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Histoplasmosis in Travelers
By Carol A. Kemper, MD, FACP
Clinical Assistant Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara, Valley Medical Center
Dr. Kemper does research for Abbott Laboratories and Merck.
This article originally appeared in the April issue of Infectious Disease Alert.
Source: Buitrago MJ, et al. Histoplasmosis and paracoccidioidomycosis in a non-endemic area: A review of cases and diagnosis. J Travel Med 2010;18:26-33.
Twice in the past 2 years I've encountered pulmonary histoplasmosis in travelers returning from Central America (Mexico and Costa Rica), and both times the diagnosis proved challenging. One case, in particular, was a 60-year-old man who had traveled to Costa Rica for 1 week and then presented with fever, persistent dry cough, malaise, and complaints of memory loss. Only a biopsy of lung tissue confirmed the diagnosis of carcinoid tumor, bronchiolitis obliterans, and histoplasmosis (based on histopathology; cultures were negative).
These authors at the Spanish Mycology Reference Laboratory in Madrid, Spain, describe their experience with the laboratory detection of histoplasmosis and paracoccidioidomycosis (PCM) in returning travelers and immigrants, including the use of a novel PCR-based technique based on DNA amplification of the internal transcriber spacer region of H. capsulatum var. capsulatum, H. capsulatum var. duboisii, and P. brasiliensis. Precipitating antibodies were detected using immunodiffusion assay.
Since 2006, histoplasmosis was diagnosed in 9 returning travelers and 30 immigrants; most had come from South America (83%), Africa, or both. The 9 travelers had no underlying disease, and were diagnosed with probable histoplasmosis based on positive immunodiffusion test results. The organism was not cultured in any of these patients. RT-PCR was positive in 5, including 3 of 7 serum specimens, 2 of 3 lung biopsies, and 1 of 1 sputum specimen.
In contrast, all 30 immigrants were diagnosed with disseminated histoplasmosis; 97% of these were HIV-infected and the remaining patients had a hematologic malignancy. Of these, 97% were diagnosed with proven histoplasmosis based on a positive culture or visualization of the organism in tissue specimens; only 1 patient was diagnosed based on the results of RT-PCR alone. Immunodiffusion testing was performed in 20 patients, and was positive in 8 (40%), whereas RT-PCR was positive in 24 of 27 patients tested (89%; this included plasma or serum, bone marrow biopsy, or other tissue biopsy). Three patients from Africa were found to have H. capsulatum var. duboisii based on RT-PCR results.
Six patients, all immigrants from South America, were diagnosed with PCM; all 6 had positive immunodiffusion assays for PCM (which were weakly positive in 3), and all 6 had a positive RT-PCR of plasma or serum, bronchoalveolar lavage, lung biopsy, or other biopsy.
Pulmonary histoplasmosis should be suspected in any traveler returning from Central or South America with fever, headache, malaise, dry cough, and chest discomfort (especially if they have visited caves), although confirming the diagnosis may be challenging. Immunodiffusion assays are helpful in many patients, but it may be necessary to obtain tissue.