Chronic nonbacterial osteomyelitis/Chronic recurrent multifocal osteomyelitis

What it is

From: Orphanet

Chronic nonbacterial osteomyelitis (CNO), also known as chronic recurrent multifocal osteomyelitis (CRMO), is a chronic autoinflammatory syndrome that is characterized by multiple foci of painful swelling of bones, mainly in the metaphyses of the long bones, in addition to the pelvis, the shoulder girdle and the spine.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Bone pain · Very frequent (99-80%)

An unpleasant sensation characterized by physical discomfort (such as pricking, throbbing, or aching) localized to bone.

Hyperostosis · Very frequent (99-80%)

Excessive growth or abnormal thickening of bone tissue.

Osteomyelitis · Very frequent (99-80%)

Osteomyelitis is an inflammatory process accompanied by bone destruction and caused by an infecting microorganism.

Abnormal metaphysis morphology · Frequent (79-30%)

An abnormality of one or more metaphysis, i.e., of the somewhat wider portion of a long bone that is adjacent to the epiphyseal growth plate and grows during childhood.

Abnormal vertebral morphology · Frequent (79-30%)

An abnormality of one or more of the vertebrae.

Abnormality of epiphysis morphology · Frequent (79-30%)

An anomaly of epiphysis, which is the expanded articular end of a long bone that developes from a secondary ossification center, and which during the period of growth is either entirely cartilaginous or is separated from the shaft by a cartilaginous disk.

Arthritis · Frequent (79-30%)

Inflammation of a joint.

Craniofacial osteosclerosis · Frequent (79-30%)

Abnormally increased density of craniofacial bone tissue.

Edema · Frequent (79-30%)

An abnormal accumulation of fluid beneath the skin, or in one or more cavities of the body.

Elevated circulating C-reactive protein concentration · Frequent (79-30%)

The concentration of C-reactive protein in the blood circulation is above the upper limit of normal.

Elevated erythrocyte sedimentation rate · Frequent (79-30%)

An increased erythrocyte sedimentation rate (ESR). The ESR is a test that measures the distance that erythrocytes have fallen after one hour in a vertical column of anticoagulated blood under the influence of gravity. The ESR is a nonspecific finding. An elevation may indicate inflammation or may be caused by any condition that elevates fibrinogen.

Fatigue · Frequent (79-30%)

A subjective feeling of tiredness characterized by a lack of energy and motivation.

Osteolysis · Frequent (79-30%)

Osteolysis refers to the destruction of bone through bone resorption with removal or loss of calcium.

Poor appetite · Frequent (79-30%)

A reduced desire to eat.

Other findings in the same source

From: Orphanet

Additional reported features include Weight loss (Frequent (79-30%)); Abnormality of the sacroiliac joint (Occasional (29-5%)); Acne (Occasional (29-5%)); Anemia (Occasional (29-5%)); Fever (Occasional (29-5%)); Inflammation of the large intestine (Occasional (29-5%)); Palmoplantar pustulosis (Occasional (29-5%)); Pruritus (Occasional (29-5%)); Psoriasiform dermatitis (Occasional (29-5%)); Scoliosis (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adolescent; Childhood

Inheritance in the source

From: Orphanet

Not applicable

Frequency and the population described

From: Orphanet

Point prevalence: 1-9 / 1 000 000; Worldwide; Value and class. Annual incidence: 1-9 / 100 000; Worldwide; Value and class.

Which doctor should you see?

The suggested department for discussing Chronic nonbacterial osteomyelitis/Chronic recurrent multifocal osteomyelitis is Rheumatology, with a rheumatologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Are the findings inflammatory, structural or due to another mechanism?
• Is there evidence that other organs need assessment?
• How will function and any treatment-related risks be monitored?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Chronic nonbacterial osteomyelitis/Chronic recurrent multifocal osteomyelitis. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.