Eosinophilic lung disease

Eosinophilic lung diseases comprise of a broad group of conditions and are broadly divided into 3 main groups ¹

• idiopathic : unknown causes
• secondary : known causes
• eosinophilic vasculitis : Churg-Strauss syndrome

Idiopathic

Simple pulmonary eosinophilia (SPE)

Simple pulmonary eosinophila (also known as Loffler syndrome) is benign and self-limiting condition, characterised by mild symptoms and plain radiographic findings usually much more impressive than the patient's condition, and classically have a reverse bat's wing appearance. Blood eosinophilia is a feature.

Acute eosinophilic pneumonia (AEP)

Acute eosinophilic pneumonia (AEP) usually manifests with fever, dyspnoea and hypoxia and shows with rapid improvement when treated with steroids. Pulmonary lavage reveals > 25% eosinophils. The etiology of AEP is unknown. It has been suggested that it may represent acute hypersensitivity to an inhaled antigen. CT findings include bilateral patchy areas of ground-glass opacity and interlobular septal thickening. 

Chronic eosinophilic pneumonia (CEP)

Chronic eosinophilic pneumonia is characterised by homogeneous peripheral airspace consolidation, which responds to steroid treatment. This appearance results in a reverse bat's wing appearance. About 50% of patients with CEP have asthma. CEP may be difficult to differentiate from Churg-Strauss syndrome (CSS). While CEP has homogeneous peripheral airspace consolidations, the consolidations in CSS tends to be more lobular in distribution. In addition, CSS tends to have centrilobular nodules. 

Idiopathic hypereosinophilic syndrome (IHS)

Idiopathic hypereosinophilic syndrome is a systemic disorder with damage to heart and the CNS. On CT, one finds nodules with a ground-glass halo, similar to SPE. In contrast to SPE, the opacities do not resolve spontaneously. In addition, approximately 50% of cases are associated with pleural effusions.

Secondary (of known cause)

Drugs

Non specific findings on chest radiography and CT.

• antibiotics
  • nitrofurantoin (which also progresses onto pulmonary fibrosis)
  • penicillin
  • tetracyclin
• toxins
  • eosinophilia-myalgia syndrome from Contaminated L-tryptophan
  • toxic oil syndrome

Infection

• fungal
• parasitic
  • schistosomiasis (50% have pulmonary involvement)
  • ascaris
  • toxocara canis
  • microfilariasis (tropical eosinophillia)
  • strongyloidasis

Allergic bronchopulmonary aspergillosis (ABPA)

ABPA is not a fungal infection, but rather a hypersensitivity response to fungal allergens. CT findings include bronchiectasis involving the central and upper lungs with or without mucoid impaction.

Bronchocentric granulomatosis (BG)

Bronchocentric granulomatosis (BG) is a rare disorder with non-specific radiographic findings. Approximately 2/3 of cases are not associated with tissue eosinophilia. The remaining 1/3 have peripheral eosinophilia, asthma, fungal hyphae at biopsy and positive sputum cultures for Aspergillus.

Eosinophillic vasculitis(des)

Churg-Strauss syndrome (CSS)

Churg Strauss syndrome (also known as allergic granulomatosis and angiitis), is associated with CT findings similar to CEP. Like CEP, CSS is seen in asthma patients. In contrast to CEP, the subpleural consolidations tend to have a lobular distribution and tend to be migratory or transient. In addition, centrilobular nodules are found on CT.