Acute eosinophilic pneumonia: a hypersensitivity phenomenon?

Eosinophilic interstitial lung disease

PURPOSE OF REVIEW

Although rare, the eosinophilic lung diseases are being increasingly identified as distinct clinical entities. These disorders are a heterogeneous group of disorders in which there is an increased number of eosinophils in the airways and/or lung parenchyma. These disease entities may be broadly separated into airway disorders (asthma, allergic bronchopulmonary mycosis, eosinophilic bronchitis, and bronchocentric granulomatosis) and parenchymal (interstitial) disorders. This review and update will concentrate on the latter group of entities.

RECENT FINDINGS

Recent publications in the field have concentrated on expanding the list of causative agents and clinical situations. An especially promising number of articles report advancements in the understanding of the pathogenetic mechanisms behind the development of the clinical syndromes.

SUMMARY

Whatever the function of the eosinophil in these disorders, it is important to remember that the disease processes lumped together as the eosinophilic lung diseases are a heterogeneous group of diseases. In an attempt to categorize these disorders, they have been connected, either appropriately or artificially, by their association with the eosinophil. Nevertheless, the eosinophilic connection may serve as a clue to pathogenesis and treatment.

Clinicopathological differences between acute and chronic eosinophilic pneumonia

OBJECTIVE

Considerable confusion exists regarding the proper classification of idiopathic eosinophilic pneumonia (IEP). Furthermore, there are no reports describing the clinicopathological differences between the various forms of eosinophilic pneumonias.

METHODOLOGY

The histological findings in acute eosinophilic pneumonia (AEP) and chronic eosinophilic pneumonia (CEP) were examined and the clinical and radiological features were contrasted with them.

RESULTS

Radiologically, ground glass opacity and interlobular septal thickening were characteristic of the AEP cases, while air space consolidation was seen in all CEP cases. Histologically, interstitial oedema and fibrin deposition were prominent in the AEP cases. Type II cells were detached from the alveolar walls, although the basal lamina was predominantly intact. In CEP, in addition to cellular infiltration, there was prominent intraluminal fibrosis. Disruption of the basal lamina was observed and nests of intraluminal fibrosis were directly adjacent and connected to the alveolar walls.

CONCLUSIONS

An essential histological difference between AEP and CEP is the severity of basal lamina damage and the amount of subsequent intraluminal fibrosis. In AEP particularly, these findings explain the radiographical findings, as well as the rapid and complete improvement noted in such cases.

Eosinophilic lung diseases

In the last 30 years studies have shown that the lungs have been the target of eosinophilic migration producing eosinophilic lung diseases (ELD) secondary to allergens, irritants, parasites, infections, antibodies and drugs. Specific diagnoses can be made by: (1) Peripheral blood eosinophilia and chest X-ray infiltrates. (2) Lung biopsy. (3) Bronchoalveolar lavage (BAL). In developing countries ELD are most frequently associated with parasitic infection. This paper defines, classifies and presents the clinical characteristics and treatment of these diseases with emphasis on parasitic lung problems.

Idiopathic acute eosinophilic pneumonia: a study of 22 patients

Idiopathic acute eosinophilic pneumonia (IAEP) is characterized by acute febrile respiratory failure associated with diffuse radiographic infiltrates and pulmonary eosinophilia. We conducted a multicenter retrospective study to characterize this rare clinical entity further and to improve its diagnostic criteria. A total of 13 male and 9 female patients (mean age: 29 +/- 15.8 years) presented with severe hypoxemia (Pa(O2)/fraction of inspired oxygen ratio = 156 +/- 74.1) requiring mechanical ventilation in 14 cases. Bronchoalveolar lavage was performed on all patients and showed 54.4 +/- 19.2% eosinophils on differential cell count, but no open-lung biopsies were done. No clinical differences were found between patients seen at less than 7 days (n = 15) or at 7 to 31 days (n = 7) from the onset of IAEP. A total of 12 patients met the clinical criteria of acute lung injury, and eight of these patients met the criteria for acute respiratory distress syndrome. All patients recovered, either spontaneously (6) or on corticosteroid treatment (16). No relapses occurred. We conclude that: (1) diagnostic criteria of IAEP are compatible with a duration of symptoms for up to 1 month, but the response to corticosteroid treatment is not diagnostic because of possible spontaneous recovery; (2) IAEP should be considered as differential diagnosis of acute lung injury or acute respiratory distress syndrome; (3) bronchoalveolar lavage eosinophilia obviates the need for lung biopsy in IAEP.

