INTRODUCTION — The Churg-Strauss syndrome (CSS), also called allergic granulomatosis and angiitis, is a multisystem disorder characterized by allergic rhinitis, asthma, and prominent peripheral blood eosinophilia [1-6]. CSS is classified as a vasculitis of the small and medium sized arteries, although the vasculitis is often not apparent in the initial phases of the disease.
The most commonly involved organ is the lung, followed by the skin. CSS, however, can affect any organ system, including the cardiovascular, gastrointestinal, renal, and central nervous systems. Vasculitis of extrapulmonary organs is largely responsible for the morbidity and mortality associated with CSS.
The diagnosis of CSS is typically suspected based on the clinical findings (ie, eosinophilia ≥1500/microL, asthma, and allergic rhinitis). A positive antineutrophil cytoplasmic antibody test is present in 40 to 60 percent, but is neither sensitive nor specific. The diagnosis is generally confirmed by a biopsy of an affected tissue, such as lung, skin or peripheral nerve [1-4] (table 1).
The treatment and prognosis of CSS will be reviewed here. The epidemiology, pathogenesis, clinical features, and diagnosis of this disorder are discussed separately. (See "Epidemiology, pathogenesis, and pathology of Churg-Strauss syndrome (allergic granulomatosis and angiitis)" and "Clinical features and diagnosis of Churg-Strauss syndrome (allergic granulomatosis and angiitis)".)
ASSESSING VASCULITIS SEVERITY — Two scoring systems have been developed to assess vasculitis disease activity in patients with CSS and other vasculitides: the "five factors score" and the Birmingham Vasculitis Activity Score (BVAS). These scoring systems are used to guide initial therapy.
The "five-factors score" (FFS) is based on the presence or absence of the following five clinical factors [5]:
The presence of each factor is given one point. The FFS score ranges from 0 to 2: a score of 0 is given when none of the factors are present, a score of 1 for one factor, and a score of 2 for two or more factors. This scoring system has also been correlated with prognosis. (See 'Prognosis' below.)
The Birmingham Vasculitis Activity Score (BVAS) is a research tool that is seldom used in clinical practice [7]. It has largely been applied to patients with granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis, but has also been used in CSS [6,8]. The score includes both general symptoms (arthralgia, arthritis, and fever) and involvement of eight major organ systems (skin, mucous membranes, ear/nose/throat, cardiovascular, pulmonary, gastrointestinal, renal, nervous system) [7]. At each site, persistent symptoms or manifestations (eg, sensorineural deafness, pulmonary nodule, alveolar hemorrhage) are given one point and new or worse symptoms are given two points. The score ranges from 0 (complete remission) to a maximum of 68. (See "Initial immunosuppressive therapy in granulomatosis with polyangiitis (Wegener's) and microscopic polyangiitis", section on 'Assessment of disease activity'.)
INITIATING THERAPY — The primary therapy for CSS is systemic glucocorticoids. An additional immunosuppressive agent is typically added in patients with more advanced or refractory disease and in those whose disease flares with tapering of systemic glucocorticoids [9]. Choosing among these agents is largely dependent on the disease severity and response to treatment. (See 'Assessing vasculitis severity' above.)
Asthma is additionally managed according to current guidelines, as described separately. (See "An overview of asthma management", section on 'Pharmacologic treatment' and "Treatment of severe asthma in adolescents and adults", section on 'Adjusting controller therapy'.)
Hypertension should be managed in a standard fashion, but is sometimes difficult to control [1,10]. (See "Overview of hypertension in adults" and "Choice of therapy in essential hypertension: Recommendations".)
Systemic glucocorticoids — Systemic glucocorticoid therapy is the mainstay of treatment for CSS. For patients with evidence of systemic vasculitis, treatment is initiated with prednisone (or the equivalent) at a dose of 0.5 to 1.5 mg/kg per day. The higher dose is used for patients with more severe vasculitis (eg, impending respiratory failure, cardiac involvement, glomerulonephritis, neuropathy). With acute multiorgan disease, intravenous glucocorticoid (eg, methylprednisolone 1 g daily for three days) is used for initial therapy, followed by oral glucocorticoid therapy as noted [2,3].
