Chronic Recurrent Multifocal Osteomyelitis (CRMO)

Chronic recurrent multifocal osteomyelitis

Fast Facts

  • Chronic recurrent multifocal osteomyelitis (CRMO), or chronic nonbacterial osteomyelitis (CNO), is a disorder that causes bone pain due to inflammation in the bones not caused by infection.
  • One or multiple bones can be affected.
  • Treatment usually starts with NSAID medications (ibuprofen, naproxen, meloxicam) but some patients need stronger medicines, including methotrexate, biologics (etanercept, adalimumab, infliximab, anakinra) and bisphosphonates (pamidronate, zoledronic acid).
  • Studies have shown a 40% remission rate (no active disease after 1 to 5 years of treatment), but 50% recurrence within 2 years, so close follow-up is needed.

Chronic recurrent multifocal osteomyelitis (CRMO) can take months to years to diagnose. CRMO was previously thought to be rare, occurring in about 0.4 out of 100,000 people per year. As recognition of CRMO is increasing, it appears to be more common than that. In fact, CRMO may be nearly as common as bone infections. The average age that CRMO starts is 9 to 10 years. More girls are affected than boys.

What Causes it?

CRMO is an auto-inflammatory disorder, meaning the immune system attacks the bones causing inflammation, even though there is no infection. A small fraction of people with CRMO have a genetic component. Some families have more than one person with CRMO.

What are the Common Symptoms?

Bone pain is the most common symptom. There is usually tenderness at the affected site (it hurts to be pushed on). The pain can cause the person to avoid using the affected body part. Some people with CRMO can develop arthritis (joint swelling). Fatigue is common during active disease.

How is it Diagnosed?

Diagnosis is based on exam, imaging (such as x-rays, bone scan or MRI), bone biopsy, and laboratory (blood) tests. Lab tests are normal in most people, but can show anemia (blood doesn’t carry enough oxygen through your body) and elevated markers of inflammation (ESR, CRP) in others. Bone that has been altered or damaged can be seen on x-ray, bone scan and MRI. MRI is the most sensitive type of imaging to find signs of CRMO. Bone biopsy may be needed to rule out infection or cancer. The biopsy in CRMO usually shows acute (short-term) or chronic (long-term) inflammation.

How is it Treated?

Treatment of CRMO depends on how severe it is and which bones it affects. Some people respond to non-steroidal anti-inflammatory medications (NSAIDs), such as naproxen, meloxicam or indomethacin. These medications can cause stomach upset and easy bruising. People on these medications long-term should have lab monitoring for liver and kidney function.

People with continued pain and active bone lesions can require stronger immunosuppressive medications, such as methotrexate. Methotrexate can cause nausea and requires regular lab monitoring. It can be dangerous in people who drink alcohol and can cause birth defects if taken during pregnancy.

Additional treatment options include biologic medications, such as etanercept, adalimumab or anakinra, which are injectable medications, or infliximab, which is an IV infusion. Methotrexate and biologic medications are immunosuppressive. People taking these medicines are at an increased risk of infection and should be evaluated by a doctor if they develop fever or symptoms of infection. People must be screened for tuberculosis (TB) prior to starting biologic medications.

Bisphosphonates such as pamidronate and zoledronic acid are another type of treatment for CRMO. These medicines are IV infusions used to treat bone conditions such as osteoporosis. Bisphosphonates can cause flu-like symptoms for a few days after the infusion.

Monitoring of Disease Activity

CRMO is monitored by following symptoms and imaging studies. MRI is the best way to assess resolution of active bone lesions and/or detect new lesions.

Living with CRMO

For people with CRMO, life often involves taking medications and having follow-up visits with a rheumatologist. Depending on which bones are affected, some people need to limit activities to prevent serious injury or bone damage. People with spine involvement are at risk for serious injury if spine fracture occurs. People with CRMO should discuss activity restrictions with their doctor.

It is possible for CRMO to go away either for a short period of time or permanently in some people. For others, even though CRMO is controlled, chronic pain (amplified musculoskeletal pain) that does not respond to medications can develop. This type of pain may require treatment in a pain clinic.

Updated December 2021 by the American College of Rheumatology Committee on Communications and Marketing.

This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.

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