Histoplasmosis

Histoplasmosis: diagnostic challenges

Histoplasmosis is an infection usually caused by a fungal pathogen that, in most cases, occurs in the respiratory tract, which explains the high frequency of clinical manifestations in the lungs. (1) This mycosis is endemic in the Americas (Mississippi and Ohio River Valley, USA; Central and South America; and the West Indies), while reports in areas of Asia, Africa, Australia, and Oceania are mainly asso­ciated with the pandemic of acquired immune deficiency syndrome (AIDS). In Europe, cases are on the rise because of the speculation of a global distribution of histoplasmosis, and emphasis has been on improving methods for its diagnosis. (2,3)

Accuracy of Buffy Coat in the Diagnosis of Disseminated Histoplasmosis in AIDS-Patients in an Endemic Area of Brazil

The buffy coat is obtained routinely for disseminated histoplamosis (DH) diagnosis in Ceará, Brazil. The aim of this study is to describe the accuracy of staining smears for Histoplasma in the buffy coat of AIDS-patients with DH. From 2012-2013, all results of stained buffy coat smears and culture for fungi performed at São José Hospital were recorded. In total, 489 buffy coats of 361 patients were studied; 19/361 (5.3%; 95%CI = 2.9-7.6%) had positive direct examination stained smears for Histoplasma and 61/361 (16.9%; 95%CI = 13.0-20.8%) had growth in culture. For those with positive Histoplasma cultures, the CD4 count was significantly lower (139.3 vs. 191.7cells/µL; p = 0.014) than others, and death was 18%. The sensitivity and specificity of stained smears was 25.9% and 100%, respectively. A second test, performed up to 36 days from the first one, increased the sensitivity of stained smears to 32.2%. Stained smears of buffy coat have low accuracy; nonetheless, they are easy to perform and can give a quick diagnosis in low-resource endemic areas. Despite the decrease in mortality, it is not yet to the low levels observed in areas that have better and more efficient methods.

Histoplasmosis, heart failure, hemolysis and haemophagocytic lymphohistiocytosis

Histoplasmosis is an endemic mycosis with global distribution, primarily reported in immunocompromised individuals. A 29-year old immunocompetent male presented with fever, hepatosplenomegaly and pancytopenia. His peripheral blood showed features suggestive of intravascular hemolysis and echocardiography showed features suggestive of pulmonary arterial hypertension. Bone marrow showed yeast with morphology suggestive of Histoplasma capsulatum. Further investigations revealed hyperferritinemia, hypofibrinogenemia and increased triglycerides. With a diagnosis of progressive disseminated histoplasmosis with secondary Haemophagocytic lymphohistiocytosis, he was successfully treated with amphotericin B followed by itraconazole. We report this case to highlight the atypical and rare manifestations of histoplasmosis.

Histoplasma capsulatum periprosthetic knee infection complicated by autoimmune-mediated systemic inflammatory response syndrome

Histoplasma capsulatum periprosthetic knee infection has rarely been reported in the literature due to its low frequency. Notwithstanding, it is important to keep it among the differential diagnoses to avoid delays in treatment. The current report presents the case of infectious knee monoarthritis in an immunocompetent patient after unicompartmental knee arthroplasty. The joint infection was accompanied by disseminated histoplasmosis, which initiated an autoimmune reaction, ensuing a systemic inflammatory response syndrome. The management protocol used in this case was successful and included staged arthroplasty reconstruction combined with chronic antifungal and steroid pharmacotherapy. Approximately 4 years after total knee arthroplasty revision, there were no clinical signs of localized or systemic infection.

Mapping Histoplasma capsulatum Exposure, United States

Maps of Histoplasma capsulatum infection prevalence were created 50 years ago; since then, the environment, climate, and anthropogenic land use have changed drastically. Recent outbreaks of acute disease in Montana and Nebraska, USA, suggest shifts in geographic distribution, necessitating updated prevalence maps. To create a weighted overlay geographic suitability model for Histoplasma, we used a geographic information system to combine satellite imagery integrating land cover use (70%), distance to water (20%), and soil pH (10%). We used logistic regression modeling to compare our map with state-level histoplasmosis incidence data from a 5% sample from the Centers for Medicare and Medicaid Services. When compared with the state-based Centers data, the predictive accuracy of the suitability score–predicted states with high and mid-to-high histoplasmosis incidence was moderate. Preferred soil environments for Histoplasma have migrated into the upper Missouri River basin. Suitability score mapping may be applicable to other geographically specific infectious vectors.

