SAPHO syndrome

The exact cause of SAPHO syndrome is not known. It is understood as an inflammatory condition in which the body's immune system drives inflammation in the bones, the joints and the skin, rather than as an infection or a cancer, even though it can sometimes resemble those on scans. The name gathers together its main features: synovitis, acne, pustulosis, hyperostosis and osteitis.

SAPHO is generally considered to sit within the same broad family as the spondyloarthritis and psoriatic arthritis group of conditions. It shares features with axial spondyloarthritis, including a tendency to inflammation where tendons and ligaments attach to bone, known as enthesitis. There are also recognised links with inflammatory bowel disease, and in some people the joint problems overlap with those seen in enteropathic arthritis. Why one person develops SAPHO and another does not is not yet understood.

The most characteristic feature of SAPHO is pain and swelling at the front of the chest, where the collarbone meets the breastbone (the sternoclavicular region) and along the midline of the breastbone. This area can become tender, swollen and noticeably firm as the bone thickens. Simple costochondritis is a far more common cause of pain in this area, but the swelling and bone thickening of SAPHO set it apart.

Other features may include:

• Pain and stiffness in the spine, pelvis or the joints between the pelvis and the base of the spine
• Aching or inflammation in the long bones of the arms and legs
• Swelling of peripheral joints, such as the knees or ankles
• Palmoplantar pustulosis, a rash of small pus-filled blisters on the palms of the hands and the soles of the feet
• Severe or persistent acne, sometimes more troublesome than ordinary acne

An important point is that the skin and bone problems can appear years apart, and either one may come first. Someone may have had pustulosis or severe acne long before the bone pain begins, or the reverse. Because of this, the connection between the two is easily missed.

There is no single test that confirms SAPHO. The diagnosis is made by recognising the overall pattern: the characteristic inflammation at the front of the chest, any involvement of the spine, pelvis or long bones, and the associated skin problems, past or present. A careful history and examination bring these threads together, which matters greatly in a condition whose features are often spread out over time.

Imaging plays a central role. MRI can show inflammation within the bone and the surrounding tissues, and a bone scan sometimes reveals the typical pattern of uptake in the chest wall that points towards SAPHO. Blood tests may show signs of inflammation but are often unremarkable, so normal results do not exclude the condition.

A key part of the assessment is ruling out other explanations, particularly a bone infection or, occasionally, a tumour, both of which can look similar on scans. For this reason SAPHO is frequently reached as a diagnosis of exclusion, and now and then a small sample of bone (a biopsy) is needed to be certain there is no infection or cancer. Where a joint such as the sternoclavicular joint or a swollen peripheral joint is accessible, point-of-care ultrasound during the consultation can help show whether active inflammation is present. Dr Borukhson uses ultrasound in the clinic, and you can read more on the ultrasound clinic page.

Once SAPHO is recognised, it can usually be treated effectively, with the plan tailored to how the condition affects you. Anti-inflammatory tablets (NSAIDs) are generally the first step and control symptoms well in many people. They are used thoughtfully, at the lowest helpful dose, with attention to any effect on the stomach, kidneys or blood pressure.

When bone pain is prominent or NSAIDs are not enough, medicines called bisphosphonates, which act on bone, often provide useful relief. For persistent or more troublesome disease, conventional disease-modifying medicines such as methotrexate can help settle the inflammation, and biologic medicines, particularly the anti-TNF treatments used across the spondyloarthritis family, can be very effective. The choice depends on which features dominate and how the condition is behaving.

Because the skin is so often involved, care is frequently shared with a dermatologist so that the pustulosis or acne is managed alongside the bone and joint problems. The aim throughout is to ease pain, calm inflammation and protect long-term function, with the plan reviewed and adjusted over time.

Living well with SAPHO is helped by steady, practical habits alongside your treatment.

