Inheritance: autosomal dominant (a parent and some siblings affected)
Molecular defect: short arm of chromosome 12 (12p)
Groups affected: Irish, Scots, other ethnic groups
Age of onset: < 20 years
Duration of an attack: from 1 day to > 2 weeks
Clinical features:
(1) recurrent fever (may be the only symptom)
(2) abdominal pain with diarrhea or constipation, nausea and vomiting
(3) localized myalgias that may migrate
(4) erythematous macules or plaques
(5) periorbital edema and conjunctivitis
(6) arthralgias without arthritis
(7) headache
(8) testicular pain in males
(9) good clinical response to corticosteroids and etanercept
(10) development of amyloidosis with organ failures
Key clinical features for diagnosis:
(1) familial history
(2) prolonged attack
(3) conjunctivitis
(4) localized myalgias
(5) response to steroids
Laboratory findings:
(1) neutrophilia
(2) elevated C-reactive protein
(3) polyclonal gammopathy
(4) low serum type 1 TNF receptor (< 1 ng/mL)
