Chronic Invasive Pulmonary Scedosporium apiospermum Infection in an Immunocompetent Host

Abstract

INTRODUCTION: Scedosporium apiospermum is a saprophytic fungus that typically produces localized skin and soft tissue lesions termed mycetomas. Although invasive lung disease may rarely occur due to impaired host immunity, pulmonary involvement in immunocompetent individuals is very uncommon. We report the case of a patient with a normal immune system presenting with chronic invasive pulmonary Scedosporiosis in the absence of any preexisting lung cavities. CASE PRESENTATION: A 59-year-old male presented with a 40-pound weight loss over one year. He had a good appetite, despite continued weight loss. He also complained of progressive dyspnea which began around 6 months ago. There was no history of fever/night sweats/cough and his past medical history was unremarkable. He had over 100 pack year history of smoking, with exposure to asbestos for 10 years while working on a ship. He had travelled to northern Africa several times in the past. There were no pets or birds at home. He was afebrile and his physical examination was unremarkable. A chest radiograph was performed, showing multiple nodules in the right lung. Computed tomography (CT) of the chest confirmed multiple parenchymal nodules in the right middle lobe. Pulmonary Function tests showed an obstructive pattern. The chronicity of his symptoms suggested a chronic mycobacterial, fungal or a malignant process. A fiber-optic bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy of the right middle lobe was performed. Microscopic examination of the biopsy revealed abundant fungi with septated narrow oval hyphae with spores and BAL fluid cultures grew numerous Scedosporium apiospermum colonies consistent with pulmonary Scedosporiosis. A battery of tests for any evidence of immune deficieny (including HIV, Chronic Granulomatous Disease) was repeatedly negative. The patient was started on voriconazole and his symptoms have significantly improved after 3 months of treatment. DISCUSSIONS: Scedosporium apiospermum is the anamorphic (asexual) form of Pseudallescheria boydii. It is a saprophytic fungus of class Ascomycetae found in soil, water, and feces of domesticated animals with a worldwide distribution. Known to colonize immunocompromised patients, S. apiospermum is an opportunistic pathogen that rarely causes infection in healthy hosts1. Almost 99% of infections caused by the fungus are cutaneous lesions called mycetomas. Risk factors for systemic infection include immunodeficiency, tuberculosis, sarcoidosis, and previous bacterial infections that result in cysts and cavities. Pulmonary manifestations in immunocompromised patients include fungal ball formation, allergic bronchopulmonary mycosis, pneumonitis and disseminated disease (with mortality rates of 75% or more). Infections in immunocompetent hosts are often localized and invasive pulmonary infection in the absence of concomitant cavitary lesions as in the index case is very uncommon. Diagnosis involves isolation and culture in Sabouraud and most standard media where the mold matures after 7 days of incubation, producing tadpole or sperm shaped asexual conidia. Microbiologic confirmation is essential as the clinical picture of S. apiospermum often mimics findings caused by Aspergillus and Fusarium though the antifungal susceptibility patterns are markedly different. Scedosporium apiospermum is resistant to amphotericin B. Voriconazole/Posaconazole are the agents of choice for treating cutaneous, pulmonary infections and disseminated disease2. The optimal duration of therapy has to be individulized. In immunocompetent hosts, antifungal treatment is continued for 3 to 6 months while immunocompromised individuals may require treatment for years. CONCLUSION: This case highlights that chronic weight loss in presence of pulmonary nodules in immunocompetent hosts should prompt consideration of chronic fungal infections in the differential diagnosis. Index of suspicion should be high for rare infections like Scedosporium. Microbiologic confirmation is essential for appropriate antifungal therapy.