CAP syndromes are autoinflammatory diseases that are usually inherited and include three different conditions with overlapping syndromes of increasing severity:
CAP syndromes are extremely rare, affecting about one person in every one million people. For example, in England, approximately 50 patients have been diagnosed with CAPS through the National Amyloidosis Centre (NAC). It is believed that there may be another ~20 further cases as yet undiagnosed, since the condition is diagnosed late or not at all in many cases, and a child is born with CAPS about once every 2 years in England.
The severity and frequency of symptoms is different for each of the three conditions. FCAS is considered the milder form, while NOMID is the most severe.
Common symptoms of CAPS are recurrent rash (urticaria or hives), fatigue, fever, joint pain and conjunctivitis. Symptoms may be triggered by cold temperature, stress and exertion. Additionally, the more severe CAP syndromes have other characteristic symptoms (see above diagram).
In CAPS, activation of an inflammatory response occurs as a result of a change in a gene in the cells of the innate immune system, rather than due to invading germs. The gene (known under various names as: NLRP3, NALP3, cryopyrin or CIAS1) directs the formation of a messenger substance called interleukin -1 beta (IL-1β), which promotes the inflammatory response. In CAPS, a change in this gene can lead to a continuous overproduction of IL-1β, and, therefore, to an inflammatory response that affects the entire body.
1. Shinkai K, McCalmont TH, Leslie KS. Clin Exp Dermatol 2007; 33(1): 19.
2. www.ucl.ac.uk/drupal/site_amyloidosis/sites/amyloidosis/files/caps.pdf. Accessed January 13, 2017.
3. Farasat S et al. Arch Dermatol 2008;144(3):392–402.
4. Touitou et al. Best Pract Res Clin Rheumatol 2008;22(5):811–29.