Seroprevalence of Histoplasmosis in Somali, Burmese, and Hmong Refugees Residing in Thailand and Kenya

Histoplasmosis is known to be endemic to the Midwestern United States, but cases have been reported throughout much of the world. Somali, Hmong, and Burmese (ethnically Karen) persons make up some of the largest refugee populations coming the United States in recent years. Yet, information about risk of Histoplasma capsulatum infection amongst these populations is limited. This study used the CDC Migrant Serum Bank to test ~100 samples from each of Somali, Burmese, and Hmong U.S.-bound refugees. Samples were tested by enzyme immunoassay for Histoplasma capsulatum IgG. Overall 1% (2/299) of refugee serum samples were positive for H. capsulatum IgG. One of 99 samples obtained from Hmong refugees was positive, and the other positive sample came from among 100 Burmese refugee samples. H capsulatum IgG positivity was detected at low levels in Hmong and Burmese refugees. No IgG positivity was detected among 100 Somali refugees.

Emerging and reemerging fungal infections

Fungal infections throughout the world appear to be increasing. This may in part be due to the increase in the population of patients that are susceptible to otherwise rare fungal infections resulting from the use of immune modulating procedures such as hematopoietic stem cell transplants and drugs like tissue necrosis factor antagonists. Histoplasma capsulatum, an endemic fungus throughout North and South America, is reemerging among HIV+ patients in Central and South America and among patients taking tissue necrosis factor antagonists and other biologics in North America. Fusarium species, a relatively rare fungal infection, is reemerging worldwide in the immunocompromised populations, especially those who are neutropenic like hematopoietic stem cell transplant recipients. A new yeast species is currently emerging worldwide: Candida auris, unknown just a decade ago. It is causing large healthcare-associated outbreaks on four continents and is spreading throughout the world through patient travel. In this review the epidemiology, pathology, detection and treatment of these three emerging and reemerging fungi will be discussed.

Inadequate diagnostics: the case to move beyond the bacilli for detection of meningitis due to Mycobacterium tuberculosis

Tuberculosis (TB) meningitis is extremely difficult to diagnose due to its pauci-bacillary disease nature and new techniques are needed. Improved test sensitivity would allow for greater clinician confidence in diagnostic testing and has the potential to improve patient outcomes. Traditional microbiologic and molecular tests for TB meningitis focus on detection of TB bacilli and are inadequate. Smear microscopy is rapid but only ~10-15  % sensitive. Culture has 50-60  % sensitivity but is slow. Xpert MTB/Rif Ultra is a rapid, automated PCR-based assay with ~70  % sensitivity versus clinical case definition. Thus, even the best current testing may miss up to 30  % of cases. Clinicians are often left to treat empirically with prolonged regimens with significant side effects or risk a missed case that would result in death. Rather than relying strictly on microbiologic or molecular testing to diagnose TB meningitis, we propose that testing of CSF for biomarkers of host response may have an adjunctive role to play in improving the diagnosis of TB meningitis.

Histoplasmosis among HIV-Infected Patients in Japan: a Case Report and Literature Review

Histoplasmosis is occasionally encountered in non-endemic countries owing to more frequent international travel and migration, as well as an increase in the number of vulnerable hosts (e.g., patients with cellular immunodeficiencies). However, the diagnosis of endemic mycoses may be challenging because of its rarity and the limited availability of diagnostic tests. We report a case of disseminated histoplasmosis in a human immunodeficiency virus (HIV)-infected Japanese man who had often travelled to histoplasmosis-endemic countries. We also reviewed the reported cases of HIV-associated histoplasmosis in Japan. To the best of our knowledge, this is the ninth case report of co-infection with Histoplasma and HIV in Japan and the second involving a Japanese patient. This case emphasizes the importance of noting the details of not only the present residence of patients, but also their previous residence and travels. If histoplasmosis is suspected, physicians should inform laboratory personnel that fungal cultures should be incubated for 6 weeks, and compliance with biosafety guidelines for handling the specimens should be practiced. Since death occurs in nearly 50% of HIV-associated histoplasmosis cases in Japan, early recognition, timely diagnosis, and appropriate treatment are mandatory.