The majority of patients with CSS achieve a remission with glucocorticoid therapy alone [11]. In a study of 72 patients without poor-prognosis factors (ie, no cardiac, renal or central nervous system involvement) followed for five years or longer, 93 percent achieved a remission with glucocorticoid therapy alone [11]. However, patients with involvement of the heart, kidney, gastrointestinal tract, or central nervous system will usually require additional immunosuppressive therapy as described below.
Once disease manifestations have come under control, the glucocorticoid dose is gradually tapered over approximately 12 to 18 months, as tolerated. A portion of patients will need long-term low dose oral glucocorticoid therapy (eg, prednisone 10 mg/day or less). In the study of 72 patients described above, almost 80 percent of those who achieved a remission required long-term low-dose glucocorticoid therapy [11].
In CSS, late relapses of systemic vasculitis after a successful response to treatment are uncommon [12]. However, premature withdrawal of treatment can result in recurrence.
Cyclophosphamide — Cyclophosphamide is typically used in combination with glucocorticoids for patients with severe, multiorgan disease [5,13-20]. The decision to add cyclophosphamide is based on the severity of disease in terms of number of organ systems involved and degree of impairment. The five factors score (FFS) is used to quantitate the extent of disease and guide therapy (table 2). (See 'Assessing vasculitis severity' above.)
Cyclophosphamide may be administered orally every day or intravenously once a month [18]. Insufficient data is available for CSS to make a clear recommendation regarding this choice. Extrapolating from granulomatosis with polyangiitis (Wegener’s), outcomes with daily and monthly regimens were similar; a slightly greater risk of bladder toxicity with the daily regimen and a slightly greater risk of relapse with the monthly regimen have been noted. (See "Initial immunosuppressive therapy in granulomatosis with polyangiitis (Wegener's) and microscopic polyangiitis", section on 'Initial therapy'.)
Dosing and monitoring considerations for daily and monthly administration of cyclophosphamide are described separately. (See "General principles of the use of cyclophosphamide in rheumatic and renal disease".)
The duration of cyclophosphamide therapy remains controversial. When used to treat granulomatosis with polyangiitis, typically a six month regimen is used. However, in a preliminary study of patients with CSS, those receiving 6 pulses of cyclophosphamide had more relapses than those receiving 12 pulses (94 percent versus 41 percent) [20]. Further data is needed to clarify whether the benefits of 12 pulses of cyclophosphamide outweigh the additional risks. (See "General toxicity of cyclophosphamide and chlorambucil in inflammatory diseases".)
MAINTENANCE AND GLUCOCORTICOID SPARING THERAPY — Once remission is induced with cyclophosphamide and glucocorticoid therapy (which usually occurs within six to twelve months), patients are switched to maintenance therapy with less toxic immunosuppressive drugs, usually azathioprine or methotrexate, in combination with a tapering dose of glucocorticoids.
For patients whose disease is not severe enough to require cyclophosphamide, but requires long-term therapy with moderate to high dose prednisone (eg, more than 10 mg daily), an immunosuppressive agent is often added for a glucocorticoid sparing effect. The data in support of this comes from clinical experience and extrapolation from the management of granulomatosis with polyangiitis (Wegener’s). (See "Maintenance immunosuppressive therapy in granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis".)
Maintenance immunosuppressive therapy is typically continued for 12 to 18 months. Longer term or indefinite maintenance therapy may be warranted in patients with multiple relapses.
