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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Radiology

Diagnostic Imaging and Tests

At a Glance

SAPHO syndrome is diagnosed by combining symptoms with imaging and, when needed, a bone biopsy to rule out infection or cancer. CRP and ESR can be normal, MRI findings are not specific, and a missing bull’s-head sign does not exclude SAPHO.

Diagnosing SAPHO or Adult Chronic Nonbacterial Osteitis (Adult CNO) is often a process of assembling clinical clues and eliminating other possibilities [1]. Because the symptoms can look like many other conditions, doctors use a combination of blood tests, advanced imaging, and sometimes a biopsy to build a “map” of what is happening inside your bones [2].

Why Blood Tests Are Often Normal

One of the most frustrating parts of a SAPHO diagnosis is having severe pain while your blood tests come back “normal” [1].

  • Inflammatory Markers: Tests like CRP (C-reactive protein) and ESR (sedimentation rate) measure general inflammation in the body. While these may rise during a major flare, they are frequently normal in many SAPHO patients. Furthermore, pain, clinical function, and inflammatory markers do not always change together [3][1][4].
  • Genetic Testing: HLA-B27 is a genetic marker often linked to other types of arthritis (like ankylosing spondylitis). In SAPHO, this marker is usually negative or “unremarkable,” meaning it cannot be used to confirm the diagnosis [5][6].
  • No “Smoking Gun”: There is currently no single blood test that can “prove” you have SAPHO. The diagnosis depends much more on how your clinical symptoms align with what your doctor sees on imaging [3].

The Role of Imaging

Different types of scans show different parts of the disease. The choice of imaging depends on your symptoms and what conditions need to be ruled out [7][2].

1. MRI (A Key Tool for Activity)

MRI is highly valuable for detecting bone marrow edema—a buildup of fluid inside the bone [8].

  • However, marrow edema is nonspecific; it can also occur with infection, tumor, trauma, and mechanical stress [9].
  • Whole-Body MRI: Doctors may sometimes use this to look for “silent” areas of inflammation, though an imaging finding alone does not establish clinically active disease or automatically require treatment [10][7].

2. CT Scan (Looking at Structure)

While MRI shows fluid and inflammation, CT scans are better at showing the permanent changes to the bone structure.

  • Hyperostosis and Sclerosis: These are terms for bone that has become abnormally thick or dense [11].
  • Erosions: CT can show where the bone has been “pitted” or worn away [11].

3. Bone Scintigraphy (The “Bull’s-Head Sign”)

A bone scan involves a small amount of radioactive tracer that highlights areas of high bone activity.

  • The Bull’s-Head Sign: In some patients, the tracer accumulates in the sternum and collarbones in a shape that resembles a bull’s head with horns [12][13].
  • Note: While this sign is very characteristic of SAPHO, it is not present in every patient. You can still have the disease even if your scan does not show this specific pattern [14].

When a Biopsy Is Investigated

A bone biopsy is not required for everyone, but it can be an important tool to help exclude dangerous conditions. Current guidelines suggest that if your clinical symptoms and MRI findings are “textbook” for SAPHO, a biopsy might be avoided, but atypical lesions require careful investigation [15][16][1].

What the Biopsy Explores

If you have a biopsy, the resulting pathology report is interpreted in context [17][18]:

  1. Exclusion of Malignancy: The report helps ensure no cancerous cells are present.
  2. Microbiology (Cultures): The tissue may be tested for standard bacteria. While cultures are expected to be negative in SAPHO, false negatives can happen, and any positive result (like C. acnes) requires individualized infectious-disease input to distinguish contamination from infection.
  3. Histology: The report may describe “nonspecific” inflammatory changes, such as neutrophilic infiltration or reactive bone formation. While typical of SAPHO, these are not diagnostic on their own.

Common questions in this guide

Can I have SAPHO syndrome if my CRP and ESR are normal?
Yes. CRP and ESR measure general inflammation, but they are often normal in people with SAPHO, so normal results do not rule it out. Doctors combine blood tests with symptoms and imaging.
What can an MRI show in SAPHO syndrome?
MRI can show bone marrow edema, which is fluid and inflammation within bone. This finding is not specific to SAPHO and can also occur with infection, tumors, injury, or mechanical stress. A whole-body MRI may find areas without symptoms, but a scan alone does not prove active disease or determine the need for treatment.
What does the bull's-head sign mean on a SAPHO bone scan?
It describes tracer uptake in the breastbone and collarbones that forms a shape resembling a bull’s head. It is characteristic of SAPHO, but not every patient has it, so a missing bull’s-head pattern does not rule out the condition.
Is a bone biopsy always needed to diagnose SAPHO?
No. When symptoms and MRI findings are typical, clinicians may diagnose SAPHO without a biopsy. A biopsy may be recommended for an unusual lesion to look for cancer or infection; cultures and tissue findings must be interpreted with the rest of your evaluation.
Why might my doctor order CT as well as MRI for SAPHO?
MRI is especially useful for seeing active inflammation and bone marrow edema. CT gives a clearer view of lasting structural changes such as thickened or hardened bone and areas of erosion. Using both tests depends on your symptoms and which other conditions need to be excluded.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Why are my inflammatory markers (CRP and ESR) normal despite my level of pain?
  2. 2.Does my MRI show active bone marrow edema, and how does that affect our treatment decision?
  3. 3.If my bone scan shows a 'bull's-head' pattern, how does that fit into my overall diagnosis?
  4. 4.If you are recommending a biopsy, what specific tests (cultures or pathology) are you ordering to investigate for infection or cancer?
  5. 5.Would a whole-body MRI be useful to evaluate other areas, or is targeted imaging better for me?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    Diagnostic and therapeutic practices in adult chronic nonbacterial osteomyelitis (CNO).