Acute eosinophilic pneumonia in a New York City firefighter exposed to World Trade Center dust

We report a sentinel case of acute eosinophilic pneumonia in a firefighter exposed to high concentrations of World Trade Center dust during the rescue effort from September 11 to 24. The firefighter presented with a Pa(O2) of 53 mm Hg and responded to oxygen and corticosteroids. Computed tomography scan showed patchy ground glass density, thickened bronchial walls, and bilateral pleural effusions. Bronchoalveolar lavage recovered 70% eosinophils, with only 1% eosinophils in peripheral blood. Eosinophils were not degranulated and increased levels of interleukin-5 were measured in bronchoalveolar lavage and serum. Mineralogic analysis counted 305 commercial asbestos fibers/10(6) macrophages including those with high aspect ratios, and significant quantities of fly ash and degraded fibrous glass. Acute eosinophilic pneumonia is a rare consequence of acute high dust exposure. World Trade Center dust consists of large particle-size silicates, but fly ash and asbestos fibers may be found in bronchoalveolar lavage cells.

Eosinophilic lung disease in the tropics

Paul Ehrlich first described the eosinophil in 1879. It is a pro-inflammatory cell that is involved in the immune defense against various offenders in atopic and nonatopic individuals. Eosinophils derive from an unknown progenitor cell in the bone marrow. This article reviews the etiology and effects of this condition.

Elevated levels of thymus- and activation-regulated chemokine in bronchoalveolar lavage fluid from patients with eosinophilic pneumonia

Thymus- and activation-regulated chemokine (TARC/CCL17) is a lymphocyte-directed CC chemokine, which plays a role in the recruitment of CC chemokine receptor-4 positive T helper 2 (Th2) cells. In this study, we measured concentrations of TARC and Th2 cell-derived cytokines in bronchoalveolar lavage (BAL) fluid, as well as TARC concentrations in serum from patients with eosinophilic pneumonia and other interstitial lung diseases. TARC was significantly elevated in BAL fluids from patients with eosinophilic pneumonia (median, 240 pg/ml), whereas TARC was undetectable (< 7 pg/ml) in most cases of hypersensitivity pneumonitis, sarcoidosis, and idiopathic pulmonary fibrosis, as well as in healthy control subjects. Also, when present, quantities were less than 20 pg/ml. Elevated concentrations of interleukin (IL)-4, IL-5, and IL-13 were also detected in BAL fluid from patients with eosinophilic pneumonia. Interestingly, TARC concentrations in BAL fluids were closely correlated with the concentrations of IL-5 and IL-13. A serial examination showed that elevated TARC in BAL fluid rapidly fell to below detectable limits preceding decreases in IL-5 concentration and eosinophil percentage. Our results, in concordance with previous studies, demonstrate the potential activity of TARC for recruiting Th2 cells to the lungs and suggest a significant role for TARC in the pathogenesis of eosinophilic pneumonia.

Acute eosinophilic pneumonia in AIDS

A 39-year-old man with AIDS presented with acute respiratory distress and diffuse bilateral infiltrates seen on a chest radiograph. Acute eosinophilic pneumonia (AEP) was diagnosed by thoracoscopic lung biopsy. There was no evidence of an infectious etiology, and the patient rapidly improved with corticosteroid therapy. Several of the idiopathic interstitial pneumonias have been reported in adult patients with AIDS. To our knowledge, this case represents the first tissue-confirmed case of AEP associated with adult AIDS.

Pulmonary infiltrates with eosinophilia syndromes in children

Pulmonary infiltrates with eosinophilia (PIE) are a group of heterogeneous disorders having the common findings of lung disease and eosinophilia in the peripheral blood, bronchoalveolar lavage fluid, or pulmonary interstitium. Eleven cases of PIE syndromes were identified through a retrospective and prospective chart review: drug-induced (2), acute eosinophilic pneumonia (3), infant pulmonary eosinophilia (2), parasite-induced (2), Churg-Strauss syndrome (1), and atypical chronic PIE (1). Patient demographics, clinical presentation, and disease severity varied considerably among groups. Therapeutic interventions included bronchodilators (10), oxygen (7), corticosteroids (9), and mechanical ventilation (3). A single patient with acute eosinophilic pneumonia died. Our experience suggests that PIE syndromes are rare in childhood and that clinical presentation can vary widely. Because of the potential for significant morbidity and mortality, aggressive diagnostic evaluations are warranted, particularly in children with respiratory failure of unknown etiology.

