CAPS, or Cryopyrin-Associated Periodic Syndromes, is a group of rare autoinflammatory diseases caused by a genetic mutation affecting the cryopyrin protein, leading to increased inflammation. CAPS is usually linked to a disease-causing change in the NLRP3 gene, which provides instructions for making cryopyrin. The altered protein can over-activate the body’s inflammatory response, including the interleukin-1 pathway. Most cases are associated with an inherited variant, but some people have a new variant that was not inherited. In a portion of people with CAPS, routine genetic testing does not identify a variant.
It includes three conditions: Neonatal Onset Multisystem Inflammatory Disease (NOMID), Muckle-Wells Syndrome (MWS), and Familial Cold Autoinflammatory Syndrome (FCAS). The three forms: FCAS, MWS and NOMID/CINCA are commonly described as a spectrum rather than entirely separate diseases. Symptoms can overlap, and severity varies. NOMID is also known as chronic infantile neurologic, cutaneous and articular (CINCA) syndrome.
Types of CAPS
CAPS includes three main conditions:
| Condition | Description |
| Neonatal Onset Multisystem Inflammatory Disease (NOMID) | The most severe form, typically presenting in infants with fever, a hive-like rash, and potential neurological issues (CINCA) syndrome. See patient stories here. |
| Muckle-Wells Syndrome (MWS) | Characterized by recurrent episodes of fever, rash, joint pain, and possible hearing loss. Symptoms can last from one to three days. See patient stories here. |
| Familial Cold Autoinflammatory Syndrome (FCAS) | Triggered by cold exposure, causing a hive-like rash, fever, and joint pain. Episodes are usually brief. See patient stories here. |
Symptoms
Common symptoms across the CAPS spectrum include:
- Recurrent fever
- Skin rashes (hive-like or maculopapular)
- Joint pain and swelling
- Red eyes
- Headaches
- Symptoms s vary by person and form. In addition to fever, rash, joint symptoms and eye inflammation, CAPS can involve hearing loss, or other neurologic problems, and—in severe or longstanding disease—amyloidosis affecting organs such as the kidneys. Not everyone experiences all of these.
- FCAS episodes are often triggered by cold and may begin within hours, typically lasting less than a day
- MWS episodes can occur without cold exposure and vary in duration.
- NOMID/CINCA usually begins in infancy and can cause persistent inflammation rather than only brief attacks. These patterns are typical, not rules for every individual.
Diagnosis and Treatment
Diagnosis is based on the whole clinical picture, including symptoms over time, examination, family history and laboratory evidence of inflammation. Genetic testing can help, but a negative result does not always rule out CAPS. Blood tests may include inflammatory markers such as C-reactive protein and serum amyloid A. Skin biopsy and imaging may be used in selected cases, but they are not necessarily routine or required for everyone.
Effective treatments often target interleukin-1, including medications like anakinra, rilonacept, and canakinumab. Early diagnosis and treatment are crucial to prevent long-term damage to organs and improve quality of life.
Recently, as reported on Inside Precision Medicine, researchers at the University of California in San Diego, may have uncovered a key mechanism (CAPS). The study, published in Science Signaling, shows how two specific proteins work together to destroy immune cells and release harmful inflammatory signals throughout the body.
Key Findings from the Research
To understand what triggers this intense inflammation, the research team studied both human blood samples and mouse models:
- Elevated Baseline Inflammation: By analyzing white blood cells (neutrophils) from six CAPS patients, scientists discovered that these immune cells contained unusually high levels of IL-1beta even when patients were not actively experiencing a flare-up.
- Cell Destruction Mechanism: Two pore-forming proteins—gasdermin D and gasdermin E—were found to cluster together on the outer membrane of neutrophils. Their combined activity causes the cell membranes to stiffen, tear, and burst open.
- A Back-Up Role: Gasdermin D is the main driver of this cell rupture. However, the study revealed that gasdermin E can step in and take over the process if gasdermin D is disabled or missing.
- Improved Outcomes in Animal Models: In mouse models, disabling both gasdermin D and gasdermin E reduced overall inflammation and increased survival rates significantly more than disabling gasdermin D alone.
Implications for Future Treatments
Currently, treatments for CAPS focus on blocking IL-1beta signaling after it has already been released. This study suggests a different medical strategy: stopping the cell-bursting mechanism before the inflammatory signals can be released into the body. Because gasdermin E can take over when gasdermin D is blocked, future therapies may need to target both proteins simultaneously to be fully effective. Clinical trials will be necessary to determine whether drugs designed to block both gasdermin proteins are safe and effective for patients.
In the meantime, because ongoing inflammation can lead to lasting complications, including hearing or vision problems, neurologic effects, and amyloidosis, early recognition and effective treatment can help reduce these risks. As these conditions are hard to diagnose, some symptoms over a wide spectrum, and may affect only between one and five in a million, developing clinical trials will be very challenging. The FDA is currently proposing a new framework for trials for these rare and ultra-rare diseases.
