Acute eosinophilic lung disease secondary to drug reaction

Case Discussion

The patient had a history of recent antidepressant drug uptake one week before the start of acute low-grade fever, cough, dyspnea, and extensive widespread skin eczema.

CT scan of the chest revealed bilateral pulmonary mainly peripheral subpleural patches of ground glass attenuation, associated with smooth interlobular thickening, which was suggestive of eosinophilic lung disease.

CBC revealed marked absolute eosinophilia (14%).

Diagnosis of secondary (drug-induced) eosinophilic lung disease was made. The causative drug was stopped immediately and the patient received prednisolone therapy for 1 week after which he had a dramatic clinical improvement.

Eosinophilic lung diseases are a diverse group of pulmonary disorders associated with peripheral or tissue eosinophilia.

They are divided into three main groups

• idiopathic: unknown causes (simple pulmonary eosinophilia, acute eosinophilic pneumonia, chronic eosinophilic pneumonia, idiopathic hypereosinophilic syndrome)
• secondary: known causes (drugs, parasites, allergic bronchopulmonary aspergillosis, bronchocenteric granulomatosis)
• eosinophilic vasculitis: eosinophilic granulomatosis with polyangiitis(Churg-Strauss syndrome)

Diagnosis is made based on one of the following:

• pulmonary opacities on a chest radiograph or HRCT chest with peripheral eosinophilia
• tissue eosinophilia at either open or transbronchial lung biopsy
• increased eosinophils in bronchoalveolar lavage (BAL) fluid 

CT demonstrates a more characteristic pattern and distribution of parenchymal opacities as follows

• Simple pulmonary eosinophilia (SPE): transient areas of air-space consolidation which usually resolve spontaneously within 1 month. These consolidations are usually peripheral, may be single or multiple, and usually have ill-defined margins. Sometimes it might appear as airspace nodules with surrounding ground-glass opacity
• Acute eosinophilic pneumonia (AEP): bilateral patchy of ground-glass opacities, usually associated with interlobular septal thickening, sometimes consolidations or poorly defined nodules
• Chronic eosinophilic pneumonia (CEP): peripheral airspace consolidations with peripheral predominance, might be associated with ground glass opacities, nodules, or reticulations
• Idiopathic hypereosinophilic syndrome: pulmonary involvement is often non-specific and consists of focal or diffuse, interstitial or alveolar non-lobar opacities
• Allergic bronchopulmonary aspergillosis:  mucoid impaction and bronchiectasis involving predominantly the segmental and subsegmental bronchi of the upper lobes giving the gloved finger appearance
• Parasitic infections: consolidations, nodules, bronchiectasis
• Drug reactions: Patients with drug-induced eosinophilic lung disease can present with a variety of pathologic conditions ranging from a mild, SPE-like syndrome to a fulminant, AEP-like syndrome, airspace consolidations and ground glass opacities in a peripheral distribution
• Eosinophilic vasculitis (Churg-Strauss syndrome): The diagnosis of Churg-Strauss syndrome can be made if four or more of the following six findings are present: asthma, eosinophilia >10%, neuropathy, transient pulmonary opacities, paranasal sinus abnormalities, and extravascular eosinophils revealed at biopsy. CT findings include subpleural ground-glass opacities or consolidations with a lobular distribution, centrilobular nodules, bronchial wall thickening, and interlobular septal thickening