Churg-Strauss Syndrome: An Informative USMLE Guide

Introduction

Churg-Strauss Syndrome (CSS), also known as eosinophilic granulomatosis with polyangiitis (EGPA), is a rare autoimmune disorder characterized by inflammation of blood vessels. This USMLE guide aims to provide a comprehensive overview of CSS, including its clinical features, diagnostic criteria, pathophysiology, management, and prognosis.

Clinical Features

CSS primarily affects the small to medium-sized blood vessels, leading to multisystem involvement. The clinical features can be divided into three stages:

1. Prodromal Phase: Patients may experience constitutional symptoms such as fever, weight loss, fatigue, and myalgias.

2. Eosinophilic Phase: Eosinophilia is a hallmark of CSS, with peripheral eosinophil count often exceeding 10%. Patients may develop asthma, rhinitis, sinusitis, and pulmonary infiltrates. Skin involvement, such as purpura, nodules, and livedo reticularis, is also common.

3. Vasculitic Phase: This phase is characterized by systemic vasculitis affecting various organs. It can involve the heart (myocarditis, pericarditis), gastrointestinal tract (abdominal pain, mesenteric ischemia), kidneys (glomerulonephritis), nervous system (mononeuritis multiplex), and other organs.

Diagnostic Criteria

The following criteria, established by the American College of Rheumatology, are used for diagnosing Churg-Strauss Syndrome:

1. Asthma
2. Eosinophilia (>10%)
3. Systemic vasculitis (two or more of the following):
   • Peripheral neuropathy or mononeuritis multiplex
   • Non-fixed pulmonary infiltrates on imaging
   • Paranasal sinus abnormality (sinusitis)
   • Biopsy showing blood vessel inflammation with eosinophils

Pathophysiology

The exact cause of CSS remains unknown, but it is believed to involve a complex interplay of genetic and environmental factors. It is thought to result from an inappropriate immune response, leading to the activation of eosinophils and subsequent damage to blood vessel walls. Elevated levels of interleukin-5 (IL-5) and other cytokines contribute to eosinophil proliferation and recruitment.

Management

The management of CSS typically involves a multidisciplinary approach with rheumatologists, pulmonologists, and other specialists. The goals of treatment include controlling inflammation, suppressing the immune system, and managing organ-specific complications.

1. Glucocorticoids: High-dose systemic corticosteroids (e.g., prednisone) are the mainstay of treatment to control inflammation. Tapering the dose over time is necessary to minimize side effects.

2. Immunosuppressive Agents: For patients with severe or refractory disease, additional immunosuppressive agents such as cyclophosphamide, azathioprine, or methotrexate may be used.

3. Biologic Agents: Monoclonal antibodies targeting specific cytokines, such as mepolizumab (anti-IL-5) or benralizumab (anti-IL-5 receptor), have shown promise in reducing eosinophilic inflammation.

4. Organ-Specific Management: Specific complications, such as cardiac involvement or neuropathy, may require tailored interventions by respective specialists.

Prognosis

The prognosis of CSS has improved significantly with early diagnosis and treatment. However, CSS can still have a relapsing and remitting course. Mortality rates vary based on organ involvement but have decreased with the advent of immunosuppressive therapies. Regular follow-up and monitoring of organ function are crucial for long-term management.

Conclusion

Churg-Strauss Syndrome, also known as eosinophilic granulomatosis with polyangiitis, is a rare autoimmune disorder characterized by inflammation of blood vessels. This USMLE guide has provided an overview of the clinical features, diagnostic criteria, pathophysiology, management, and prognosis of CSS. Understanding this condition is vital for medical professionals to recognize, diagnose, and treat patients effectively.