osteomyelitis (subacute and chronic)
• Langerhans cell histiocytosis
• Ewing sarcoma

History and etymology

The syndrome of CRMO was originally described in 1972 in four children under the name “subacute and chronic recurrent osteomyelitis'' ¹. The term chronic recurrent multifocal osteomyelitis was first used by Probst et al ².