Endemic fungal infections in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention and management of blastomycosis, histoplasmosis, and coccidioidomycosis in the pre- and post-transplant period. Though each of these endemic fungal infections has unique epidemiology and clinical manifestations, they all share a predilection for primary pulmonary infection and may cause disseminated infection, particularly in immunocompromised hosts. Culture remains the gold standard for definitive diagnosis, but more rapid diagnosis may be achieved with direct visualization of organisms from clinical specimens and antigen-based enzyme immunoassay assays. Serology is of limited utility in transplant recipients. The mainstay of treatment for severe infections remains liposomal amphotericin followed by a step-down azole therapy. Cases of mild to moderate severity with no CNS involvement may be treated with azole therapy alone. The newer generation azoles provide additional treatment options, but supported currently with limited clinical efficacy data. Azole therapy in transplant recipients presents a unique challenge owing to the drug-drug interactions with immunosuppressant agents. Therapeutic drug monitoring of azole levels is an essential component of effective and safe therapy. Infection prevention centers around minimizing epidemiological exposures, early clinical recognition, and azole prophylaxis in selected individuals.

Histoplasmosis, An Underdiagnosed Disease Affecting People Living With HIV/AIDS in Brazil: Results of a Multicenter Prospective Cohort Study Using Both Classical Mycology Tests and Histoplasma Urine Antigen Detection

Background

Histoplasmosis is highly endemic in the American continent. This condition is associated with a high mortality, particularly in people living with HIV/AIDS (PLWHA). Diagnosis of histoplasmosis is usually late in South America, as Histoplasma antigen detection is rarely available. Here we determined the prevalence, risk factors, and outcome of histoplasmosis in PLWHA in Brazilian hospitals.

Methods

This was a prospective cohort study (2016-2018) involving 14 tertiary medical centers in Brazil. We included hospitalized PLWHA presenting with fever and additional clinical findings. Patients were investigated at each participant center with classical mycology methods. Also, Histoplasma antigen detection was performed in urine samples (IMMY). Probable/proven histoplasmosis was defined according to European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group/National Institute of Allergy and Infectious Diseases Mycoses Study Group criteria.

Results

From 616 eligible patients, 570 were included. Histoplasmosis was identified in 21.6% (123/570) of patients. Urine antigen testing increased the diagnostic yield in 53.8%, in comparison with standard mycology methods. Variables independently associated with histoplasmosis were CD4+ count <50 cells/mm³, use of an antiretroviral (protective effect), and sample collection in the Northeast region of Brazil. Dyspnea at presentation was independently associated with death. Histoplasmosis was more frequent than tuberculosis in patients with low CD4+ counts. Overall 30-day mortality was 22.1%, decreasing to 14.3% in patients with antigen-based diagnosis.

Conclusions

Histoplasmosis is a very frequent condition affecting PLWHA in Brazil, particularly when CD4+ counts are lower than 50 cells/mm³. Antigen detection may detect earlier disease, with a probable impact on outcomes. Access to this diagnostic tool is needed to improve clinical management of PLWHA in endemic countries.

Clinical outcomes and cortical reserve in adrenal histoplasmosis-A retrospective follow-up study of 40 patients

OBJECTIVE

Detailed studies of Addison's disease resulting from disseminated adrenal histoplasmosis (AH) are not available. We describe the presentation and prognosis of AH and cortisol status before and after antifungal therapy.

