Mostly Dutch and French. Not to be confused with Hyper IgE syndrome or Hyper IgM syndrome. Big database in Nijmegen. A genetic syndrome (autosomal recessive, explained by MVK (mevalonate kinase) gene mutations on chromosome 12p – see Omim) with recurrent febrile attacks starting under 1yr of age.

Attacks last 3-7 days, so may or may not be shorter than TRAPS, occur every 4-8 weeks. Features are:

• Abdo pain, vomiting and diarrhoea (cf constipation of TRAPS)
• Headache, arthralgia
• Swollen cervical lymph nodes – v common, cf TRAPS
• Splenomegaly
• Non-destructive arthritis

Diagnosis is by finding of high IgD (>100U/ml); most also have high IgA (with or without raised IgG and IgM), which is an important clue.

Increased Mevalonic acid in urine during fever.

Febrile attacks in response to immunizations often reported, so may be another clue.

Attacks tend to diminish with age without completely disappearing; amyloidosis seems to occur only rarely (cf TRAPS). Simvastatin is supposed to help!