Differentials
Granulomatosis with polyangiitis (GPA) (formerly known as Wegener's granulomatosis)
SIGNS / SYMPTOMS
Absence of asthma or eosinophilia. Peripheral neuropathy is more common in EGPA.
INVESTIGATIONS
FBC with differential will typically show no eosinophilia in GPA.
Pulmonary function testing will typically show airway reversibility in EGPA, but not in GPA or microscopic polyangiitis; it may be normal in GPA or show evidence of extrathoracic airway obstruction in cases of subglottic stenosis. Alveolar haemorrhage and glomerulonephritis are relatively rare in EGPA but common in GPA. Alveolar haemorrhage may be associated with a gas exchange abnormality.
Microscopic polyangiitis (MPA)
SIGNS / SYMPTOMS
Absence of asthma. Peripheral neuropathy is more common in EGPA.
INVESTIGATIONS
FBC with differential will typically show no eosinophilia in MPA.
Pulmonary function testing will typically be normal in MPA. If there is concurrent pulmonary fibrosis, restrictive changes may be seen.
Alveolar haemorrhage and glomerulonephritis are relatively rare in EGPA, but common in MPA. Alveolar haemorrhage may be associated with a gas exchange abnormality.
Hypereosinophilic syndrome (HES)
SIGNS / SYMPTOMS
Absence of asthma or of clinical vasculitis such as palpable purpura, petechiae.
INVESTIGATIONS
Flow cytometry of peripheral blood may be abnormal. Molecular testing for the FIP1L1/PDGFR alpha mutation may be positive in HES. Renal failure is more common in EGPA.
Parasitic disorders
SIGNS / SYMPTOMS
Absence of asthma or of clinical vasculitis such as palpable purpura, petechiae.
INVESTIGATIONS
Stool studies are positive in helminthic infections. Renal failure is uncommon in parasitic disorders.
Allergic bronchopulmonary aspergillosis
SIGNS / SYMPTOMS
Absence of clinical vasculitis such as palpable purpura, petechiae.
INVESTIGATIONS
The presence of skin test reactivity to Aspergillus antigens or serum antibodies to Aspergillus fumigatus. Renal failure is uncommon in allergic bronchopulmonary aspergillosis.
Chronic eosinophilic pneumonia
SIGNS / SYMPTOMS
Absence of clinical vasculitis such as palpable purpura, petechiae.
Typically occurs in women and non-smokers. May be seen in women undergoing radiotherapy for breast cancer.
INVESTIGATIONS
Bronchoalveolar lavage with >40% eosinophils is suggestive of eosinophilic pneumonia. Biopsy differentiates from EGPA. Presence of vasculitis is seen in EGPA in addition to presence of eosinophils. Chest x-ray shows a pattern termed a photographic negative picture of pulmonary oedema. Renal failure is more common with EGPA.
Severe asthma
SIGNS / SYMPTOMS
Absence of signs or symptoms of clinical vasculitis such as palpable purpura, petechiae.
INVESTIGATIONS
Absence of a positive anti-neutrophil cytoplasmic antibody.
No active urinary sediment.
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