Steroid-refractory neonatal eosinophilic pneumonia responsive to cyclosporin A

Idiopathic neonatal eosinophilic pneumonia is extremely rare. We report an infant who presented with tachypnea and interstitial infiltrates on chest radiograph at age 2 wk. Lung biopsy revealed perivascular and interstitial eosinophils. Despite initial improvement, the patient's condition became resistant to corticosteroids, cromolyn, and intravenous gamma globulin. After treatment with cyclosporin A his symptoms resolved.

Acute eosinophilic pneumonia associated with shock

OBJECTIVE

To describe an unusual case of acute eosinophilic pneumonia (AEP) associated with hemodynamic instability.

DESIGN

Case report, clinical.

SETTINGS

Tertiary care intensive care unit (ICU).

PATIENT

A single patient admitted to the ICU.

INTERVENTIONS

Intravenous corticosteroids.

MEASUREMENTS AND MAIN RESULTS

Resolution of distributive shock and respiratory failure.

CONCLUSIONS

AEP with respiratory failure was first reported in 1989 as a distinct clinical entity. Patients with this variant of eosinophilic lung disease develop acute hypoxemic respiratory failure with a rapid response to treatment with corticosteroids, The characteristic feature of this syndrome is a predominance of eosinophils found in bronchoalveolar lavage fluid and lung biopsy. Despite the increasing number of reported cases, to our knowledge, distributive shock has not been reported as a feature of AEP. We report a unique case of AEP associated with shock and review the pertinent literature.

Nonresolving or slowly resolving pneumonia

Given the variability in rate of radiographic resolution, it remains controversial to decide when to initiate an invasive diagnostic work-up for nonresolving or slowly resolving pulmonary infiltrates. In immunocompetent patients who present with classical features of CAP (i.e., fever, chills, productive cough, new pulmonary infiltrate), clinical response to therapy is the most important determinant for further diagnostic studies. Within the first few days, persistence or even progression of infiltrates on chest radiographs is not unusual. Defervescence, diminished symptoms, and resolution of leukocytosis strongly support a response to antibiotic therapy, even when chest radiographic abnormalities persist. In this context, observation alone is reasonable, and invasive procedures can be deferred. Serial radiographs and clinical examinations dictate subsequent evaluation. In contrast, when clinical improvement has not occurred and chest radiographs are unchanged or worse, a more aggressive approach is warranted. In this setting, we advise fiberoptic bronchoscopy with BAL and appropriate cultures for bacteria, legionella, fungi, and mycobacteria. When endobronchial anatomy is normal and there is no purulence to suggest infection, TBBs should be done to exclude noninfectious causes (discussed earlier) or infections attributable to mycobacteria or fungi. An aggressive approach is also warranted in patients who are clinically stable or improving when the rate of radiographic resolution is delayed. As discussed earlier, what constitutes excessive delay is controversial, and depends upon the acuity of illness, specific pathogen, extent of involvement (i.e., lobar versus multilobar), comorbidities, and diverse host factors. Stable infiltrates even 2 to 4 weeks after institution of antibiotic therapy does not mandate intervention provided patients are improving clinically. Invasive techniques can also be deferred when unequivocal, albeit incomplete, radiographic resolution can be demonstrated. Lack of at least partial radiographic resolution by 6 weeks, even in asymptomatic patients, however, deserves consideration of alternative causes (e.g., endobronchial obstructing lesions, or noninfectious causes). Fiberoptic bronchoscopy with BAL and TBBs has minimal morbidity and is the preferred initial invasive procedure for detecting endobronchial lesions or substantiating noninfectious causes. The yield of bronchoscopy depends on demographics, radiographic features, and pre-test likelihood. In the absence of specific risk factors, the incidence of obstructing lesions (e.g., bronchogenic carcinomas, bronchial adenomas, obstructive foreign body) is low. Bronchogenic carcinoma is rare in nonsmoking, young (< 50 years) patients but is a legitimate consideration in older patients with a history of tobacco abuse. Non-neoplastic causes (e.g., pulmonary vasculitis, hypersensitivity pneumonia, etc.) should be considered when specific features are present (e.g., hematuria, appropriate epidemiologic exposures). Ancillary serologic tests or biopsies of extrapulmonary sites are invaluable in some cases. In rare instances, surgical (open or VATS) biopsy is necessary to diagnose refractory or non-resolving "pneumonias."

