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Mayo Clinic Scottsdale Scottsdale, AZ 85259
Pseudallescheriasis is an uncommon and not well-known fungal disease that can simulate aspergillosis clinically, radiologically, and morphologically at pathology. Awareness of this potentially lethal infection is important to obtain the correct diagnosis and to provide adequate treatment for patients.
A 78-year-old woman, treated with interferon and radiation for melanoma, presented with an enlarging complex cystic mass of the right middle lobe, which was suspicious for metastasis (Fig. 1A). CT-guided biopsy of the lung mass, which showed findings negative for malignancy, was suggestive of aspergillosis on the basis of hyphae. The patient was treated with oral itraconazole and then IV amphotericin B for suspected invasive aspergillosis. Subsequently, she complained of bilateral ophthalmitis with impaired vision. MR imaging revealed multiple cerebral ring—enhancing lesions compatible with abscesses (Fig. 1B). In addition, there was involvement of the right optic nerve and right cavernous sinus (Fig. 1C). The patient underwent left vitrectomy, which yielded Pseudallescheria boydii on fungal cultures. Follow-up chest radiographs showed worsening lung invasion with bilateral cavitating nodules (Fig. 1D). Concomitantly, the patient developed multiple maculopapular skin lesions with scabbing on the face, body, and extremities. Her treatment was changed to IV itraconazole for disseminated pseudallescheriasis. Exacerbation of pulmonary infection marked the clinical course and precipitated the patient's death.
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P. boydii, also known as Allescheria boydii, is an opportunistic fungus with the anamorph name of Scedosporium apiospermum. Present in soil, decaying vegetation, and stagnant or polluted water throughout the world, it is responsible for skin and systemic infections. Cutaneous involvement by direct inoculation consists of mycetoma, which is one of the main causes of Madura foot [1, 2]. Pseudallescheriasis, the systemic manifestation, is contracted through inhalation; near-drowning accident; or direct implantation from trauma, surgery, or other iatrogenic causes. It targets lung, bone, central nervous system, sinuses, eyes, heart, soft tissues, and skin [1,2,3,4]. The localized form of pseudallescheriasis exhibits subacute or chronic courses in previously healthy patients. Disseminated and invasive pseudallescheriasis is encountered in patients who are debilitated and immunocompromised as a result of AIDS, immunosuppressive therapy, hematologic malignancy, diabetes, or transplantation. Lung infection mimics aspergillosis, with fungus balls in preexisting cavities and abscesses with central cavitation [3]. Necrotizing pneumonitis is common in immunocompromised patients. Central nervous system manifestations, either by direct or hematogenous extension, include cerebral abscesses, meningitis, cerebritis, ventriculitis, and intracranial vascular involvement with imaging features similar to those of aspergillosis [4]. Ocular infection encompasses keratitis, endophthalmitis, panophthalmitis, and, as seen in our patient, optic neuropathy.
Tissue sampling of abscesses provides hyaline, septate, branched, and hematoxylinophilic hyphae of P. boydii. Morphologically, these hyphae are often indistinguishable from those of Aspergillus organisms and other hyaline hyphomycetes [1, 2]. Culture and serologic analysis are essential to achieve definitive identification of the fungus. Correct diagnosis of pseudallescheriasis is necessary to implement therapy, which, unfortunately, is not well established for this species. P. boydii is resistant to amphotericin B. IV miconazole, ketonazole, and itraconazole with surgery appear to be effective for focal infection and abscesses of the central nervous system [1, 2]. Treatment with itraconazole and voriconazole with a favorable outcome has been reported for disseminated and invasive pseudallescheriasis, which frequently bears a pessimistic prognosis in immunocompromised patients [1,2,3,4].
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  K. J. Cortez, E. Roilides, F. Quiroz-Telles, J. Meletiadis, C. Antachopoulos, T. Knudsen, W. Buchanan, J. Milanovich, D. A. Sutton, A. Fothergill, et al. Infections Caused by Scedosporium spp. Clin. Microbiol. Rev., January 1, 2008; 21(1): 157 - 197. [Abstract] [Full Text] [PDF]
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