SAPHO syndrome

Nobody yet knows exactly what causes SAPHO syndrome. Doctors regard it as a disorder of inflammation, in which the immune system itself inflames bone, joint and skin; it is not thought to be an infection or a cancer, though scans can sometimes make it look like either. The name is simply a list of the five features that make it up.

It is often placed in the same family as spondyloarthritis and psoriatic arthritis, though not every expert agrees it belongs there: it lacks the tie to the HLA-B27 gene those conditions often have, and inflammation inside the bone is not typical of them. Several of its features are those of axial spondyloarthritis, inflammation where tendons and ligaments anchor to bone, called enthesitis, among them. Inflammatory bowel disease is linked with it, and for some the joint symptoms resemble those of enteropathic arthritis. It is more common in women. Why one person develops it and another does not remains unclear.

Most typical of all is a painful swelling over the front of the chest, at the sternoclavicular joints where each collarbone meets the breastbone, and along the breastbone's centre. The area can turn tender and swollen, and it can grow firm to the touch as the bone thickens. Plain costochondritis is a far commoner cause of pain here, but the swelling and thickened bone of SAPHO mark it out.

You may also notice:

• A stiff, painful back, pelvis or sacroiliac joints (the joints linking the pelvis to the lowest part of the spine)
• Bones of the arms or legs that ache or become inflamed
• Swelling in joints of the limbs, a knee or an ankle for example
• Palmoplantar pustulosis, in which the palms and soles break out in small blisters full of pus
• Acne that is severe or will not clear, sometimes worse than ordinary acne

The skin problems and the bone problems may start years apart, and there is no fixed order. Pustulosis or severe acne can precede the bone pain by a long time, or follow it. That is why the link between them is easily missed.

Several findings, never one result, make the diagnosis of SAPHO. It depends on seeing the whole picture: chest-wall inflammation of the typical kind, any trouble in the spine, the pelvis or the long bones, and skin problems now or in the past. Your story and an examination bring these strands together, and that matters greatly when the features may have appeared years apart.

Imaging is central. An MRI scan can reveal inflammation in the bone and the tissue around it, and a bone scan can light up the chest wall in the pattern that suggests SAPHO. Blood tests may point to inflammation, yet in many people they are normal, which is why a normal result cannot rule SAPHO out.

Excluding other causes that a scan can make look the same, a bone infection first of all and, now and then, a tumour, is a central part of the assessment. That is why SAPHO is often the diagnosis left once the others are ruled out, and why a biopsy, a small piece of bone taken for testing, is occasionally needed to exclude infection and cancer for certain. Where a joint can be reached, such as a sternoclavicular joint or a swollen joint in a limb, ultrasound can help to show whether inflammation is active. Point-of-care ultrasound is part of the consultation with Dr Borukhson, so a scan of such a joint often fits into the first consultation. The ultrasound clinic page sets out what the scan entails.

When SAPHO has been recognised, good treatment is usually possible, shaped around the features that affect you most. Treatment generally opens with anti-inflammatory tablets (NSAIDs), which for many people keep symptoms well in check. They are used with care, at the lowest dose that helps, watching for effects on the stomach, kidneys and blood pressure.

Where bone pain stands out, or NSAIDs are not enough, bisphosphonates, medicines that act on bone, often bring worthwhile relief. For disease that persists or causes more trouble, a disease-modifying medicine such as methotrexate can help to calm the inflammation, and biological medicines can help where other treatment has not worked, in particular the anti-TNF medicines familiar from the wider spondyloarthritis group. The evidence for them in SAPHO rests mainly on reports of small groups of patients and on specialists' experience, with no large trials, and adalimumab is not routinely funded by NHS England for chronic non-bacterial inflammation of bone, so each is weighed case by case. Which medicine suits depends on the features that dominate and on how the condition is behaving. Methotrexate slows the immune system down, which can make infections more likely.

The skin is involved so often that a dermatologist commonly shares the care, treating the pustulosis or acne while the bones and joints are treated too. The aims do not change: less pain, less inflammation and joints and bones that keep working for years to come, with the plan revisited from time to time.

Alongside the treatment, a few everyday habits make SAPHO easier to live with.