DESIGN

Single-centre retrospective hospital-based study of 40 consecutive adults with AH [39 males; age (mean ± SD) 53 ± 11 years] was conducted between 2006 and 2018. The median duration of follow-up was 2.5 years (range 0.2-12 years).

PATIENTS AND METHODS

AH was diagnosed by bilateral adrenal enlargement on CT scan and presence of Histoplasma by histology and/or culture of biopsied adrenal tissue. All patients received oral itraconazole and, if required, amphotericin B as per guidelines. ACTH-stimulated serum cortisol (normal > 500 nmol/L) was measured in 38 patients at diagnosis and re-tested after one year of antifungal therapy in 21 patients.

RESULTS

Seventy-three per cent of patients had primary adrenal insufficiency (PAI) and one-third had an adrenal crisis at presentation. HIV antibody was negative in all patients. Of the 29 patients who completed antifungal therapy, 25 (86%) were in remission at last follow-up. Overall, 8 (20%) patients died: three had a sudden death, four had severe histoplasmosis and one died due to adrenal crisis. No patient with PAI became eucortisolemic on re-testing after one year of antifungal therapy. Of the eight patients with normal cortisol at diagnosis, two developed adrenal insufficiency on follow-up.

CONCLUSION

All patients with AH tested negative for HIV antibody. While patients achieved a high rate of clinical remission after antifungal therapy, overall mortality was significant. Cortisol insufficiency did not normalize despite treatment.

A case report of disseminated histoplasmosis and concurrent cryptococcal meningitis in a patient treated with ruxolitinib

Background

Ruxolitinib is a highly potent janus kinase inhibitor that places its users at risk for various bacterial infections and viral reactivation. However new reports are also emerging that suggest greater immunosuppression and risk for fungal disease.

Case presentation

We report the case of a 51 year-old veteran from Guam, treated with ruxolitinib for polycythemia vera, who developed disseminated histoplasmosis and concurrent cryptococcal meningitis.

Conclusion

This case draws attention to the degree of immunosuppression that may be seen with this drug and the need for heightened vigilance for opportunistic infections in those treated with inhibitors of janus kinase/signal transducers and activators of transcription (JAK/STAT) such as ruxolitinib.

Disseminated pulmonary histoplasmosis in immunocompetent patients: a common epidemiological exposure

We describe the initial presentation, diagnostic work-up and treatment of three adult immunocompetent men who presented within a short time frame of each other to an academic medical centre with acute respiratory distress syndrome. Their presentation was found to be secondary to a large inoculum of histoplasmosis from remodelling a building with bat droppings infestation. We discuss the pathophysiology of histoplasmosis and highlight the importance of exposure history in patients with acute respiratory failure and why patients with the occupational risk of exposure to fungal inoculum should wear protective respirator gear.

Mycobiome Sequencing and Analysis Applied to Fungal Community Profiling of the Lower Respiratory Tract During Fungal Pathogenesis

Invasive fungal infections are an increasingly important cause of human morbidity and mortality. We generated a next-generation sequencing (NGS)-based method designed to detect a wide range of fungi and applied it to analysis of the fungal microbiome (mycobiome) of the lung during fungal infection. Internal transcribed spacer 1 (ITS1) amplicon sequencing and a custom analysis pipeline detected 96% of species from three mock communities comprised of potential fungal lung pathogens with good recapitulation of the expected species distributions (Pearson correlation coefficients r = 0.63, p = 0.004; r = 0.71, p < 0.001; r = 0.62, p = 0.002). We used this pipeline to analyze mycobiomes of bronchoalveolar lavage (BAL) specimens classified as culture-negative (n = 50) or culture-positive (n = 39) for Blastomyces dermatitidis/gilchristii, the causative agent of North America blastomycosis. Detected in 91.4% of the culture-positive samples, Blastomyces dominated (>50% relative abundance) the mycobiome in 68.6% of these culture-positive samples but was absent in culture-negative samples. To overcome any bias in relative abundance due to between-sample variation in fungal biomass, an abundance-weighting calculation was used to normalize the data by accounting for sample-specific PCR cycle number and PCR product concentration data utilized during sample preparation. After normalization, there was a statistically significant greater overall abundance of ITS1 amplicon in the Blastomyces-culture-positive samples versus culture-negative samples. Moreover, the normalization revealed a greater biomass of yeast and environmental fungi in several Blastomyces-culture-positive samples than in the culture-negative samples. Successful detection of Coccidioides, Scedosporium, Phaeoacremonium, and Aspergillus in 6 additional culture-positive BALs by ITS1 amplicon sequencing demonstrates the ability of this method to detect a broad range of fungi from clinical specimens, suggesting that it may be a potentially useful adjunct to traditional fungal microbiological testing for the diagnosis of respiratory mycoses.

