OBJECTIVES: CAPS is a spectrum of rare inherited autoinflammatory syndromes. It is an ultra-orphan disease affecting approximately 70 patients in the UK. CAPS patients are at increased risk of developing AA amyloidosis (AA) and subsequent end-stage renal failure (ESRF). This study aimed to model the impact of a new treatment, canakinumab, on the progression of AA in patients with CAPS. METHODS: A Markov model was developed which comprised four health states: CAPS, CAPS with AA, CAPS with ESRF and dead. Based on the literature, 25% of CAPS patients are thought to develop AA over their lifetime. The risks of ESRF and death in patients with AA were obtained from published observational studies and life expectancy in CAPS patients with ESRF was based on expert opinion. Excess mortality in CAPS for reasons other than AA was estimated from rheumatoid arthritis, another systemic inflammatory disease. Treatment efficacy for canakinumab was obtained from the results of a pivotal clinical trial. The model was run for a typical adult patient and a typical paediatric patient and assumed that AA was not present at treatment initiation. RESULTS: Assuming a UK CAPS population of 70 patients, if canakinumab was initiated at the age of 4 years, a total of 18 AA and 8 ESRF cases would be avoided, and patients would gain 13.7 years of life on average compared to those not treated with canakinumab. Assuming treatment initiation at the age of 38 years (estimated mean age at diagnosis), a total of 11 AA and 4 ESRF cases would be avoided and patients would gain 10.3 years of life on average. CONCLUSIONS: Based on a model estimating the progression of AA in CAPS, treatment with canakinumab is associated with a gain of 10 to 14 life years due to a reduced incidence of AA and ESRF.