Idiopathic chronic eosinophilic pneumonia. A clinical and follow-up study of 62 cases. The Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P)

Idiopathic chronic eosinophilic pneumonia (CEP) is a rare disorder of unknown cause with nonspecific respiratory and systemic symptoms but rather characteristic peripheral alveolar infiltrates on imaging, developing mainly in women and in atopic subjects. The disorder is highly responsive to oral corticosteroid therapy, but relapses are frequent on reducing or stopping treatment. The long-term course of the disease and data regarding outcome, particularly the need for prolonged oral corticosteroid therapy and the development of severe asthma, are somewhat contradictory. A multicentric retrospective study was conducted in an attempt to describe better the initial features and, above all, the later course of CEP in a large homogeneous series of 62 stringently selected patients of whom 46 were followed for more than 1 year. The prevalence of smokers was low (6.5%) and about half of our patients (51.6%) had a previous, and often prolonged, history of asthma. The clinical and roentgenographic features were in keeping with previous studies, but we found that computed tomography could disclose ground glass opacities not detected by X-ray, and that migratory infiltrates before treatment were more frequent (25.5%) than reported previously. The bronchoalveolar lavage cellular count always showed a striking eosinophilic pattern, thus allowing distinction between CEP and cryptogenic organizing pneumonia, both syndromes sharing many common clinical and imaging features. About two-thirds of the patients (68%) showed a ventilatory defect in pulmonary function tests, with about one-half of these presenting with an obstructive pattern, sometimes without previous asthma. Along with the submucosal eosinophilic infiltration noted in 2 patients without ventilatory defect, this is strong evidence to confirm that CEP is not only an alveolointerstitial but also an airway disease. The dramatic response to oral corticosteroid therapy was observed in all treated patients. Although only 1 patient initially treated for less than 6 months did not relapse, longer oral corticosteroid therapy in no way provided protection from further relapses. We thus propose to try to wean oral corticosteroid therapy after 6 months in patients without severe asthma, because recurrences remain responsive to oral steroids. However, prolonged oral corticosteroid therapy was necessary in the majority of patients, with 68.9% of those followed for more than 1 year still on oral corticosteroid therapy at the last follow-up, either because of relapse or because of severe asthma.

Acute eosinophilic pneumonia: a cause of reversible, severe, noninfectious respiratory failure

We report a case of acute eosinophilic pneumonia associated with adult respiratory distress syndrome in an adolescent. This entity should be considered in the differential diagnosis in previously well children and adolescents who are seen with unexplained respiratory failure and who have many eosinophils in bronchoalveolar lavage fluid. Prompt recognition of this rapidly reversible noninfectious disorder and institution of corticosteroids may be lifesaving.

The spectrum of eosinophilic lung disease: radiologic findings

PURPOSE

Eosinophilic lung disease includes various disease entities. Each disease manifests different radiologic findings. The purpose of this review is to present the radiologic findings of the spectrum of eosinophilic lung disease.

METHOD

We reviewed the radiologic, histologic, and clinical findings of the spectrum of eosinophilic lung disease from the previous reports and our experiences.

RESULTS

Simple pulmonary eosinophilia is characterized by transient and migrating opacities on chest radiography. Acute eosinophilic pneumonia is characterized by acute clinical symptoms and signs and rapid changes of radiographic diffuse reticular lesions. Chronic eosinophilic pneumonia, with more prolonged symptom duration, history of asthma, occurrence of relapse, and radiologic features of subpleural consolidation, can be differentiated from acute eosinophilic pneumonia. Allergic bronchopulmonary aspergillosis presents with bilateral central bronchiectasis with or without mucoid impaction. Although these diseases show specific radiographic findings, some show overlapping radiographic features. High-resolution CT enables characterization of parenchymal lesions further by showing internal and marginal features and the exact extent of the lesions. Extrapulmonary organs are involved in Churg-Strauss syndrome and idiopathic hypereosinophilic syndrome. Asthma is associated with Churg-Strauss syndrome, allergic bronchopulmonary aspergillosis, chronic eosinophilic pneumonia, and bronchocentric granulomatosis.

