Histoplasma Antigen Detection Research Articles

Serum Aspergillus Galactomannan for the Management of Disseminated Histoplasmosis in AIDS

Disseminated histoplasmosis is an emerging infection in patients with cellular immune deficiency in non-endemic countries, caused by the migration from endemic regions and the development of travels. Diagnosis can be challenging in this context because rapid diagnostic tools such as Histoplasma antigen detection or appropriate molecular tools are generally unavailable, serology is often negative in immunosuppressed patients, and isolation of the fungus from cultures often takes several weeks. Here, we report the contribution of galactomannan serum detection for the management of an HIV-infected patient with disseminated histoplasmosis.

Pulmonary Histoplasmosis Producing a Spindle Cell “Pseudotumor”

Pulmonary spindle cell proliferations have been reported in association with a limited group of infectious agents. These lesions are rare and identified most often in the setting of immunosuppression. Because their appearance can simulate a spindle cell neoplasm, they are diagnostically treacherous, sometimes delaying antimicrobial therapy or resulting in unnecessary surgery. We report a case of a spindle pseudotumor of the lung resulting from Histoplasma capsulatum infection, a previously unreported cause of a spindle cell lesion in the lung. The patient was a 67-year-old woman in whom positron emission tomography-positive nodules developed in the left lung and left mediastinum. The patient had undergone renal transplantation and was receiving immunosuppressive therapy with mycophenolate, tacrolimus, and low-dose prednisone. Infection with H capsulatum was confirmed by culture of pleural effusion fluid, DNA probe analysis of the pleural fluid culture isolate, urinary Histoplasma antigen detection, and Grocott methenamine silver stains of tissue sections. To our knowledge, this is the first case of a spindle cell "pseudotumor" of the lung resulting from histoplasmosis. It highlights the importance of performing special stains for organisms when evaluating pulmonary spindle cell lesions in an immunocompromised host.

Diagnosis of histoplasmosis in immunosuppressed patients

To define the most appropriate studies for making a diagnosis of histoplasmosis in immunosuppressed patients. As is true of all fungal infections in immunosuppressed patients, heightened awareness of the epidemiology and clinical manifestations of histoplasmosis is essential in making an early diagnosis. Increasingly, Histoplasma antigen detection is used to help establish a diagnosis of histoplasmosis. Most of the reported data are on patients with AIDS, but limited data suggest the usefulness of this assay in other immunosuppressed patients as well. False positive reactions occur with other fungal infections, especially blastomycosis, and patients who have histoplasmosis may have a false positive serum Aspergillus galactomannan assay. The identification of the yeast phase of Histoplasma capsulatum in tissue biopsy samples and, uncommonly, in circulating blood phagocytes is also helpful in establishing a diagnosis quickly. PCR techniques have yet to prove useful for the rapid diagnosis of histoplasmosis, and serology is often negative in immunosuppressed patients. Culture remains definitive and should always be performed to confirm the results of the rapid diagnostic studies. Rapid techniques, mostly antigen detection in serum and urine and histopathological identification of Histoplasma capsulatum in tissues, are the most important rapid diagnostic tests for histoplasmosis in immunosuppressed patients.

Elimination of false‐positive Histoplasma antigenemia caused by human anti‐rabbit antibodies in the second‐generation Histoplasma antigen assay

False-positive Histoplasma antigenemia was reported in solid organ allograft recipients who had received rabbit anti-thymocyte globulin (RATG, RATG) caused by human anti-rabbit antibodies (HARA). A second-generation Histoplasma antigen detection assay was developed to overcome false positivity caused by HARA. With the second-generation assay, false-positive results were eliminated in 18 of 19 cases without reduction in the sensitivity in patients with histoplasmosis. In fact, sensitivity for detection of antigenuria in patients with acquired immunodeficiency syndrome and disseminated histoplasmosis was higher in the second-generation assay. Physicians should be aware of the potential for false-positive results in sandwich immunoassays in specimens from patients who have received RATG.

Disseminated cryptococcosis and histoplasmosis co-infection in a HIV-infected woman in France

We report the first case in Europe of co-infection with disseminated cryptococcosis and histoplasmosis. The diagnosis of invasive histoplasmosis was confirmed by microscopic examination of the anatomic right colon specimen (hemicolectomy). Histoplasma antigen detection is not yet available in France but it could have a key role in the early diagnosis of disseminated histoplasmosis co-existing with a cryptococcal infection, especially in HIV-infected African people.