Azathioprine — In patients with CSS, azathioprine (AZA) is typically used after induction of remission with cyclophosphamide or as a glucocorticoid-sparing agent in patients requiring long-term treatment with prednisone at doses greater than 15 mg per day [11,22,23]. Analysis of the thiopurine methyltransferase (TPMT) gene prior to the administration of AZA may help predict those individuals at risk for severe toxicity. When deficiency of the TPMT enzyme is found, we choose an alternate immunosuppressive agent, such as methotrexate or mycophenolate, although data regarding the use of these agents is limited. (See "Pharmacology and side effects of azathioprine when used in rheumatic diseases", section on 'Pharmacogenetics'.)
Different regimens have been reported for initiation of AZA: starting with the target dose of 2 mg/kg lean body weight versus starting at 25 to 50 mg/day for the first week to test for drug hypersensitivity and then increasing by 0.5 mg/kg per day every four to six weeks up to the target dose. In general, we favor going directly to the target dose in order to avoid a relapse during the time that the patient is on suboptimal doses. The direct approach was used successfully in a trial of patients with granulomatosis with polyangiitis [24]. A lower target dose is indicated in patients with renal insufficiency. (See "Maintenance immunosuppressive therapy in granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis", section on 'Azathioprine' and "Pharmacology and side effects of azathioprine when used in rheumatic diseases", section on 'Drug dosage and monitoring'.)
Following the pattern established for granulomatosis with polyangiitis, the timing of initiation of maintenance AZA is based on whether the patient was on daily or monthly dosing of cyclophosphamide. For patients on daily dosing, the switch is immediate; for those on monthly dosing, AZA is begun approximately two weeks after the last dose of cyclophosphamide. This is delayed further if the white blood cell count is below 4000 cells/microL, or the absolute neutrophil count is below 1500 cells/microL. (See "Maintenance immunosuppressive therapy in granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis", section on 'Initiation of maintenance therapy'.)
Methotrexate — Methotrexate is sometimes used in CSS to maintain a remission after induction with cyclophosphamide or as a glucocorticoid-sparing agent. However, azathioprine is generally preferred over methotrexate because it is difficult to monitor for methotrexate pneumonitis in a patient with other causes of dyspnea, such as asthma and pulmonary eosinophilia.
Data regarding the use of methotrexate for maintenance of remission in CSS are limited. In a case series of 25 patients with CSS, methotrexate was associated with relapse rate of 48 percent, when used for maintenance [25]. On the hand, the prednisone dose was decreased by an average of 50 percent in these patients.
Methotrexate is occasionally used as an alternative to cyclophosphamide to induce a remission in patients with a five factors score (FFS) of 1 and mild disease. This is discussed in the section on initiating therapy. (See 'Cyclophosphamide' above.)
The dosing regimen for methotrexate comes from the larger experience using this medication in patients with Wegener's granulomatosis. The typical dose is 0.3 mg/kg per week (maximum dose 15 mg), given orally. If tolerated, the dose is increased in 2.5 mg increments each week to a dose of 20 to 25 mg per week. Patients are also treated with daily folic acid 1 mg/day or leucovorin (2.5 to 5 mg) once per week given 24 hours after methotrexate. (See "Maintenance immunosuppressive therapy in granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis", section on 'Methotrexate' and "Major side effects of low-dose methotrexate".)
Methotrexate should be avoided in patients with an estimated creatinine clearance less than 50 mL/min and is contraindicated during pregnancy.
Inhaled glucocorticoids — Inhaled glucocorticoids are typically used to help control upper and lower respiratory tract disease. Asthma management follows the guidelines outlined separately. (See "An overview of asthma management", section on 'Pharmacologic treatment' and "Treatment of severe asthma in adolescents and adults", section on 'Adjusting controller therapy'.)
OTHER THERAPIES — Second line treatment options may be considered when patients have disease refractory to the above-described conventional therapy or have therapy-limiting side effects. The data in support of these agents is limited to case reports and small case series.