CONCLUSION

Integration of clinical, laboratory, and radiologic findings enables initial and differential diagnoses of various eosinophilic lung diseases.

A case of acute eosinophilic pneumonia. Evidence for hypersensitivity-like pulmonary reaction

We examined an 86-year-old man with acute respiratory failure. A chest roentgenogram showed diffuse reticular shadows. Transbronchial biopsy revealed thickening of the alveolar septa accompanied by moderate eosinophil infiltration. After admission to the hospital, the patient's symptoms immediately improved without any medication. Clinical course and pathologic findings suggested acute eosinophilic pneumonia caused by a hypersensitivity reaction.

Acute eosinophilic pneumonia. A summary of 15 cases and review of the literature

Idiopathic acute eosinophilic pneumonia (AEP) is an acute febrile illness that may be mistaken for an infectious pneumonia. Patients are often young and otherwise healthy. Clues to considering this disorder in a differential diagnosis include the acuity and severity of the clinical presentation and an initial chest X-ray with diffuse infiltrates, often interstitial, and the presence of Kerley B lines and/or evidence of pleural fluid. The diagnosis can be made through examination of bronchoalveolar lavage fluid in most cases, with careful exclusion of other similar eosinophilic lung disease. Although it can lead to life-threatening respiratory failure, AEP is easily treatable with corticosteroids. This disease has not been reported to recur in any patients to this point.

Possible involvement of an environmental agent in the development of acute eosinophilic pneumonia

BACKGROUND

Although the pathogenesis of acute eosinophilic pneumonia remains largely unknown, it has been suggested that it may include a hypersensitivity phenomenon induced by inhaled environmental antigens.

METHODS

To investigate this possibility, we studied the effect of environmental challenges in three patients with acute eosinophilic pneumonia. Symptoms and laboratory findings were evaluated before and after the challenge tests in the patient's homes and their places of work.

RESULTS

After the provocation challenges to their homes, all three patients developed fever, cough, and fatigue and two of them presented with dyspnea. Inspiratory crackles became audible in all cases, and there was a decreased Pao2 level in two. Similar challenges at their workplaces were negative. After moving out of their homes, the patients engaged in their usual work but had no recurrent episodes.

CONCLUSIONS

These results suggest that environmental factors in the home can be the cause of acute eosinophilic pneumonia. In order to elucidate the pathogenesis of the disease, it is important to further investigate environmental factors.

Acute eosinophilic pneumonia in a patient infected with the human immunodeficiency virus

A 24-year-old man infected with the human immunodeficiency virus (HIV) developed cough and progressive dyspnea over a period of 4 weeks. Absolute blood eosinophil count was 3360/mm3. Chest X-ray revealed alveolointerstitial infiltrates in both lower lobes. Eosinophilia was also found in bronchoalveolar lavage fluid. The clinical picture improved dramatically with steroids. Other causes of acute eosinophilic pneumonia were excluded.

The approach to nonresolving pneumonia

Pneumonias that fail to resolve at the expected rate may reflect derangements in host defenses, inadequate or inappropriate antimicrobial therapy, highly virulent pathogens, or myriad noninfectious causes. In this article, noninfectious causes of pulmonary infiltrates mimicking community-acquired pneumonia are discussed. The salient clinical, radiographic, and histopathologic features of diverse immune-mediated syndromes are reviewed, and an approach to diagnosis and therapy of nonresolving pneumonias is presented.

