What Is Chronic Recurrent Multifocal Osteomyelitis (CRMO)?

Medically Reviewed by Dan Brennan, MD on July 23, 2022
Written by Alyssa Anderson
5 min read

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoimmune disease. Autoimmune diseases are conditions where your immune system attacks your own body instead of foreign pathogens like viruses and bacteria. In the case of CRMO, your immune system attacks one or more bones in your body.  

CRMO is a severe form of chronic nonbacterial osteomyelitis (CNO). 

The exact cause of CRMO remains unknown. The condition doesn’t involve any bacterial infections or other understood causes that would naturally trigger an immune response.

There does seem to be some genetic component to the disease. The exact genes involved are not properly understood, but there are cases where multiple family members have the condition. We need more research to better understand any potential environmental and genetic causes.

CRMO isn’t a type of cancer, but it can have similar symptoms to certain types of bone cancer.  

CRMO most commonly affects children and young adults. On average, people are diagnosed when they’re around 9 or 10 years old. Females tend to develop this condition more often than males. 

The condition is not extremely common, but rates may be higher than researchers originally thought. Early estimates found that CRMO occurred at a rate of 0.4 cases per 100,000 people. But numbers of diagnoses are going up as more doctors and patients become aware of this condition. 

Data suggests that the condition may be as frequent as bone infections. Bone infections are seen in greater amounts of the population than any early estimates could have predicted for CRMO. 

CRMO can affect one or more bones. It most commonly affects the long bones in a child’s legs. It also occurs in a child’s pelvis and spine more commonly than in other bones. But keep in mind that CRMO can flare up anywhere. 

CRMO symptoms include: 

  • Pain. This is the most common CRMO symptom.
  • Joint inflammation. This is essentially arthritis in the joints near your child’s affected bones. It can be a major cause of pain. 
  • Bone deformities. This condition can cause problems with your child’s growth plates. Growth plates are the parts of the bone that lengthen as your child ages. The amount of abnormal growth can vary from person to person. For example, your child’s legs could end up two different lengths. 
  • Slowed growth. Even when there isn’t any pain, your child’s joints may not grow as much as they should. 
  • Fatigue. Your child will likely be tired when their symptoms flare up. 
  • Increased risk of fracture. Depending on the location of your child’s CRMO, certain activities can make broken bones particularly dangerous. This can lead to serious complications if the damage occurs to your child’s spine, including the risk of paralysis. 

CRMO symptoms can come and go while your child is growing up. Once your child’s doctor has found an appropriate treatment, the condition will likely go into a period of remission. This is when the inflammation and other symptoms are gone. But symptoms can return at any time even once your child has gone into remission. They’re more likely to return after the treatment stops. 

Your child will need a complete medical examination to help diagnose this condition. This condition is rare and not well-known. The average time that it takes to diagnose the condition is 15 months. This lengthy period can lead to longer treatment durations and the need for in-patient options. 

Your doctor will likely use several tests to help them arrive at your child’s CRMO diagnosis. These tests may include: 

  • Imaging tests
  • Blood tests
  • Genetic tests 

Currently, there isn’t a cure for CRMO. Instead, treatment focuses on managing your child’s symptoms. The U.S. Food and Drug Administration (FDA) hasn’t approved any medications to specifically treat CRMO. Any medications that your doctor recommends have been studied in the context of similar or related conditions.

Potential treatment methods include: 

  • Nonsteroidal anti-inflammatory drugs (NSAIDs). These tend to be the first type of medication that your doctor will try to treat your child’s symptoms. Ibuprofen is a common example. About 50% of children respond well to this type of medication. Your doctor needs to carefully monitor your child’s liver and kidneys if they take this kind of medication for a long time. 
  • Disease-modifying antirheumatic drugs (DMARDs). These are for children that need stronger medications outside of inflammation and pain management. There’s a wide variety of medications that fall into this category. Some can weaken your immune system. This comes with additional complications that your doctor will consider before prescribing these medications. 
  • Lifestyle changes. Your child may not be able to use their painful limbs as much as they’d like. They may also need to adapt to fatigue and the increased risk of breaking bones. Occupational and physical therapists can help you learn how to manage your child’s condition. 

These visits are particularly necessary before your doctor or medical team makes any changes to your child’s treatment plan. 

There are a handful of conditions that are associated with CRMO. Some of these conditions are occasionally diagnosed at the same time as your child’s CRMO, while others are unexplained side effects of CRMO. These conditions include: 

  • Inflammatory bowel disease (IBS). This is another type of autoimmune condition that can co-occur with CRMO. Some treatment options can overlap with your CRMO medications. 
  • Psoriasis. This is another autoimmune condition that can affect your skin. It can co-occur with your CRMO. 
  • Amplified musculoskeletal pain. This is unexplained muscle pain that continues even after your CRMO is in remission. Unfortunately, this type of pain doesn’t respond to normal pain medications. Unique treatments are determined on a case-by-case basis. 

In 40% of cases, children go into complete remission within their first one to five years of treatment. This means that there’s no active inflammation or autoimmune response. At this time, your child’s pain and other symptoms should stop. They should be able to resume a normal, active life. 

Even once your child is in remission, they’ll require frequent monitoring. Your child will need to see a rheumatologist regularly. The exact number of visits depends on the severity of your child’s original condition and the likelihood of remission.  

These visits will likely involve additional MRI imaging to check on the health of your child’s growth plates. In 50% of cases, CRMO recurs within the first two years after treatment stops. This means that your child will need to resume a treatment routine. 

Active phases of the disease can last anywhere from months to years to the rest of your child’s life. 

Make sure to see a doctor if you have any concerns about pains that your child’s having, particularly in their legs and hip area.