SESSION TYPE: ILD Cases I
PRESENTED ON: Monday, October 22, 2012 at 01:45 PM - 03:00 PM
INTRODUCTION: The pathogenesis of UIP is unknown, but a “two hit hypothesis” has been proposed. We report a case of UIP and an unexpected finding of chronic histoplasmosis (CH). We postulate that, in predisposed individuals, chronic inflammation from histoplasmosis may cause UIP.
CASE PRESENTATION: A 61 year old man presented with months of dyspnea and years of cough. CT chest showed reticular and fibrotic changes in the lower peripheral lung fields and calcified lymph nodes. Lung biopsy showed subpleural interstitial fibrosis with honeycombing and fibroblastic foci. The mediastinal lymph node revealed necrotizing granulomas and Histoplasma capsulatum.
DISCUSSION: This is the first report of concomitant pathologically verified UIP in an individual with pathologic CH. Histoplasmosis is usually self-limited, with the rate of development of CH at about 1 per 100,000 per year. The incidence may be underestimated because of diagnostic challenges. The diagnosis of CH is based on symptoms, serological titers, radiographic findings, and microbiology. Symptoms include fever, myalgias, cough, and dyspnea. Eighty percent of patients with CH have positive serological titers of 1:32 or greater, but titers may also be positive in inactive and previously treated disease. Sputum culture sensitivity is low. Therefore, tissue pathology showing the organism and granulomas may be required. Histoplasmosis has diverse radiographic patterns. Acute infection may present with interstitial infiltrates followed by consolidation. Nodules may be seen acutely or chronically. Chronic lung cavities may develop if a pre-existing bulla becomes infected and are composed of central necrosis with surrounding fibroblastic activity (1,2). Mediastinal and hilar adenopathy are common and nodes may be calcified. Two radiographic patterns of fibrosis in response to CH have been described. Basilar fibrosis is thought to be caused by “spillover” of antigenic material from the cavity. Another rare sequela of histoplasmosis is fibrosing mediastinitis, the pathogenesis of which is not understood. A proposed etiology is release of antigenic material contained in mediastinal granulomas with subsequent inflammation and scarring (3).
CONCLUSIONS: CH is a rare disease with an unknown clinical course, but it is known to cause various types of fibrotic complications. We postulate that, in predisposed individuals, chronic inflammation due to untreated CH may cause UIP. Early detection and treatment of CH may alter the course of UIP.
1) Goodwin RA, et al. Chronic pulmonary histoplasmosis. Medicine 1976; 55:413−452.
2) Kennedy CC, et al. Redefining the Clinical Spectrum of Chronic Pulmonary Histoplasmosis. Medicine 2007; 86:252-258.
3) Loyd JE, et al. Mediastinal Fibrosis Complicating Histoplamosis. Medicine 1988; 67:295-310.
DISCLOSURE: The following authors have nothing to disclose: Alexandra McGann, Cyrus Shariat, Ravindra Rajmane
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