Mycophenolate mofetil — A case report described successful use of mycophenolate mofetil plus oral glucocorticoids to treat a patient with CSS manifest by asthma, chronic rhinosinusitis, cutaneous vasculitis, and a positive ANCA (pANCA with antibodies to myeloperoxidase [MPO]) [26]. Dosing and potential side effects of mycophenolate are discussed separately. (See "Mycophenolate mofetil: Pharmacology and adverse effects when used in the treatment of rheumatic diseases".)
Intravenous immune globulin — Several case series have reported improvement in disease control in patients with refractory disease after addition of high-dose intravenous immune globulin to glucocorticoids with or without cyclophosphamide [6,27,28]. (See "General principles in the use of immune globulin".)
Hydroxyurea — Hydroxyurea, an agent that is used in the treatment of the hypereosinophilic syndrome, was found to be beneficial as a glucocorticoid-sparing agent in a patient with CSS [29]. Hydroxyurea has relatively few side effects compared to other chemotherapeutic agents, although hematological toxicity and gastrointestinal side effects may occur at higher doses. (See "Treatment of the hypereosinophilic syndromes".)
Rituximab — A few case reports have described some improvement in CSS after treatment with rituximab, an anti-CD20 monoclonal antibody [30-32]. However, rituximab appeared to cause immediate and severe bronchospasm in two patients with ANCA-negative CSS [33]. (See "Overview of biologic agents in the rheumatic diseases", section on 'B cell depletion'.)
Interferon-alpha — Several patients with disease unresponsive to glucocorticoids and cyclophosphamide have improved with a regimen of glucocorticoids and interferon-alpha [8,23]. This medication has also been used as a second line agent for patients with the hypereosinophilic syndrome. (See "Treatment of the hypereosinophilic syndromes", section on 'Interferon alfa'.)
Anti-IgE therapy — A case report described a patient with CSS and nonallergic asthma, whose asthma was refractory to systemic and inhaled glucocorticoid and long-acting beta agonists; asthma control improved with anti-IgE (omalizumab) therapy [34]. Another report described similar results with anti-IgE in two patients whose CSS was not controlled by systemic glucocorticoid [35]. Omalizumab may have a pro-apoptotic effect on eosinophils.
Conversely, a temporal association between omalizumab use and the development of CSS has been reported [36]. Further studies of safety and efficacy are needed before this approach can be recommended. (See "Anti-IgE therapy".)
Anti-IL-5 antibodies — Mepolizumab is a humanized monoclonal antibody to interleukin (IL)-5 that appears to have a glucocorticoid sparing effect in patients with hypereosinophilic syndrome. (See "Treatment of the hypereosinophilic syndromes", section on 'Anti-IL-5'.)
The efficacy of mepolizumab in the treatment of CSS has been assessed as follows:
Plasma exchange — Plasma exchange occasionally has been used in conjunction with other therapies, but a meta-analysis involving 140 patients with glomerulonephritis due to CSS or microscopic polyangiitis found that it added no benefit to treatment with glucocorticoids, with or without cyclophosphamide [40]. (See "Indications for therapeutic plasma exchange".)
PREVENTION OF TREATMENT RELATED COMPLICATIONS — The predominant complications of the immunosuppressive and glucocorticoid therapy described above are opportunistic infections and glucocorticoid-related osteoporosis, cataracts, and adrenal suppression; appropriate prophylaxis can help to prevent some of these complications [19].
We suggest Pneumocystis prophylaxis for patients who are on a combination of high-dose glucocorticoid (eg, prednisone 20 mg/day or more) and another immunosuppressive agent. (See "Treatment and prevention of Pneumocystis pneumonia in non-HIV-infected patients", section on 'Prophylaxis'.)
Prevention of other complications of chronic systemic glucocorticoid therapy is discussed separately. (See "Major side effects of systemic glucocorticoids" and "Prevention and treatment of glucocorticoid-induced osteoporosis".)
Mercaptoethane sulfonate (MESNA) is typically used to reduce bladder toxicity during infusions of cyclophosphamide [2]. (See "General principles of the use of cyclophosphamide in rheumatic and renal disease", section on 'Preventing drug-induced cystitis'.)