• Keep gently active. Regular movement and stretching help maintain flexibility in the chest wall, spine and joints, even during quieter spells.
• Pace flares. Symptoms tend to come and go, so ease back during a flare and build activity up again as it settles, rather than pushing through.
• Look after your skin. Follow the skin-care plan agreed with your dermatology team, and raise any new or worsening rash so it can be treated promptly.
• Consider stopping smoking. Pustulosis of the palms and soles is strongly linked with smoking, and stopping can benefit both the skin and your general health. Support to stop is available through your GP.
• Attend your reviews. Regular follow-up allows treatment to be fine-tuned and any new features to be picked up early.

Many people find that, once the diagnosis is clear and a suitable plan is in place, symptoms become more predictable and easier to manage.

Because SAPHO can resemble a bone infection, and because chest pain always deserves care, certain symptoms should prompt assessment in their own right rather than being assumed to be part of the condition.

Arrange a prompt, same-day medical review if you develop:

• A bony area that becomes hot, red and increasingly painful, especially with a fever or feeling generally unwell, as a bone infection needs to be excluded
• A rapidly worsening swollen, hot joint

Call 999 or go to A&E immediately for:

• Sudden severe chest pain with breathlessness, sweating or a feeling of pressure, which always needs the heart ruled out first
• New back pain with leg weakness, numbness, or difficulty controlling the bladder or bowels

Stable, long-standing symptoms can be reviewed routinely. When something feels different or you are unsure, it is always safer to be checked.

SAPHO syndrome is rare and frequently misdiagnosed, partly because its skin and bone features can appear years apart, and partly because the inflamed, thickened bone can mimic infection or a tumour on scans. This can lead to considerable worry and, sometimes, to investigations that turn out not to be needed. A specialist assessment that recognises the pattern, brings the skin and bone problems together and carefully excludes other causes can bring clarity and reassurance. Importantly, once SAPHO is recognised it is treatable, so reaching the right diagnosis opens the way to effective care for both the bones and the skin.

What does SAPHO stand for?

SAPHO is an acronym for the condition's main features: synovitis (inflammation of the joint lining), acne, pustulosis (a pustular skin rash, usually on the palms and soles), hyperostosis (thickening and overgrowth of bone) and osteitis (inflammation within the bone itself). Not everyone has all of these features, and they need not appear together. SAPHO is best thought of as a single inflammatory condition that links characteristic bone and joint problems with characteristic skin problems, most often centred on the front of the chest.

Why is SAPHO syndrome so often missed or misdiagnosed?

SAPHO is rare, so it is not always considered, and its features can be spread out over time. The skin and bone problems may appear years apart, so the link between them is easy to overlook. On scans, the inflamed, thickened bone can resemble a bone infection or even a tumour, which sometimes leads to unnecessary worry and investigation before the true pattern is recognised. Bringing the whole picture together, including any past or present skin problems, is what allows the diagnosis to be made.

How is SAPHO syndrome diagnosed?

There is no single test for SAPHO. The diagnosis rests on recognising the characteristic pattern, particularly inflammation at the front of the chest, together with imaging such as MRI and sometimes a bone scan, which can show the typical uptake in the chest wall. An important part of the assessment is excluding other explanations, especially infection and, occasionally, a bone tumour, so SAPHO is often reached as a diagnosis of exclusion. Now and then a small sample of bone (a biopsy) is needed to be certain there is no infection or cancer.

How is SAPHO syndrome treated?

Treatment is tailored to how the condition affects you. Anti-inflammatory tablets (NSAIDs) are usually the first step and help many people. Medicines called bisphosphonates, which act on bone, often ease bone pain when NSAIDs are not enough. For persistent or more troublesome disease, conventional disease-modifying drugs such as methotrexate, or biologic medicines such as anti-TNF treatments, can be very effective. The skin problems are frequently managed together with a dermatologist, so that both the bones and the skin are addressed.

When should I seek urgent help with SAPHO syndrome?

Seek prompt, same-day medical review if a bony area becomes hot, red and increasingly painful, especially with a fever or feeling generally unwell, because a bone infection needs to be excluded urgently. Sudden severe chest pain with breathlessness, sweating or a feeling of pressure should be treated as an emergency and assessed straight away, as chest pain always needs the heart ruled out first. New back pain with leg weakness, numbness or difficulty controlling the bladder or bowels needs emergency assessment. When in doubt, it is always safer to be checked.