Rare diseases

CAPS diagnoses delayed by decades in Australia

Diagnosis of cryopyrin-associated periodic syndromes (CAPS) is frequently delayed in Australia despite almost all patients having a family member affected with similar symptoms, a team of Australian rheumatologists report.

In the first population-based study of CAPS in Australia, the researchers found the average delay in diagnoses was  20.6 years for milder syndromes including familial cold auto-inflammatory syndrome (FCAS) and Muckle–Wells syndrome (MWS).

The average diagnostic delay for the more severe neonatal onset multi-inflammatory disorder (NOMID) – also known as chronic infantile neurological cutaneous and articular (CINCA) syndrome – was 2.1 years.

Coauthor of the study Dr Navid Adib from Queensland Paediatric Rheumatology Services told the limbic early referral from GPs and general paediatricians and better access to genetic testing were important factors for earlier diagnosis.

“These are very rare conditions but once you have had a patient with CAPS, it is hard to forget that constellation of symptoms including rashes, periodic fever and arthralgia,” he said.

The survey of specialists and clinicians reporting to the Australian Paediatric Surveillance Unit identified just 18 cases. Five patients with MWS were from the same family. Rheumatologists were most likely to report cases, ahead of allergists/immunologists.

“It is very difficult to capture all cases definitively and the estimated prevalence of 1 in a million is likely to be an underestimate,” Dr Adib said.

“In the US, the estimate ranges from 1 in 300,000 to 1 in a million which could reflect their genetic makeup or the fact they are ahead of us in identifying these patients and doing the genetic confirmations.”

He said periodic fever and rash and exaggerated immune responses to immunisations were red flags for CAPS in infants.

He added that once a diagnosis was confirmed, daily injections of anakinra could almost completely normalise inflammation. However a longer-acting interleukin-1 therapy such as canakinumab would provide some relief from daily injections especially for children.

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