Analysis of the thiopurine methyltransferase (TPMT) gene prior to the administration of AZA may help predict those individuals at risk for severe toxicity. (See 'Azathioprine' above.)
MONITORING — Monitoring responsiveness to treatment and the development of recurrence is best achieved by following symptoms, the eosinophil count, spirometry, and any previously abnormal laboratory parameters. Radiographic manifestations may remain stable or may rapidly regress with glucocorticoid treatment. Renal function should be monitored by urinalysis and measurement of serum creatinine. We typically reassess patients at three month intervals, sooner if they experience any change in clinical status.
Persistence of ANCA positivity in CSS may be a marker of an underlying disease process, but does not appear to adequately reflect disease activity and, thus, cannot be used by itself to determine changes in therapy [41,42]. (See "Relapsing disease in granulomatosis with polyangiitis (Wegener’s) and microscopic polyangiitis", section on 'ANCA titers'.)
SPECIAL CONSIDERATIONS
Upper airway involvement — Nasal and otologic complications of CSS typically require intranasal glucocorticoids and intermittent courses of antibiotics and systemic glucocorticoids [43,44]. Some patients will also require more long-term systemic glucocorticoid therapy and sometimes also immunosuppressive therapy. In addition, surgical approaches, such as functional endoscopic sinus surgery for nasal polypectomy or myringotomy with ventilation tube placement for refractory otitis, may be necessary. When possible, we try to manage the upper airway complications of CSS with local therapy and intermittent courses of systemic glucocorticoids. (See "Medical management of chronic rhinosinusitis", section on 'CRS with nasal polyposis'.)
The role of leukotriene modifying agents (LTMA) in the management of asthma and nasal polyposis in patients with CSS is unclear, due to the reports of CSS developing in the context of LTMA therapy. In patients with asthma, nasal polyposis, and CSS who have not previously taken an LTMA, we often add an LTMA to the regimen, as described for patients with aspirin exacerbated respiratory disease. (See "Epidemiology, pathogenesis, and pathology of Churg-Strauss syndrome (allergic granulomatosis and angiitis)", section on 'Association with medications' and "Aspirin exacerbated respiratory disease", section on 'Leukotriene modifying agents'.)
Pregnancy — Treatment of vasculitis during pregnancy is complicated due to adverse fetal effects of immunosuppressive medications. As examples, cyclophosphamide and azathioprine are teratogenic and methotrexate is an abortifacient. Systemic glucocorticoids are relatively safer, but may not control active vasculitis. Approaches to the treatment of vasculitis during pregnancy are discussed separately. (See "Initial immunosuppressive therapy in granulomatosis with polyangiitis (Wegener's) and microscopic polyangiitis", section on 'Management in pregnancy'.)
PROGNOSIS — The prognosis of patients with CSS has improved significantly since the widespread use of systemic glucocorticoids. Prior to the use of glucocorticoids, for example, the disease was uniformly fatal, with 50 percent of untreated patients dying within three months of the onset of vasculitis. In comparison, most modern clinical series suggest a survival rate of greater than 70 percent at five years [45,46].
Most deaths result from complications of the vasculitic phase of the disease, and are most commonly due to:
The presence or absence of the features that make up the "five-factor score" has been used to predict survival in CSS (ie, cardiac involvement, gastrointestinal disease (bleeding, perforation, infarction, or pancreatitis), renal insufficiency (plasma creatinine concentration >1.6 mg/dL [141 micromol/L]), proteinuria (>1 g/day), central nervous system involvement) [5,19]. One large series reported the following 5-year mortality figures [5]:
Of the "five factors", cardiac involvement and gastrointestinal disease appear to be the strongest indicators of poor prognosis [45]. The role of ANCA measurements in predicting outcome is not known.
SUMMARY AND RECOMMENDATIONS
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