A clinical study of idiopathic eosinophilic pneumonia

To better characterize idiopathic eosinophilic pneumonia (IEP), we studied the clinical and laboratory features of 27 patients. Patients with IEP could be divided into those with chronic eosinophilic pneumonia (CEP) (n = 14) and acute eosinophilic pneumonia (AEP) (n = 13). CEP was characterized by (1) multiple and dense areas of consolidation on chest radiographs and computed tomographic (CT) scans, (2) persistent symptoms, (3) a requirement for steroid therapy, and (4) possible relapses. On the other hand, AEP was characterized by (1) diffuse ground-glass and micronodular infiltrates on radiographs and CT scans (in mild cases, the lesions were sparse or localized), (2) acute onset with high fever, (3) spontaneous improvement, and (4) no relapse. In addition, peripheral blood eosinophil count was significantly higher in patients with CEP than in patients with AEP at the first examination. However, the eosinophil fraction also became markedly elevated during the subsequent courses of AEP. Analysis of bronchoalveolar lavage fluid revealed that the percentage of eosinophils was higher in patients with CEP than that in patients with AEP, whereas the percentage of lymphocytes was significantly greater in patients with AEP than patients with CEP. It was also noted that 75 percent of patients with CEP and 82 percent of patients with AEP had allergic diathesis, suggesting that both conditions are likely to occur in atopic individuals.

Sephadex-induced granulomatous alveolitis in rat: effects of antigen manipulation

A granulomatous alveolitis, with multinuclear cell formation combined with an eosinophilic peribronchiolitis, was achieved in rats by intratracheal administration of sephadex beads (G-200, Pharmacia, Sweden). The pattern of inflammation and the degree of postgranulomatous fibrosis were substantially dampened when the particles were dispersed by ultrasonification. The animals were analyzed with bronchoalveolar lavage and tissue morphology.

Transient wheeze. Eosinophilic bronchobronchiolitis in acute eosinophilic pneumonia

The clinicopathologic features of five patients with acute eosinophilic pneumonia who presented with transient wheeze as well as acute onset of high fever, severe hypoxemia, and diffuse pulmonary infiltrates are described. Eosinophilic pneumonia was diagnosed by bronchoalveolar lavage and transbronchial lung biopsy. The illness resolved rapidly with or without corticosteroid therapy. No relapse occurred. To characterize the transient wheeze, a transbronchoscopic bronchial biopsy and pulmonary function tests were performed. Specimens of bronchial wall revealed eosinophil infiltration into the bronchial mucosa. Pulmonary function tests demonstrated reduced diffusing capacity and small airway dysfunction. These findings suggested that eosinophil infiltration into the bronchial mucosa might temporarily cause transient wheeze, different from bronchial asthma, due to small airway dysfunction in acute eosinophilic pneumonia.

Acute eosinophilic pneumonia due to toxocariasis with bronchoalveolar lavage findings

A previously healthy young man presented with breathlessness, diffuse pulmonary infiltrates on the chest x-ray film, and a high degree of peripheral blood eosinophilia. Analysis of bronchoalveolar lavage (BAL) fluid showed 64 percent eosinophils. A diagnosis of toxocariasis was eventually reached on the basis of a positive enzyme-linked immunosorbent assay (ELISA) for Toxocara canis. The routine performance of the ELISA test for Toxocara in the diagnostic approach to pulmonary infiltration with eosinophilia could reveal an undetermined, sometimes unsuspected, number of cases of adult toxocariasis with pulmonary involvement. A high degree of eosinophilia in the differential cell count of BAL fluid may eventually prove to be a useful clue in favor of such a diagnosis.

Cocaine induced eosinophilic lung disease

A patient developed fever, bronchoconstriction, hypoxaemia, pulmonary infiltrates, and serum and bronchoalveolar lavage fluid eosinophilia on two occasions after inhaling crack cocaine. Transbronchial biopsy specimens showed normal lung parenchyma but a dense eosinophilic infiltrate within the bronchial wall. Both episodes resolved promptly after treatment with corticosteroids. Eosinophilic lung disease may be a steroid responsive complication of crack cocaine abuse.

Acute eosinophilic pneumonia with respiratory failure: a new syndrome?

Acute, noninfectious, eosinophilic pneumonia with respiratory failure has been described in adults. This new form of eosinophilic lung disease differs from the previously described types of eosinophilic pneumonia. Patients with this entity develop rapid progressive respiratory failure, which seems to respond to corticosteroid therapy. Eosinophilia in lung biopsy specimen, or in bronchoalveolar lavage fluid seems to be a common denominator. We present the first pediatric case of this new, distinct form of eosinophilic lung disease and review the pertinent literature.

