Pictorial Essay Eosinophilic Lung Diseases: Findings that a Radiologist Should Know Juliana Couture1 Daniel Adri1 Juan Manuel Villegas1 Natalia Posadas1 Alberto Seehaus1 1 Imaging Diagnosis Department, Hospital Italiano de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina Abstract Eosinophilic lung diseases include a broad spectrum of disorders. The final diagnosis of these diseases is made by patho- logical examination. However, medical history, physical examination and imaging studies allow better characterization of the condition. At present, high-resolution multislice computed tomography (MSCT) is the most sensitive and specific imaging method, since it allows an accurate assessment of diffuse pulmonary pathology, thus avoiding more invasive methods, providing detailed information and depicting lesions that have no specific clinical presentation by means of characteristic imaging patterns. Keywords Hypereosinophilic syndrome, Multislice computed tomography, Pulmonary eosinophilia Introduction depicts lesions that have no specific clinical presentation.7 The most characteristic MSCT findings of eosinophilic syn- Eosinophilic lung diseases are infectious and non-infectious dromes will be discussed below (Table 1). disorders associated with peripheral eosinophilia (a marker of pathology, exceeding 0.5 × 109/L)1,2 with tissue eosino- philia confirmed by pulmonary biopsy or an elevated eosino- Idiopathic eosinophilic lung diseases philic count (25%) in bronchoalveolar lavage (BAL) 3-5. These diseases may be classified as: idiopathic (acute eosinophilic Loeffler syndrome or simple pulmonary pneumonia, chronic eosinophilic pneumonia and idiopathic eosinophilia hypereosinophilic syndrome), secondary to an infectious This is an entity of unknown cause that is characterized by an cause (aspergillus fumigatus) or associated with vasculitis and absence of symptoms or, if present, they are mild and non- granulomatosis (Churg-Strauss syndrome, granulomatosis specific (cough, dyspnea and low-grade fever) with resolution with polyangiitis, bronchocentric granulomatosis or Sjögren within one month. Plain radiography shows patchy opacities disease).5 High-resolution multislice computed tomography with a peripheral distribution. MSCT findings include ground- (MSCT)with a slice thickness of less than 1.5 mm , is the im- glass or consolidative opacities with peripheral satellite nod- aging method of choice for an accurate assessment of diffuse ules and bronchial wall thickening. Pleural effusions and pulmonary disease, because it has a higher sensitivity and lymphadenopathy do not occur.2 specificity than conventional radiology.6 Pulmonary biopsy if the gold standard method for diagnosis, but some time is re- Acute eosinophilic pneumonia (AEP) placed by BAL.6 In these syndromes, pulmonary involvement As the name indicates, AEP is characterized by a rapidly pro- is common. However, in early stages, imaging findings may gressive infiltration of eosinophils into the lungs, leading to be subtle; therefore, MSCT provides detailed information and respiratory failure, distinguishing from the more indolent and Rev. Argent. Radiol. 2019;83(3): 113-120 113 Eosinophilic Lung Diseases: Findings that a Radiologist Should Know Table 1: Summary of findings Entity Clinical presentation X-ray findings MSCT findings IELD: Nonspecific/Absent Peripheral patchy opacities GG/consolidative opacities + satellite nodules + Loeffler S. peribronchial thickening IELD: AEP Febrile S. + respiratory Bilateral GG opacities + interlobular septal thickening + pleural effusion failure of unknown etiology IELD: CEP Systemic S. + pulmonary Bilateral dense, multifocal consolidations located in the peripheral lung fields manifestations IELD: HES Dermatologic + Patchy reticular areas + poorly defined nodules with or without GG halo + pulmonary + cardiac pleural effusion (50%) SELD: 5 stages Tubular “gloved-finger” Consolidations of mucoid impaction + Aspergillosis opacity + bronchial segmental and subsegmental bronchiectasis of distribution + upper the upper lobes + centrilobular nodules and central lung fields + bronchiectasis and fibrosis VELD: CSS Small vessel vasculitis Bilateral + transient Symmetrical and peripheral consolidations + nonsegmental septal thickening + effusion (50/10% due to consolidation heart failure) + findings associated with asthma VELD: GPA Pulmonary disease + Nodules + cavitation + predilection for the lung apices + subpleural + halo sinusitis + sign + airway involvement glomerulonephritis VELD: NSG Pulmonary vasculitis Bilateral nodules + subpleural and peribronchovascular + cavitation + IVC enhancement + mediastinal lymph nodes + diffuse subpleural granulomas + fibrosis VELD: SS Dry mouth and eyes Nonspecific interstitial pneumonia + bronchi- or bronchio-lectasis + bronchial wall thickening + air cysts + thymic involvement Abbreviations: AEP, acute eosinophilic pneumonia; CEP, chronic eosinophilic pneumonia; CSS, Churg-Strauss syndrome; GG, ground glass; GPA, granulomatosis with polyangiitis; HES, hypereosinophilic syndrome; IELD, idiopathic eosinophilic lung disease; IVC, intravenous contrast; NSG, necrotizing sarcoid granulomatosis; SELD, secondary eosinophilic lung disease; SS, Sjögren syndrome; VELD, vasculitis- associated eosinophilic lung disease;. less severe presentation of chronic eosinophilic pneumonia.2,8 with no evidence of extrapulmonary involvement. BAL fluid Of unknown etiology, with a slight predominance in men, analysis shows an elevated mixed count with increased levels AEP is associated with exposure to various antigens, being of lymphocytes and eosinophils (over 25%).9 tobacco the most frequent of all.9 It presents acute febrile The most characteristic CT findings are bilateral ground-glass illness lasting 1 to 5 days, myalgia, pleuritic chest pain and re- opacities with interlobular septal thickening and pleural ef- spiratory failure manifesting as severe hypoxemia, i.e., partial fusion. Although the clinical presentation is nonspecific and pressure of oxygen in arterial blood (PaO2) below 60 mmHg, an increased eosinophil count in peripheral blood may be ab- 114 Rev. Argent. Radiol. 2019;83(3): 113-120 Juliana Couture et al. sent, the possibility of this disease should always be consid- Hypereosinophilic syndrome (HES) ered in a healthy subject who develops acute respiratory fail- The term “hypereosinophilic syndromes” (HES) refers to ure of unknown etiology and presents the above-mentioned a group of disorders characterized by elevated numbers of radiologic findings (Fig. 1).10 circulating blood eosinophils accompanied by end-organ in- filtration leading to clinical disease.8 HES is defined as the Chronic Eosinophilic Pneumonia (CEP) presence of eosinophilia greater than 1500/mm3 on two or CEP is a rare disorder characterized by systemic and pulmo- more occasions or symptoms suggestive of tissue eosinophilia nary manifestations, blood eosinophilia, peripheral opacities with blood eosinophilia and exclusion of secondary causes. on chest X-ray and a prompt response to corticosteroids.11 It The average age at HES onset is 50 years, with female pre- is more predominant in female nonsmokers, and it does not dominance.2 However, it may occur in children. Even if initial lead to severe hypoxemia or acute respiratory failure. Eosino- manifestations are dermatologic, lungs are affected in the phil count is elevated in BAL fluid. Chest X-ray shows bilateral second place (40%) and cardiac involvement is the major dense, multifocal consolidations located in the periphery of cause of morbidity and mortality.4,9 CT findings show reticu- lung fields (Fig. 2).9 lar areas of increased density with patchy distribution, poorly a b c Fig. 1 Acute eosinophilic pneumonia. Forty-nine year-old female patient with a history of cough and febrile syndrome. (A) An- teroposterior chest radiography (X-ray) shows areas of decreased transparency in the upper third of both lung fields (arrows). Axial (B) and coronal (C) chest MSCT shows multiple areas of increased attenuation of the lung parenchyma that are ground- glass in character in both upper lobes (arrows), associated with interlobular septal thickening (star) and subtle areas with a tendency to consolidation of predominantly subpleural distribution (arrowhead). Complementarily, laboratory tests revealed a white blood cell count of 15,000 cell/mm3 with 34% eosinophils. Rev. Argent. Radiol. 2019;83(3): 113-120 115 Eosinophilic Lung Diseases: Findings that a Radiologist Should Know a a b b c Figure 2 Chronic eosinophilic pneumonia. Chest MSCT in axial (A) and sagittal (B) views shows multiple areas of ground- glass decreased transparency of the lung parenchyma, involv- ing both lower lobes, predominantly the left lobe (arrow), associated with interlobular septal thickening (star), traction bronchiectasis and small subpleural cystic lesions (arrow- Figure 3 Hypereosinophilic syndrome. Axial chest MSCT (A, head), with no clear evidence of honeycombing. BAL fluid B) with zoom into the region of interest shows multiple solid analysis reveals a cytological smear with a large number of nodular/small nodular lesions in both lower lobes (circle) in bronchial cells, lymphocytes and macrophages, a finding that a patient with a clinical diagnosis of hypereosinophilic syn- is consistent with a chronic interstitial process. drome. (C) Same patient with a different intercurrent condi- tion, with pleural effusion (arrow) and focal and nodular pleu- ral thickening (arrowhead). defined nodules with or without surrounding