Chronic recurrent multifocal osteomyelitis (CRMO)

Chronic recurrent multifocal osteomyelitis is a rare, non-infectious bone condition that mainly affects children and adolescents and is considered autoinflammatory, meaning the innate immune system drives inflammation in the bone without any infection present. Despite the word osteomyelitis, which usually means a bone infection, cultures in CRMO are sterile and antibiotics do not resolve it. Research describes three main proposed mechanisms behind the disease: imbalanced cytokine signaling from innate immune cells, increased activation of the inflammasome, and enhanced activity of the bone-resorbing cells called osteoclasts, occurring without the autoantibodies or antigen-specific T cells seen in classic autoimmune disease.

It tends to follow a waxing and waning course that is often worse at night, and because it is rare, exact prevalence figures are not well established, though it is increasingly recognized as clinicians become more familiar with its imaging pattern. The main symptom is bone pain, often with swelling and tenderness, most commonly in the long bones, collarbone, spine, pelvis, or jaw, and some children also have related skin or gut inflammation.

Common signs

Bone lesions often appear in more than one site, sometimes together and sometimes emerging at new spots months or years apart. Children may limp, avoid using an affected limb, or run low fevers during flares. Roughly 1 in 10 also develop palmoplantar pustulosis, psoriasis, severe acne, or inflammatory bowel disease as a related condition.

This is a plain-language summary for orientation, not a diagnosis. Mechanisms are described as current understanding, not settled fact. Work with your own clinician for your care.