Fatal pulmonary aspergillosis presenting as acute eosinophilic pneumonia in a previously healthy child

A previously healthy boy presented with cough and diffuse pulmonary interstitial infiltrates. Acute eosinophilic pneumonia was diagnosed by bronchoalveolar lavage in the absence of a demonstrable infectious etiologic agent. Corticosteroid therapy resulted in immediate improvement but was followed by respiratory distress and death from invasive aspergillosis and Pseudomonas cepacia sepsis.

Hypersensitivity pneumonitis versus invasive pulmonary aspergillosis: two cases with unusual pathologic findings and review of the literature

Two brothers simultaneously exposed to moldy hay, who developed differing forms of Aspergillus-related lung disease, are presented. Patient 1 developed a true case of hypersensitivity lung disease, whereas his brother developed invasive aspergillosis with bronchoalveolar lavage eosinophilia and unusual pathologic features including tissue eosinophilia. The possible overlap between hypersensitivity pneumonitis and invasive aspergillosis in the immunocompetent host is discussed.

Aerosol therapy in AIDS

Pneumocystis carinii pneumonia (PCP) is the most common presenting symptom in patients with the acquired immunodeficiency syndrome (AIDS). Clinical trials have shown that inhaled pentamidine, delivered by nebulizer, is an effective prophylaxis for PCP in high-risk patients, and can be used to treat mild to moderate episodes. Side effects are minor, in marked contrast to the parenteral route of administration. The choice of nebulizer system will determine both alveolar delivery of pentamidine and the incidence of cough related to deposition of droplets on large conducting airways. Radioaerosol studies have suggested that optimum nebulizer systems for inhaled pentamidine deliver the majority of the aerosol mass in droplets smaller than 2 microns diameter, ideal for alveolar penetration.

Diagnostic significance of increased bronchoalveolar lavage fluid eosinophils

We determined the incidence of increased bronchoalveolar lavage (BAL) fluid eosinophil percentages in 1,059 consecutive patients undergoing bronchoscopy with BAL over a 33-month period. Forty-eight (48) patients were found to have 5% or more BAL eosinophils. The most common causes for increased BAL eosinophils were interstitial lung diseases (40% of patients), acquired immunodeficiency syndrome (AIDS)-associated pneumonia (17% of patients), idiopathic eosinophilic pneumonia (15% of patients), and drug-induced lung disease (12% of patients). Together, these four diagnoses accounted for 84% of all patients. In contrast, eosinophils were uncommon in the BAL of patients with the adult respiratory distress syndrome, lung cancer, community-acquired pneumonia, or immunocompromising diseases other than AIDS. The finding of increased BAL eosinophils was most helpful in patients presenting with unexplained pulmonary infiltrates. In these patients, this finding was often an important clue to the final diagnosis. We conclude that although the finding of an increased percentage of BAL eosinophils is uncommon, when present it is relatively specific for a limited number of diseases.

Pulmonary vascular damage and the development of cor pulmonale following hyaline membrane disease

Light microscopic morphometric techniques have been used to study the lungs in 17 infants and young children aged 2 weeks to 3.5 years who were born prematurely, developed hyaline membrane disease (HMD), and died with chronic lung disease. They were divided into three groups. In group 1 the babies died without recovering from their initial illness at age 2-13 weeks. In group 2 they died, aged 4-15 months, having recovered from the neonatal illness. Neither group showed clinical or pathological evidence of cor pulmonale (CP). In group 3 children died aged 6 months to 3.5 years with CP. None of the 17 patients had classical fibrotic bronchopulmonary dysplasia (BPD) but all had a reduced alveolar number and an increase in bronchial smooth muscle in small airways. All three groups showed an increase in pulmonary arterial medial thickness (P less than 0.001). In group 1 the appearance of the arteries suggested persistance of the fetal state. In group 2 and 3 the vessels had a more mature structure; in group 3 a marked secondary increase in muscularity was found, approaching the thickness seen in fetal life. In groups 2 and 3 muscle extended into smaller arteries than normal. Vein wall thickness was increased. The alveolar to arterial ratio was normal, the alveolar number was reduced, therefore the total number of arteries was reduced in all three groups. Thus, babies who recover from HMD may have significant vascular abnormalities in the absence of CP; conversely, CP if present, does not mean advanced obliterative pulmonary vascular disease. Thus, pulmonary vascular morphology does not correlate with the presence or absence of CP.