Pseudallescheria Boydii pneumonia in an immunocompetent host

Background

Pseudallescheria boydii is a fungal organism known to affect immunocompromised patients. This organism, a soil and water natural inhabitant, is known to cause madura foot and in severe cases, invasive infection of various organs (central nervous, cardiovascular, respiratory systems). We report an unusual case of pulmonary p. boydii pneumonia in an immunocompetent host with previous history of mycobacterium avium complex (MAC) pulmonary infection. This case highlights the importance of including uncommon fungal pathogens in the differential diagnosis of nodular pulmonary granulomatous diseases.

Case Report

A 62 year old white female presented with persistent fever, dyspnea, cough, and worsening pulmonary nodules for two months. She had a history of pulmonary MAC infection diagnosed 2 ½ years earlier. Over two years she had been treated with clarithromycin, ethambutol, and clofazimine (based on susceptibilities). There was no history of steroid or tobacco use. Upon completion of the MAC treatment course, symptoms recurred within two months and included weight loss, fatigue, chills and occasional night sweats. Physical exam was positive for bilateral ronchi. There were no ocular or skin lesions. Laboratory testing was unrevealing. Chest radiograph displayed bilateral pulmonary infiltrates. Chest computed tomogram (CT) was remarkable for diffuse bilateral nodular infiltrates, more prominent in bases, and mediastinal lymphadenopathy (Figures 1, 2). Bronchoscopic and CT guided needle biopsies were negative. An open lung biopsy was performed which was consistent with caseating granulomas; AFB and gram staining were negative. Based on high index of suspicion for recurrent infection, she resumed her previous anti-mycobacterial regimen and empiric antibiotics were started. After two months of treatment, there was lack of clinical improvement with persistent cough and intermittent fever. A repeat chest CT showed worsening of bilateral nodular infiltrates. The patient underwent a repeat bronchoscopy. Biopsy demonstrated again caseating granulomas. The BAL showed many pseudohyphae which were subsequently identified as p. boydii (Figures 3–5). Treatment with voriconazole (200 mg/day PO every 12 hours) improved her symptoms. She was able to gain weight and follow up imaging studies revealed improvement in the infiltrates.

Discussion

Pseudallesheria boydii and its asexual anamorph, Scedosporium, are ubiquitous filamentous fungi found in soil, water, and sewage. [1,2] P. boydii pneumonia affecting immunocompetent hosts is rare. [3] It is a frequent pathogen in near drowning victims, especially in areas where P. boydii is endemic. [3,4] This organism has septated, thin-walled, branching hyphae and an angioinvasive tendency [5]. Clinically, P. boydii infection has an insidious onset and is often fatal in immunocompromised hosts [6,7]. Central nervous system abscesses, rhinosinusitis, endophtalmitis, pneumonia, and skin lesions (madura foot) may be present. [8–12] In cases where a specimen is obtained, Gomori methenamine silver stains P. boydii hyphae [13].

The diagnosis of this organism is challenging as clinic findings and tomographic imaging are non specific. Chest CT abnormalities may display pulmonary cavitations or non cavitary masses, tree-in-bud nodules, ground-glass opacities, bronchial thickening, and mediastinal lymphadenopathy [5].

The antifungal treatment varies according to immunologic status. Voriconazole is the mainstay of treatment in immunocompetent hosts. P. boydii is generally sensitive to azoles. Various reports indicate an intrinsic P. boydii resistance to polyenes [14]. Surgical resection of pulmonary and central nervous system mycetomas is warranted [15,16].

Conclusions

This case highlights the importance of a high index of suspicion for superimposed fungal infections in patients who are refractory to medical treatment of bacterial pneumonitis such as MAC. Uncommon fungal pathogens should be considered in the differential diagnosis of nodular pulmonary granulomatous disease. Further diagnostic interventions are warranted when insufficient clinical improvement is observed to prevent treatment failure and adverse outcomes.