Occam's razor or Hickam's dictum? Allergic bronchopulmonary aspergillosis and eosinophilic granulomatosis with polyangiitis

Coexistence of Eosinophilic Granulomatosis With Polyangiitis and Allergic Bronchopulmonary Aspergillosis: A Fascinating Relationship

Elevated eosinophil counts are associated with various diseases, including eosinophilic granulomatosis with polyangiitis (EGPA) and allergic bronchopulmonary aspergillosis (ABPA). EGPA is a rare small-vessel vasculitis characterized by asthma, eosinophilia, fleeting pulmonary infiltrates, and systemic manifestations. ABPA, initiated by immune reactions against Aspergillus fumigatus in the airways, presents with poorly controlled asthma, wheezing, hemoptysis, productive cough, and systemic symptoms, which result in characteristic central bronchiectasis. Fleeting pulmonary opacities are common radiologic findings. We present a case of ABPA in a patient with a prior EGPA diagnosis under treatment with mepolizumab 300 mg monthly and review eight similar cases from the literature. In these cases, EGPA and ABPA diagnoses preceded each other or were concurrent. Treatment of the latter improved control of both diseases. IL-5 is pivotal in EGPA pathogenesis, and mepolizumab, targeting IL-5, has been effective in EGPA treatment. Our patient received mepolizumab for EGPA and continued it post-ABPA diagnosis, showing favorable outcomes. This suggests mepolizumab as a therapeutic link between EGPA and ABPA. Mepolizumab therapy holds promise for managing both EGPA and ABPA. Double-blind placebo-controlled studies are warranted to establish its efficacy and safety for ABPA, emphasizing the need for further research in this area.

[Vasculitides and eosinophilic pulmonary diseases]

Eosinophilic granulocytes form peripheral effector cells controlled by Th2 lymphocytes, which cause local cell, tissue, and functional disorders of infiltrated organs via the release of cytotoxic basic proteins and oxygen radicals. Diseases associated with eosinophilia include systemic and organ-related forms. The lungs are involved in eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome), acute and chronic eosinophilic pneumonia, as well as in an organ manifestation in hypereosinophilic syndrome and certain parasitic diseases. In particular, the lungs are frequently affected in vasculitis of small vessels, including EGPA, granulomatosis with polyangiitis (GPA), and microscopic polyangiitis (MPA). Among these, EGPA is the most frequent pulmonary eosinophil vasculitis representative. In addition, there are various overlap syndromes in which characteristic features of EGPA can be detected in the context of other anti-neutrophil cytoplasmic antibody (ANCA-)associated vasculitides. Occasionally, non-ANCA-associated pulmonary vasculitides occur with eosinophilia (e.g., Schönlein-Henoch purpura, Kawasaki disease, drug-induced hypersensitivity, and paraneoplastic syndrome). Herein, the pulmonary vasculitides accompanying eosinophilia are presented with respect to both the lung manifestations and pulmonary eosinophilia.

[Vasculitides and eosinophilic pulmonary diseases]

Eosinophilic granulocytes form peripheral effector cells controlled by Th2 lymphocytes, which cause local cell, tissue, and functional disorders of infiltrated organs via the release of cytotoxic basic proteins and oxygen radicals. Diseases associated with eosinophilia include systemic and organ-related forms. The lungs are involved in eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome), acute and chronic eosinophilic pneumonia, as well as in an organ manifestation in hypereosinophilic syndrome and certain parasitic diseases. In particular, the lungs are frequently affected in vasculitis of small vessels, including EGPA, granulomatosis with polyangiitis (GPA), and microscopic polyangiitis (MPA). Among these, EGPA is the most frequent pulmonary eosinophil vasculitis representative. In addition, there are various overlap syndromes in which characteristic features of EGPA can be detected in the context of other anti-neutrophil cytoplasmic antibody (ANCA-)associated vasculitides. Occasionally, non-ANCA-associated pulmonary vasculitides occur with eosinophilia (e.g., Schönlein-Henoch purpura, Kawasaki disease, drug-induced hypersensitivity, and paraneoplastic syndrome). Herein, the pulmonary vasculitides accompanying eosinophilia are presented with respect to both the lung manifestations and pulmonary eosinophilia.