    Leerling AT, Clunie G, Koutrouba E, et al.

    Orphanet journal of rare diseases 2023; (18(1)):206 doi:10.1186/s13023-023-02831-1.

    PMID: 37480122
  2. 2

    [Diagnosis and treatment of chronic nonbacterial osteitis (CNO) and SAPHO syndrome : Implications of the current consensus recommendations of an international commission of experts for German rheumatology].

    Assmann G, Klemm PCM, Hedrich C, et al.

    Zeitschrift fur Rheumatologie 2026; (85(2)):93-105 doi:10.1007/s00393-025-01741-w.

    PMID: 41313366
  3. 3

    SAPHO syndrome: current clinical, diagnostic and treatment approaches.

    Demirci Yildirim T, Sari İ

    Rheumatology international 2024; (44(11)):2301-2313 doi:10.1007/s00296-023-05491-3.

    PMID: 37889264
  4. 4

    A retrospective study of bone scintigraphy in the follow-up of patients with synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome: is it useful to repeat bone scintigraphy for disease assessment?

    Li C, Wang L, Wu N, et al.

    Clinical rheumatology 2020; (39(4)):1305-1314 doi:10.1007/s10067-019-04864-z.

    PMID: 31858336
  5. 5

    A Case of Synovitis Acne Pustulosis Hyperostosis Osteitis (SAPHO) Syndrome With Myeloperoxidase Anti-neutrophil Cytoplasmic Antibody: Exploring an Association or Coincidence.

    Kimura K, Hayashi K, Suzuki A, et al.

    Cureus 2025; (17(5)):e83866 doi:10.7759/cureus.83866.

    PMID: 40497194
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    [Genetic basis of chronic nonbacterial osteomyelitis].

    Deen Hayatu M, Hüffmeier U

    Zeitschrift fur Rheumatologie 2026; (85(2)):136-140 doi:10.1007/s00393-025-01774-1.

    PMID: 41563457
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    Expert consensus recommendations for the diagnosis and treatment of chronic non-bacterial osteitis (CNO) in adults.

    Winter EM, Dekkers OM, Andreasen CM, et al.

    Annals of the rheumatic diseases 2024; doi:10.1136/ard-2024-226446.

    PMID: 39608805
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    Anterior chest wall in SAPHO syndrome: magnetic resonance imaging findings.

    Yu M, Cao Y, Li J, et al.

    Arthritis research & therapy 2020; (22(1)):216 doi:10.1186/s13075-020-02309-6.

    PMID: 32928273
  9. 9

    Axial Skeleton Bone Marrow Changes in Inflammatory Rheumatologic Disorders.

    Reijnierse M

    Seminars in musculoskeletal radiology 2023; (27(1)):91-102 doi:10.1055/s-0043-1761496.

    PMID: 36868247
  10. 10

    [SAPHO-Synovitis, acne, pustulosis, hyperosteosis, osteitis].

    Hesse N, Hoppe B, Reidler P, Schmitt R

    Radiologie (Heidelberg, Germany) 2025; (65(9)):681-687 doi:10.1007/s00117-025-01487-1.

    PMID: 40694075
  11. 11

    Multimodal imaging findings of SAPHO syndrome with no skin lesions: A report of three cases and review of the literature.

    Duan N, Chen X, Liu Y, et al.

    Experimental and therapeutic medicine 2016; (12(4)):2665-2670 doi:10.3892/etm.2016.3689.

    PMID: 27698770
  12. 12

    Practical Interpretation of Bone Scintigraphy: Metastases, Fractures, and Beyond.

    Haug LP, Brown PJ, Bishay SE, et al.

    Radiographics : a review publication of the Radiological Society of North America, Inc 2026; (46(2)):e250055 doi:10.1148/rg.250055.

    PMID: 41538361
  13. 13

    SAPHO syndrome with acne fulminans and severe polyosteitis involving axial skeleton.

    Divya BL, Rao PN

    Indian dermatology online journal 2016; (7(5)):414-417 doi:10.4103/2229-5178.190495.

    PMID: 27730042
  14. 14

    A case of synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome with isolated lesions of the thoracic spine.

    Hattori K, Takahashi N, Suzuki M, et al.

    Modern rheumatology case reports 2023; (7(1)):243-246 doi:10.1093/mrcr/rxac030.

    PMID: 35349712
  15. 15

    SAPHO and CRMO: The Value of Imaging.

    Jurik AG, Klicman RF, Simoni P, et al.

    Seminars in musculoskeletal radiology 2018; (22(2)):207-224 doi:10.1055/s-0038-1639469.

    PMID: 29672809
  16. 16

    Imaging features in patients with SAPHO/CRMO: a pictorial review.

    Himuro H, Kurata S, Nagata S, et al.

    Japanese journal of radiology 2020; (38(7)):622-629 doi:10.1007/s11604-020-00953-1.

    PMID: 32356235
  17. 17

    Imaging for Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis (SAPHO) Syndrome.

    Schaub S, Sirkis HM, Kay J

    Rheumatic diseases clinics of North America 2016; (42(4)):695-710 doi:10.1016/j.rdc.2016.07.011.

    PMID: 27742022
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    How nonbacterial osteomyelitis could be discriminated from tuberculosis in the early stages: the simple algorithm.

    Kostik MM, Kopchak OL, Maletin AS, et al.

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    PMID: 32514675

This page explains SAPHO syndrome testing for informational purposes only and does not constitute medical advice. Your clinician should interpret your scans, blood tests, and any biopsy in the context of your symptoms.

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