Muckle-Wells Syndrome in the Setting of Basal Cell Nevus Syndrome

Comment

Classification and Clinical Presentation
The hereditary periodic fever syndromes include the autoinflammatory syndromes and the CAPSs. The autoinflammatory syndromes include familial Mediterranean fever, hyperimmunoglobulinemia D with periodic fever syndrome, and tumor necrosis factor receptor–associated periodic syndrome. The CAPSs are similar but distinct and include familial cold autoinflammatory syndrome, neonatal-onset multisystem inflammatory disease (also known as chronic infantile neurologic cutaneous and articular syndrome, or cutaneous articular syndrome) and MWS.^1,2

Cryopyrin-associated periodic syndromes are rare inherited diseases that result from mutations in the NLRP3 gene. There is a gain-of-function mutation on the NLRP3 gene located on the long arm of chromosome 1 at position 44, which codes for cryopyrin. An NLRP3 gene mutation causes cryopyrin to become hyperactive, leading to the formation of an inflammasome, which is a group of cryopyrin molecules. Inflammasomes, along with other proteins, activate caspase 1 to produce excess IL-1β, leading to persistent inflammatory symptoms.³ IL-1β is one of the key mediators of the body’s response to microbial invasion, inflammation, immunologic reactions, and tissue injury. It affects a large range of cells and organs. Although IL-1β production is critical for the control of pathogenic infections, excessive cytokine production is harmful to the host and can even be fatal.^3,4

Cryopyrin-associated periodic syndromes encompass a disease continuum. The 3 distinct entities share many overlapping features as well as unique and distinguishing characteristics. Familial cold autoinflammatory syndrome is the mildest phenotype and is inherited in an autosomal-dominant fashion. It is characterized by a chronic urticarial eruption that starts early in infancy or childhood. The distribution of the cutaneous eruption is widespread and favors the arms and legs over the face and trunk. A low-grade fever often is seen along with musculoskeletal concerns of arthralgia and pain. Other commonly reported symptoms include conjunctivitis, myalgia, fatigue, and headache. Neurologic symptoms can include headaches. Symptoms usually begin 1 to 2 hours after cold exposure and last less than 24 hours.^5-8

Neonatal-onset multisystem inflammatory disease is the most severe phenotype and occurs sporadically. Continuous symptoms and flares are characteristic and the length of the flare can vary from minutes to days. The cutaneous eruption favors the face, trunk, arms, and legs, and varies in intensity, beginning in infancy or childhood. Fever may be intermittent, mild, or absent. Rheumatologic manifestations include arthralgia and swelling, with approximately one-third of patients experiencing severe disabling arthropathy that causes gross joint deformity. Ocular findings include conjunctivitis, uveitis, papilledema, and even blindness. Neurologic sequelae include headaches, sensorineural hearing loss, and aseptic meningitis. Amyloidosis has been seen as a late complication.^5,8

Muckle-Wells syndrome is a rare hereditary inflammatory disorder. It has no ethnic predisposition and is mostly inherited in an autosomal-dominant fashion. Classically, the condition is characterized by recurrent urticaria beginning at birth with intermittent episodic fever and malaise. The eruption has a predilection for the face, trunk, arms, and legs, which is similar to neonatal-onset multisystem inflammatory disease. Associated myalgia and arthralgia are common as well as ocular findings of conjunctivitis and episcleritis. Neurologic manifestations include headache and progressive sensorineural hearing loss in 60% to 70% of patients.⁶ Abdominal pain may be seen along with rare serositis in MWS but is rare in the other CAPSs. Amyloidosis caused by chronic inflammation is the most serious complication of MWS and is seen in approximately one-third of patients, manifesting as proteinuria followed by renal impairment. Symptoms of MWS may occur daily but vary individually, are broad in intensity and duration, and can last 1 to 2 days before resolving spontaneously. The symptoms can result from metabolic stressors including cold, stress, and exercise, as well as microbial pathogens. Leukocytosis and increased acute-phase reactants are observed during episodes of inflammation.^4,6,8