• Keep moving, gently. Stretching and regular activity help the chest wall, back and joints to stay flexible, in quieter spells too.
• Ride out flares. SAPHO tends to wax and wane: during a flare do less, then build up again as it eases, without forcing the pace.
• Look after your skin. Keep to the skin-care plan your dermatology team agreed, and mention any rash that is new or getting worse, so it is treated in good time; a rash that spreads across the body, or skin that blisters or peels beyond the pustulosis of your palms and soles, is a 999 or A&E emergency, as the first list under When to seek help says.
• Think about stopping smoking. Most people with pustulosis on the palms and soles smoke or have smoked, and smoking makes it worse, so stopping can help the skin as well as your general health. Your GP can help you stop.
• Keep your review appointments. They let the treatment be adjusted and any new feature be noticed in good time.

Once the diagnosis is settled and the plan fits, many find the condition behaves more predictably and is simpler to manage.

SAPHO can look like a bone infection, and chest pain always deserves care, so some symptoms need checking in their own right rather than being put down to the condition. The two lists below hold them, the most serious first, and anything else is covered after them.

Treat any of these as a 999 or A&E emergency: call 999 and do not drive yourself to A&E.

• Severe illness with suspected sepsis: a high fever with shaking, confusion, rapid breathing, or feeling dramatically worse over hours
• With a fever or feeling unwell, a rash that does not fade when you press it, a stiff neck with eyes that cannot bear bright light, or skin, lips or tongue turning blue, grey, pale or blotchy, since these can be signs of meningitis or sepsis, as can a very bad headache, confusion or a first seizure with a fever or feeling unwell; on black or brown skin the rash and the change of colour may be easier to see on the palms of the hands or the soles of the feet
• Chest pain that is crushing, tight or like a pressure, that spreads to an arm, the jaw, the neck, the stomach or the back, that comes with breathlessness, sweating, feeling sick or feeling light-headed, or that came on suddenly and does not go away
• A rash that spreads across the body, skin that blisters or peels, or lips, mouth or eyes that turn sore or swollen, since this can be a severe reaction to a medicine, such as Stevens-Johnson syndrome, which needs treating in hospital straight away, though the pustulosis of your palms and soles, the small pus-filled blisters that SAPHO itself brings, is not what is meant
• Numbness or tingling around the back passage, genitals or inner thighs, new difficulty passing urine or controlling your bladder or bowels, a change in feeling during sex, or pain, tingling, weakness or numbness in both legs, since these can mean pressure on the nerves at the base of the spine, which needs emergency treatment
• Vomiting blood, or bleeding from the back passage that is heavy or will not stop, most of all with faintness, confusion or pain in the abdomen, or vomit that is black or dark brown, since anti-inflammatory tablets, the usual first treatment for SAPHO, can make the stomach bleed
• Lips, mouth, throat or tongue that suddenly swell, a throat that feels tight, very fast breathing or a struggle to breathe or to swallow, skin, tongue or lips turning blue, grey or pale (on black or brown skin this may be easier to see on the palms of the hands or the soles of the feet), becoming suddenly very confused, drowsy or dizzy, or fainting and not being able to be woken, since this can be a severe allergic reaction, anaphylaxis, which can follow a dose of any medicine

Any of these needs an assessment that is urgent, on the same day, from your GP, your rheumatology team or NHS 111:

• A fever, or feeling generally unwell, on immunosuppressant, biologic or steroid treatment, since an infection has to be treated early
• A bony area that becomes red and hot and keeps getting more painful, or bone or joint pain that comes with a fever or with feeling ill in yourself, since an infection of the bone or the joint has to be ruled out, and SAPHO can resemble one; for a hot, swollen joint with a fever, the hot-joint lines below give A&E or NHS 111, and for one that takes no weight at all, or cannot be moved, 999 or A&E
• A joint that is hot and swollen, with a fever or feeling unwell, since an infected joint has to be ruled out at once, at A&E or through NHS 111
• A joint that has become hot and very swollen suddenly, or is worsening quickly, even without a fever, since an infected joint does not always announce itself with one; a joint that will take no weight at all, or that cannot be moved, is a 999 or A&E emergency, whether or not there is a fever
• Chest pain you have not felt before, or that differs from your usual chest-wall ache, with none of the features in the first list, since a cause other than SAPHO has to be ruled out that day; chest pain that comes with back pain you have not had before, or unlike your usual back pain, is a 999 or A&E emergency, as the paragraph below says
• Black or dark red stools, on anti-inflammatory tablets, since a bleed in the stomach or gut has to be found that day
• Being near someone with measles, chickenpox or shingles, while you take a medicine that weakens the immune system, since measles and chickenpox can be dangerous when the immune system is weakened, and you can catch chickenpox from someone with shingles if you have never had chickenpox; NHS 111 can tell you what to do that day

