exposure, but recur after the next antigen contact. Tachypnea and diffuse Þne crackles are observed on physical examination.

accompanied by interlobular septal thickening and sometimes by consolidation or poorly deÞned small nodules [36, 41] (Figs. 21.7 and 21.8).

The most common HRCT Þndings of acute HP consist of diffuse GGO and consolidation [38]. Centrilobular nodules also may be seen (Fig. 21.6).

Bilateral areas of GGO on HRCT correspond histopathologically to diffuse alveolar damage associated with interstitial and alveolar eosinophilia [42].

Diffuse GGO and consolidation may be due to cellular interstitial pneumonia or acute organizing pneumonia [27, 37].

Patient Prognosis

Early diagnosis and avoidance of antigen exposure are crucial in the management. Corticosteroids are recommended in severe respiratory impairment with hypoxemia. If the diagnosis is correctly and timely done, outcome is usually good.

Acute Eosinophilic Pneumonia

Pathology and Pathogenesis

AEP shows the features of diffuse alveolar damage in its exudative or organizing phases, coupled with a heavy interstitial inÞltrate. In its exudative phase, diffuse alveolar damage is characterized by hyaline membranes and in its organizing phase by interstitial Þbroblast proliferation, prominent alveolar epithelial regeneration, and organizing alveolar exudates [39].

Symptoms and Signs

Patients present with rapid onset of cough, tachypnea, and dyspnea of usually less than 7 days duration. Patients can progress from mild dyspnea to life-threatening respiratory failure in only a few hours. Fever is invariably present. Pleuritic chest pain and myalgia are common. Crackles are present in 80 % of patients. The disease is frequently misdiagnosed as severe community-acquired pneumonia [40].

CT Findings

The predominant patterns of parenchymal abnormality seen at HRCT are bilateral patchy areas of GGO, frequently

Approximately two-thirds of patients require mechanical ventilation, but they respond rapidly and completely to corticosteroids. Most patients have complete recovery with no long-term pulmonary symptoms [43].

References

1.Mueller-Mang C, Grosse C, Schmid K, Stiebellehner L, Bankier AA. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics. 2007;27:595Ð615.

2.Lee KS, Kullnig P, Hartman TE, Muller NL. Cryptogenic organizing pneumonia: CT Þndings in 43 patients. AJR Am J Roentgenol. 1994;162:543Ð6.

3. Kim Y, Lee KS, Choi DC, Primack SL, Im JG. The spectrum of eosinophilic lung disease: radiologic Þndings. J Comput Assist Tomogr. 1997;21:920Ð30.

4. Min JH, Lee HY, Lim H, et al. Drug-induced interstitial lung disease in tyrosine kinase inhibitor therapy for non-small cell lung cancer: a review on current insight. Cancer Chemother Pharmacol. 2011;68:1099Ð109.

5. Kim EA, Lee KS, Johkoh T, et al. Interstitial lung diseases associated with collagen vascular diseases: radiologic and histopathologic Þndings. Radiographics. 2002;22 Spec No:S151Ð65.

6.Katzenstein AL, Fiorelli RF. NonspeciÞc interstitial pneumonia/ Þbrosis. Histologic features and clinical signiÞcance. Am J Surg Pathol. 1994;18:136Ð47.

7. Travis WD, Hunninghake G, King Jr TE, et al. Idiopathic nonspeciÞc interstitial pneumonia: report of an American Thoracic Society Project. Am J Respir Crit Care Med. 2008;177:1338Ð47.

8. Kligerman SJ, Groshong S, Brown KK, Lynch DA. NonspeciÞc interstitial pneumonia: radiologic, clinical, and pathologic considerations. Radiographics. 2009;29:73Ð87.

9. Park IN, Kim DS, Shim TS, et al. Acute exacerbation of interstitial pneumonia other than idiopathic pulmonary Þbrosis. Chest. 2007;132:214Ð20.

10.Tsubamoto M, Muller NL, Johkoh T, et al. Pathologic subgroups of nonspeciÞc interstitial pneumonia: differential diagnosis from other idiopathic interstitial pneumonias on high-resolution computed tomography. J Comput Assist Tomogr. 2005;29:793Ð800.

11.Kim TS, Lee KS, Chung MP, et al. NonspeciÞc interstitial pneumonia with Þbrosis: high-resolution CT and pathologic Þndings. AJR Am J Roentgenol. 1998;171:1645Ð50.

12.Yousem SA, Colby TV, Gaensler EA. Respiratory bronchiolitisassociated interstitial lung disease and its relationship to desquamative interstitial pneumonia. Mayo Clin Proc. 1989;64:1373Ð80.

13.Vassallo R. Diffuse lung diseases in cigarette smokers. Semin Respir Crit Care Med. 2012;33:533Ð42.

14.Hartman TE, Primack SL, Swensen SJ, Hansell D, McGuinness G, Muller NL. Desquamative interstitial pneumonia: thin-section CT Þndings in 22 patients. Radiology. 1993;187:787Ð90.

15.Hidalgo A, Franquet T, Gimenez A, Bordes R, Pineda R, Madrid M. Smoking-related interstitial lung diseases: radiologic-patho- logic correlation. Eur Radiol. 2006;16:2463Ð70.

16.Okada F, Ando Y, Yoshitake S, et al. Clinical/pathologic correlations in 553 patients with primary centrilobular Þndings on highresolution CT scan of the thorax. Chest. 2007;132:1939Ð48.

