Churg-Strauss Syndrome

What is Churg-Strauss Syndrome?

Churg-Strauss Syndrome, now formally known as Eosinophilic Granulomatosis with Polyangiitis (EGPA), is a rare necrotizing vasculitis of small- and medium-sized blood vessels. It typically affects the lungs, skin, nerves, and heart. This condition usually emerges in middle adulthood in patients with a history of adult-onset asthma and chronic rhinosinusitis.

The eponym honors Jacob Churg and Lotte Strauss, who first described the classic triad of asthma, high eosinophil counts, and vasculitis. In older medical literature, the condition is sometimes called Churg Strauss Disease. The incidence is approximately 1 to 4 cases per million people, with a peak onset between the ages of 38 and 50.

What causes Churg-Strauss Syndrome?

The pathogenesis of Churg-Strauss Syndrome centers on aberrant eosinophil activation and the release of Th2 cytokines. In many cases, MPO-ANCA-mediated neutrophil degranulation also contributes to the injury of vessel walls. Activated eosinophils release cytotoxic granule proteins, while interleukin-5 (IL-5) promotes eosinophil production and survival. These substances amplify tissue necrosis, particularly in the lungs and peripheral nerves.

A high “atopy burden” (a genetic tendency to develop allergic diseases), exposure to silica, and the initiation of leukotriene modifiers have been associated with the onset of EGPA, possibly by unmasking disease during corticosteroid tapering. A rapid rise in blood eosinophil counts often serves as a clinical herald, signaling that the condition is moving into its dangerous vasculitic phase.

What are the signs and symptoms of Churg-Strauss Syndrome?

The prodromal Churg-Strauss syndrome symptoms often mimic severe asthma and allergic rhinosinusitis, characterized by recurrent sinusitis, nasal polyps, and chronic wheezing. This is followed by the eosinophilic phase, where peripheral blood counts of eosinophils rise ≥1×10⁹/L. During this time, pulmonary infiltrates (substances denser than air in the lungs) may appear on imaging, often resolving or migrating to different areas of the lung.

During the vasculitic phase, painful mononeuritis multiplex (nerve damage in at least two separate nerve areas), palpable purpura (purple skin spots), and digital ischemia (reduced blood flow to fingers or toes) signal vessel involvement. Cardiac manifestations, such as eosinophilic myocarditis or coronary arteritis, are serious complications. Gastrointestinal involvement can cause abdominal pain and bleeding, while renal injury may present as focal necrotizing glomerulonephritis.

How is Churg-Strauss Syndrome diagnosed?

Clinicians suspect a Churg-Strauss diagnosis when asthma, high eosinophil levels, and systemic symptoms coexist. They typically check the individual’s ANCA (antineutrophil cytoplasmic antibody) status. Laboratory findings often show peripheral eosinophilia exceeding 1500 cells/μL, and serum IgE levels may be markedly elevated (often >1000 IU/mL). Chest CT scans may reveal migrating pulmonary nodules or ground-glass opacities.

Biopsy of an affected organ, such as the skin or lung, to demonstrate eosinophil-rich necrotizing vasculitis and granulomas, strongly supports the diagnosis but is not required if the clinical features are typical. The 2022 ACR/EULAR classification criteria provide a scoring system based on weighted features, including eosinophilia, obstructive airway disease, nasal polyps, neuropathy, and histologic evidence of eosinophilic inflammation. ANCA positivity, specifically anti-MPO, occurs in 30% to 40% of cases and offers important prognostic clues.

How is Churg-Strauss Syndrome treated?

Initial Churg-Strauss syndrome treatment almost always begins with high-dose glucocorticoids (steroids) to quickly quell eosinophilic inflammation. For individuals with life-threatening features or organ involvement, clinicians add immunosuppressants like cyclophosphamide or rituximab to lower the risk of relapse.

Once remission is achieved, the treatment plan shifts to maintenance therapy using steroid-sparing agents such as azathioprine, methotrexate, or mycophenolate. Mepolizumab, an anti-IL-5 monoclonal antibody, is increasingly used to reduce glucocorticoid exposure in refractory or relapsing cases. Throughout treatment, bronchodilators and inhaled steroids remain essential for managing the underlying asthma. Cardiac involvement may require specialized heart failure therapy and anticoagulation if intracardiac thrombi (clots) are detected.

What are the most important facts to know about Churg-Strauss Syndrome?

• EGPA, the modern term for Churg-Strauss Syndrome, is a necrotizing vasculitis that typically follows a history of adult-onset asthma.
• The disease process is driven by IL-5-mediated eosinophilia and, in some cases, MPO-ANCA neutrophil activation.
• Churg-Strauss syndrome symptoms progress through phases: starting with asthma, moving to migratory pulmonary opacities, and ending with systemic vasculitis, like mononeuritis multiplex.
• A Churg-Strauss diagnosis is supported by blood tests showing high eosinophils and confirmed by a biopsy demonstrating characteristic granulomas and vessel inflammation.
• Churg-Strauss syndrome treatment requires high-dose steroids initially, often combined with rituximab or mepolizumab to maintain long-term remission and protect vital organs.