Chest pain that arrives together with back pain you have not had before, or that feels different from your usual back pain, is a 999 or A&E emergency. Call 999 and do not drive yourself to A&E. Short of the signs in the lists above, a flare that is not easing on your treatment goes to your rheumatology team or GP within days, and if SAPHO has not been diagnosed and you have pain and swelling over the front of the chest, or bone pain alongside a skin problem such as pustulosis or severe acne, an assessment within days, through your GP or booked directly, is worthwhile. Where the spine is involved, the axial spondyloarthritis guide's seek-help section lists the back's other warning signs. Anything long established and unchanging can be raised at your next routine review with your rheumatology team. If you take methotrexate, another DMARD or a biologic, the warning signs that belong to each are set out in our guides to methotrexate, DMARDs and biologics and JAK inhibitors. If you cannot tell how urgent something is, asking is never a mistake.

Many people with SAPHO are first given another diagnosis, because the skin and the bones may be affected years apart and because inflamed, thickened bone on a scan can pass for an infection or a tumour. The result can be real anxiety, and at times investigations that could have been spared. When a specialist identifies the pattern, links the skin to the bones and rules out the alternatives with care, the uncertainty can lift. SAPHO responds to treatment once it is named, so a correct diagnosis leads to proper care of skin and bone alike.

What do the letters in SAPHO mean?

Each letter names a feature: synovitis (an inflamed joint lining), acne, pustulosis (a rash of pus spots, usually on the palms and soles), hyperostosis (bone that thickens and overgrows) and osteitis (inflammation inside the bone). Some people have only a few of the five, and those they have can come at different times. It is really one inflammatory condition that ties typical bone and joint problems to typical skin problems, most often around the front of the chest.

Why does SAPHO syndrome so often go unrecognised?

Being rare, it may not come to mind, and when the skin and the bone problems arrive years apart, nobody may connect them. Scans add to the confusion, since thickened and inflamed bone can look like an infection on them, or even a tumour, which sometimes brings worry, and tests nobody needed, before the real pattern is spotted. Putting every piece together, skin problems past and present included, is what makes the diagnosis possible.

Which tests point to SAPHO syndrome?

The diagnosis never rests on one test alone. A specialist pieces it together from the pattern, with chest-wall inflammation the leading sign, and from scans: MRI, and in some cases a bone scan, whose telltale uptake over the front of the chest can point to it. Excluding other causes, infection in particular and occasionally a bone tumour, is a central part of the work, so SAPHO is often the diagnosis left once these are excluded. To settle any doubt about infection or cancer, a sliver of bone is now and then sent for testing (a biopsy).

What treatment helps SAPHO syndrome?

What you are offered depends on how SAPHO is affecting you. Most people begin with anti-inflammatory tablets (NSAIDs), which are enough for many. Bisphosphonates, medicines that work on bone, often ease bone pain where NSAIDs fall short. For disease that persists or troubles you more, a disease-modifying medicine such as methotrexate, or a biological medicine such as an anti-TNF, can help where other treatment has failed. A dermatologist often looks after the skin alongside, so that skin and bone are treated together.

Which signs with SAPHO syndrome need urgent help?

Chest pain with any of the features in the first list under When to seek help; chest pain that comes with back pain you have not had before, or unlike your usual back pain; numbness around the back passage or genitals, new trouble controlling the bladder or bowels, or weakness or numbness in both legs; a joint that will take no weight at all or cannot be moved: each is a 999 or A&E emergency, and so is anything else in that list. Call 999 and do not drive yourself to A&E. Short of those signs, a bony area that becomes red and hot and keeps getting more painful, or bone or joint pain that comes with a fever or with feeling ill in yourself, needs an assessment the same day, from your GP, your rheumatology team or NHS 111, because an infection has to be ruled out; chest pain you have not felt before, or that differs from your usual chest-wall ache, goes to your GP, your rheumatology team or NHS 111 the same day too; for a hot, swollen joint with a fever, the second list gives A&E or NHS 111, and the rest of that list gives the other signs that need the same day.