Histopathology
Mild phenotypic variability exists between individuals, and many of the symptoms overlap in CAPSs. Although CAPSs display several distinguishing clinical characteristics, interestingly they share the same histopathological features regardless of the syndrome. The typical histopathological finding is a dermal neutrophilic infiltrate that tends to be perivascular and also may be perieccrine. Vasodilation and dermal edema also may be seen. These histopathological findings contrast with the typical lymphocytic and eosinophilic infiltrate seen in classic urticaria. Similar histopathologic findings have been seen in other neutrophilic urticarial dermatoses such as Schnitzler syndrome.^4,6

Differential
The differential diagnoses for CAPSs include Schnitzler syndrome, cold urticaria, systemic-onset juvenile idiopathic arthritis/adult-onset Still disease, and deficiency in IL-1ra. It is important to consider these differential diagnoses for management and treatment options.

Management
The discovery of the NLRP3 gene mutation as well as an understanding of IL-1 biology has led to targeted therapy for these syndromes. Cryopyrin-associated periodic syndromes are mediated by IL-1β with an in vivo rate 5 times higher than in healthy patients.⁴ The blockade of IL-1β results in complete resolution of symptoms.

In the last several years, anakinra, rilonacept, and canakinumab have shown efficacy in targeting IL-1β as receptor antagonists. Anakinra is a short-acting recombinant IL-1ra with a half-life of 4 to 6 hours. This short half-life requires daily injections and the most common adverse events included injection-site reaction and upper respiratory tract infection.^2,4 Rilonacept is a dimeric fusion protein that contains binding regions for the type 1 receptor and the IL-1 receptor accessory protein and is fused to the fragment, crystallizable (Fc) portion of human IgG1. Rilonacept is long acting with a circulating half-life of 8.6 days and offers patients ease of dosing with weekly subcutaneous injections. Rilonacept generally is well tolerated, with the most frequent adverse effects being injection-site reaction, upper respiratory tract infection, headache, arthralgia, and diarrhea.^2,7

The newest of the treatments for patients with CAPS is canakinumab. It is a fully human IL-1β monoclonal antibody that is specific for IL-1β and not other members of the IL-1 family. It has a mean half-life of 26 days and is dosed subcutaneously once every 8 weeks. The most common adverse effects include nasopharyngitis, rhinitis, nausea, diarrhea, and vertigo.⁴ In one study, most patients did not report injection-site reactions.⁷ Studies also are underway on VX-765, a caspace-1 targeted therapy that acts upstream in the IL-1β pathway. Treatment with anakinra, rilonacept, and canakinumab generally offers rapid and sustained remission in the majority of MWS patients and helps prevent the development of systemic amyloidosis and lessens the potential for end organ damage.^2,7

MWS and BCNS
Our patient had an unusual presentation of MWS complicated by BCNS, another rare autosomal-dominant inherited genodermatosis. In an extensive review of PubMed articles indexed for MEDLINE using the search terms Muckle-Wells syndrome and basal cell nevus syndrome, no association was identified between MWS and BCNS. Basal cell nevus syndrome is linked to PTCH1 (patched 1) gene mutation with an incidence of 1:150,000 in the United States and Europe and is characterized by a broad range of anomalies including skeletal abnormalities, ectopic calcification, odontogenic keratocysts, facial dysmorphism with macrocephaly, palmoplantar pits, and numerous tumors. Most notable is the early and strong predisposition to develop several to hundreds of BCCs.⁹

Conclusion

Muckle-Wells syndrome may go undiagnosed for many years or may be misdiagnosed as refractory urticaria, as in our patient. It is important to include periodic fever syndromes in the differential diagnosis of refractory urticaria with episodic fever to diagnose these cases of MWS earlier.