What is CAPS?
Cryopyrin-Associated Periodic Syndromes (CAPS) are a group of rare inherited inflammatory conditions caused by variants in the NLRP3 gene. There are three types mild, moderate and severe.
These have previously been named:
- FCAS – Familial Cold Autoinflammatory Syndrome (mild)
- MWS – Muckle-Wells Syndrome (moderate)
- NOMID/CINCA – Neonatal-Onset Multisystem Inflammatory Disease / Chronic Infantile Neurological Cutaneous and Articular Syndrome (severe)
These syndromes affect the immune system and cause repeated inflammation throughout the body.
They exist on a spectrum.
MILD - FCAS
MODERATE - MSW
SEVERE - NOMID/CINCA
Who does CAPS affect?
CAPS is very rare. It affects males and females equally. Many cases may go undiagnosed.
CAPS does not discriminate, anyone can be affected. As most cases are inherited, family history is important.
People with CAPS often present with symptoms that can look like other diseases. Because symptoms are often non-specific and periodic, meaning that they come and go, diagnostic delays as misdiagnoses are common. *In 2016, the estimated prevalence of CAPS in Australia was 1 in 1 million people in Australia, but the actual number is likely to be more than 5x higher.
What Causes CAPS?
CAPS is caused by changes (variants) in the NLRP3 gene, which controls a protein called cryopyrin. This protein helps regulate inflammation. When the gene doesn't work properly, it leads to too much inflammation.
- One abnormal copy of the gene, inherited from one parent is enough to cause the condition (autosomal dominant pattern).
- About 75% of people with mild or moderate CAPS inherit it from a parent.
- Severe CAPS often results from a new (de novo) mutation before birth.
The gene is active in white blood cells and cartilage cells, which explains symptoms like joint swelling, bone growth changes, and pain.
Common Symptoms
- Non-itchy skin rash (urticaria-like)
- Joint and muscle pain
- Eye inflammation (red and painful eyes)
- Hearing problems (hearing loss)
- Headaches and other neurological issues
- Ongoing (chronic) inflammation between flare ups
- Fever and chills
Symptoms can vary widely between people and between CAPS types
1. Mild (previously FCAS)
- Flare-ups are triggered by cold temperatures, sudden temperature changes, swimming, or air conditioning
- Symptoms may include:
- Rash
- Fever
- Red eyes
- Headaches
- Nausea and joint pain
- Episodes usually last less than 24 hours
- Some people may have digestive symptoms, such as nausea, diarrhoea, or stomach pain
Tip: See a gastroenterologist if you have ongoing digestive symptoms.
2. Moderate (previously MWS)
- Flares may happen randomly or after cold exposure
- Episodes usually last 1 to 5 days
- Common symptoms:
- Rash
- Joint pain
- Red eyes
- Headaches
- May lead to progressive hearing loss during teenage years
- If untreated, there is a risk of kidney damage (amyloidosis)
- Eye inflammation, swollen lymph nodes, and liver or spleen enlargement may also occur
3. Severe (previously NOMID / CINCA)
- Begins in early infancy or at birth
- Symptoms may include:
- Constant inflammation: rash, fever, organ involvement
- Neurological problems: meningitis (inflammation around the brain)
- high pressure in the brain, hearing or vision loss, developmental delay, seizures
- Bone changes: joint swelling, overgrowth, short stature, bone deformities
- Eye symptoms: blurred vision, eye pain, redness, scarring, retinal damage and risk of blindness
Important: See a specialist eye doctor for regular monitoring.
Early diagnosis and treatment can improve outcomes and reduce complications.
How is CAPS Diagnosed?
Doctors may suspect CAPS based on:
- Medical history and physical symptoms
- Family history
- Blood tests (done during and between flare-ups)
- Genetic testing for NLRP3 mutations
Other possible tests:
- Eye and hearing exams
- MRI scans
- Lumbar puncture (to check spinal fluid)
- Skin biopsy
CAPS Diagnostic Criteria
Diagnosis usually includes:
- High inflammation markers (CRP or SAA)
- At least two of these typical symptoms:
- Hive-like rash
- Cold-triggered episodes
- Hearing loss
- Joint or muscle pain
- Meningitis
- Bone or skeletal changes
Why Early Diagnosis Matters
Getting diagnosed and starting treatment early:
- Helps prevent serious complications
- Reduces damage to organs like kidneys, eyes, and ears
- Improves long-term health and quality of life
Blood Test and Monitoring
Doctors may use blood tests to monitor the disease and response to treatment.
Common findings include:
- High C-reactive protein (CRP) and serum amyloid A (SAA)
- High white blood cell count (especially neutrophils)
- Mild anaemia
Spinal fluid testing - High white cells in spinal fluid (in severe cases)
CAPS is treated with medications that block interleukin-1 (IL-1), a protein that drives inflammation. These medicines help reduce flare-ups and prevent long-term damage.
- Anakinra
- Canakinumab (Available in Australia but not on the PBS/not currently available in New Zealand)
These are injected under the skin. Some people may need higher doses to manage severe symptoms.
NSAIDs (Non-steroidal Anti-inflammatory Drugs): These help reduce pain, inflammation, and fever. Examples include Ibuprofen, Naproxen and Aspirin.
Other helpful treatments:
Physiotherapy and occupational therapy may help you cope with the physical effects of CAPS and improve mobility.
Some individuals may need physical therapy, splints to treat joint alignment, or surgery to correct joint deformities.
IMPORTANT NOTE:
Currently, not all medications commonly used to treat SAIDs are available in Australia and New Zealand, and those available may be difficult to access.
ANZFAID is committed to continuing to advocate for improved options, and timely and affordable access to treatment.
If you love any of the articles on our site we would you love you to share them to help raise awareness.
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