What are the expected cytology findings and management options for nasal polyps in patients with Eosinophilic Granulomatosis with Polyangiitis (EGPA)?

Cytology and Histopathology of Nasal Polyps in EGPA

Nasal polyps in EGPA are characterized by dense eosinophilic infiltration within the submucosa, but typically lack the classic vasculitis and granulomas seen in other affected tissues, making nasal biopsy alone insufficient for diagnosis.

Characteristic Cytological Findings in EGPA Nasal Polyps

Primary Histopathological Features

• Dense eosinophil-rich infiltrate within the submucosa (35-100% of cases) 1
• Marked tissue eosinophilia 1, 2
• Inflammatory changes consistent with chronic rhinosinusitis 1
• Neutrophil aggregates (more prevalent in EGPA than in chronic rhinosinusitis) 3

Notable Absences in Nasal Tissue

• Necrotizing vasculitis (rarely seen in nasal tissue despite being characteristic elsewhere) 1
• Extravascular granulomas (typically absent in sinonasal tissue) 1
• Classic EGPA triad (eosinophilic inflammation, extravascular granulomas, and necrotizing vasculitis) is incomplete in nasal polyps 1

Diagnostic Implications

Limitations of Nasal Polyp Biopsy

• Nasal polyp histology alone is insufficient for EGPA diagnosis 1
• Biopsies of sino-nasal mucosa/polyps are often non-diagnostic 3
• Lower diagnostic yield compared to other tissue types 1
• Prior steroid treatment may mask characteristic histological features 1

Correlation with Disease

• Nasal cytological eosinophilia correlates with tissue eosinophilia and clinical staging of nasal polyposis 2
• Hypereosinophilia is present in the majority of EGPA patients with nasal involvement 4
• Eosinophilic infiltration tends to be higher in patients with the triad of asthma, nasal polyposis, and NSAID intolerance 2

Management of Nasal Polyps in EGPA

Medical Management

1. Systemic Therapy:

   • Glucocorticoids are first-line therapy 3
   • Immunosuppressive agents for steroid-sparing effect 3
   • Mepolizumab (anti-IL-5 monoclonal antibody) is FDA-approved for EGPA 5
     • Dosage: 300 mg administered subcutaneously once every 4 weeks as 3 separate 100-mg injections 5

2. Topical Therapy:

   • Topical nasal corticosteroids should be optimized 3
   • Involvement of otolaryngologists is essential 3

Surgical Management

• Endoscopic sinus surgery may be effective for rhinosinusitis associated with EGPA when medical therapy fails 6
• Surgery may help control symptoms and improve quality of life 6

Clinical Pearls and Pitfalls

Pearls

• Nasal cytology is a simple, fast, non-traumatic, and inexpensive method for evaluating eosinophilia in nasal polyps 2
• Over 85% of EGPA patients demonstrate nasal symptoms 7
• EGPA patients show a significantly higher incidence of nasal polyps than those with GPA 7

Pitfalls

• Relying solely on nasal polyp histopathology for EGPA diagnosis will lead to false negatives 1
• Even when EGPA is "under control" according to vasculitis activity scores, sinonasal disease may remain active 4
• Nasal symptoms significantly impact quality of life in EGPA patients and require targeted treatment 4

Monitoring and Follow-up

• Routine monitoring of EGPA-related manifestations is recommended 3
• Nasal cytology can be used to monitor disease activity and response to treatment 2
• Collaboration between rheumatologists, pulmonologists, and otolaryngologists is essential for comprehensive management 3

Remember that a low threshold of suspicion is required for EGPA in any patient with eosinophilic diseases (significant adult-onset asthma, recurrent CRSwNP, and allergic rhinitis) 3, as early diagnosis and treatment can significantly improve morbidity and mortality outcomes.