American Board of Internal Medicine (ABIM) Certification Practice Exam

Which autoantibody is often present in Churg-Strauss syndrome?

1. Anti-dsDNA

2. Rheumatoid factor

3. P-ANCA / Myeloperoxidase (MPO)-ANCA

4. Anti-Smith

The correct answer is: P-ANCA / Myeloperoxidase (MPO)-ANCA

Churg-Strauss syndrome, also known as eosinophilic granulomatosis with polyangiitis, is a small-to-medium vessel vasculitis associated with asthma, eosinophilia, and systemic vasculitis affecting multiple organs. One of the hallmark features of this condition is the presence of specific autoantibodies, prominently the perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) that are directed against myeloperoxidase (MPO). The presence of p-ANCA/MPO-ANCA in Churg-Strauss syndrome is considered a significant marker for the disease, as it helps in both the diagnosis and monitoring of the condition. This autoantibody is typically associated with small vessel vasculitis and is indicative of the underlying immunological processes that characterize the syndrome. Therefore, the identification of p-ANCA/MPO-ANCA can provide critical information about the patient's condition and the inflammation present. In contrast, the other autoantibodies mentioned—such as anti-dsDNA, rheumatoid factor, and anti-Smith—are more specific to other autoimmune disorders. For example, anti-dsDNA is primarily associated with systemic lupus erythematosus, rheumatoid