Muckle-Wells syndrome

Muckle-Wells syndrome (MWS) is a rare hereditary autoinflammatory disorder belonging to the group of cryopyrin-associated periodic syndromes (CAPS), which also includes familial cold autoinflammatory syndrome (FCAS) and neonatal-onset multisystem inflammatory disease (NOMID/CINCA). MWS is caused by gain-of-function mutations in the NLRP3 gene (also known as CIAS1), which encodes the protein cryopyrin (NALP3). These mutations lead to excessive activation of the NLRP3 inflammasome, resulting in overproduction of interleukin-1β (IL-1β), a potent pro-inflammatory cytokine that drives the clinical manifestations of the disease. MWS is characterized by recurrent episodes of fever, urticaria-like skin rash, joint pain (arthralgia) and inflammation (arthritis), conjunctivitis, and fatigue. A hallmark feature that distinguishes MWS from milder CAPS phenotypes is progressive sensorineural hearing loss, which typically develops during childhood or adolescence and can become severe if untreated. Episodes may be triggered by cold exposure, stress, or exercise, but often occur without identifiable triggers. Between flares, patients frequently experience chronic low-grade inflammation with elevated acute-phase reactants such as serum amyloid A (SAA) and C-reactive protein (CRP). The most serious long-term complication of MWS is AA amyloidosis, which results from chronic elevation of SAA and can lead to progressive renal impairment and kidney failure if left untreated. Approximately 25% of untreated patients develop systemic amyloidosis. Treatment has been revolutionized by the availability of IL-1 inhibitors, including anakinra (a recombinant IL-1 receptor antagonist), canakinumab (a monoclonal antibody targeting IL-1β), and rilonacept (an IL-1 trap). These biologic therapies effectively control inflammatory symptoms, normalize inflammatory markers, prevent amyloidosis progression, and may stabilize or partially improve hearing loss when initiated early. Lifelong treatment is generally required, as symptoms recur upon discontinuation of therapy.

Common questions about Muckle-Wells syndrome