17.Hansell DM, Wells AU, Padley SP, Muller NL. Hypersensitivity pneumonitis: correlation of individual CT patterns with functional abnormalities. Radiology. 1996;199:123Ð8.

18.Moon JH, Kim EA, Lee KS, Kim TS, Jung KJ, Song JH. Cytomegalovirus pneumonia: high-resolution CT Þndings in ten nonAIDS immunocompromised patients. Korean J Radiol. 2000;1:73Ð8.

19.Franquet T, Lee KS, Muller NL. Thin-section CT Þndings in 32 immunocompromised patients with cytomegalovirus pneumonia who do not have AIDS. AJR Am J Roentgenol. 2003;181:1059Ð63.

20.Chung MP, Yi CA, Lee HY, Han J, Lee KS. Imaging of pulmonary vasculitis. Radiology. 2010;255:322Ð41.

21.Morell F, Roger A, Reyes L, Cruz MJ, Murio C, Munoz X. Bird fancierÕs lung: a series of 86 patients. Medicine (Baltimore). 2008;87:110Ð30.

22.Lara AR, Schwarz MI. Diffuse alveolar hemorrhage. Chest. 2010;137:1164Ð71.

23.Selman M, Pardo A, King Jr TE. Hypersensitivity pneumonitis: insights in diagnosis and pathobiology. Am J Respir Crit Care Med. 2012;186:314Ð24.

24.Selman M, Buendia-Roldan I. Immunopathology, diagnosis, and management of hypersensitivity pneumonitis. Semin Respir Crit Care Med. 2012;33:543Ð54.

25.Small JH, Flower CD, Traill ZC, Gleeson FV. Air-trapping in extrinsic allergic alveolitis on computed tomography. Clin Radiol. 1996;51:684Ð8.

26. Franquet T, Hansell DM, Senbanjo T, Remy-Jardin M, Muller NL. Lung cysts in subacute hypersensitivity pneumonitis. J Comput Assist Tomogr. 2003;27:475Ð8.

27.Silva CI, Churg A, Muller NL. Hypersensitivity pneumonitis: spectrum of high-resolution CT and pathologic Þndings. AJR Am J Roentgenol. 2007;188:334Ð44.

28.Wallace JM, Hannah J. Cytomegalovirus pneumonitis in patients with AIDS. Findings in an autopsy series. Chest. 1987;92:198Ð203.

29. de Maar EF, Verschuuren EA, Harmsen MC, The TH, van Son WJ. Pulmonary involvement during cytomegalovirus infection in immunosuppressed patients. Transpl Infect Dis. 2003;5: 112Ð20.

30. Lombard CM, Colby TV, Elliott CG. Surgical pathology of the lung in anti-basement membrane antibody-associated GoodpastureÕs syndrome. Hum Pathol. 1989;20:445Ð51.

31.Primack SL, Miller RR, Muller NL. Diffuse pulmonary hemorrhage: clinical, pathologic, and imaging features. AJR Am J Roentgenol. 1995;164:295Ð300.

32.Cheah FK, Sheppard MN, Hansell DM. Computed tomography of diffuse pulmonary haemorrhage with pathological correlation. Clin Radiol. 1993;48:89Ð93.

33.Blatman KH, Grammer LC. Chapter 19: Hypersensitivity pneumonitis. Allergy Asthma Proc. 2012;33 Suppl 1:S64Ð6.

34.Catherinot E, Lanternier F, Bougnoux ME, Lecuit M, Couderc LJ, Lortholary O. Pneumocystis jirovecii pneumonia. Infect Dis Clin North Am. 2010;24:107Ð38.

35.Allen JN, Pacht ER, Gadek JE, Davis WB. Acute eosinophilic pneumonia as a reversible cause of noninfectious respiratory failure. N Engl J Med. 1989;321:569Ð74.

36.Cheon JE, Lee KS, Jung GS, Chung MH, Cho YD. Acute eosinophilic pneumonia: radiographic and CT Þndings in six patients. AJR Am J Roentgenol. 1996;167:1195Ð9.

37. Lacasse Y, Girard M, Cormier Y. Recent advances in hypersensitivity pneumonitis. Chest. 2012;142:208Ð17.

38.Silver SF, Muller NL, Miller RR, Lefcoe MS. Hypersensitivity pneumonitis: evaluation with CT. Radiology. 1989;173:441Ð5.

39.Tazelaar HD, Linz LJ, Colby TV, Myers JL, Limper AH. Acute eosinophilic pneumonia: histopathologic Þndings in nine patients. Am J Respir Crit Care Med. 1997;155:296Ð302.

40.Rhee CK, Min KH, Yim NY, et al. Clinical characteristics and corticosteroid treatment of acute eosinophilic pneumonia. Eur Respir J. 2013;41:402Ð9.

41.King MA, Pope-Harman AL, Allen JN, Christoforidis GA, Christoforidis AJ. Acute eosinophilic pneumonia: radiologic and clinical features. Radiology. 1997;203:715Ð9.

42.Jeong YJ, Kim KI, Seo IJ, et al. Eosinophilic lung diseases: a clinical, radiologic, and pathologic overview. Radiographics. 2007;27:617Ð37; discussion 637Ð9.

43.Allen J. Acute eosinophilic pneumonia. Semin Respir Crit Care Med. 2006;27:142Ð7.