Disseminated Central Nervous System Histoplasmosis: A Case Report

Central nervous system (CNS) histoplasmosis is a rare manifestation of disease, often misdiagnosed due to the wide spectrum of neurological presentation. We present a rare case of CNS histoplasmosis in a 62-year-old male with untreated myeloproliferative disease who presented with altered mental status. This case emphasizes the clinical presentation and diagnostic difficulty in a patient with CNS histoplasmosis. We also highlight the importance of implementing a multidisciplinary approach in the medical management of disseminated histoplasmosis with CNS involvement.

Diagnostic Dilemma of Disseminated Histoplasmosis Mimicking Hemophagocytosis Lymphohistiocytosis in Patient with Rheumatoid Arthritis on Anti-TNF Therapy: Case Report and Review of the Literature

Tumor necrosis factor inhibitors (TNFi) have become the cornerstone for the treatment of rheumatoid arthritis and other systemic autoimmune conditions. However, these biologic DMARDs can lead to various opportunistic infections such as viral infection, tuberculosis, and histoplasmosis. Furthermore, these biologics can also cause severe systemic inflammatory reactions known as hemophagocytosis lymphohistiocytosis (HLH) that can lead to multiorgan failure and high mortality. Due to overlapping clinical features and time-intensive microbiological culture methods, distinguishing between HLH and opportunistic infections can be challenging early in the disease course. We present a similar situation with our patient where the patient met the diagnostic criteria for HLH however was found to have disseminated histoplasmosis. This case uniquely evaluates the utility of the HLH diagnostic criteria and hemophagocytosis for accurate diagnosis of HLH.

Phylogenetic analysis of Histoplasma capsulatum var duboisii in baboons from archived formalin-fixed, paraffin embedded tissues

Histoplasma capsulatum var. duboisii (Hcd) infections have been well documented to cause chronic granulomatous disease, mainly involving the skin of baboons and humans in African countries primarily. This retrospective study classified the subspecies of Histoplasma and developed a phylogenetic tree utilizing DNA sequences extracted from formalin-fixed, paraffin embedded (FFPE) tissues from 9 baboons from a research colony in Texas histologically diagnosed with Hcd. Based on sequence analysis of ITS-2, Tub-1, and ARF, Hcd isolated from the archived samples closely aligns with the African clade and has 88% sequence homology with a sample isolated from an individual in Senegal.

Endemic pulmonary fungal diseases in immunocompetent patients: an emphasis on thoracic imaging

INTRODUCTION

Systemic endemic mycoses are prevalent in specific geographical areas of the world and are responsible for high rates of morbidity and mortality in these populations, and in immigrants and travelers returning from endemic regions. The most common fungal infections that can affect the lungs of immunocompetent patients include histoplasmosis, coccidioidomycosis, paracoccidioidomycosis, blastomycosis, sporotrichosis, aspergillosis, and cryptococcosis. Diagnosis and management of these diseases remain challenging, especially in non-endemic areas due to the lack of experience. Therefore, recognition of the various radiologic manifestations of pulmonary fungal infections associated with patients' clinical and epidemiologic history is imperative for narrowing the differential diagnosis. Areas covered: This review discusses the clinical and radiological findings of the main endemic fungal diseases affecting the lungs in immunocompetent patients. Specific topics discussed are their etiology, epidemiology, pathogenesis, clinical manifestations, methods of diagnosis, pathology and main imaging findings, especially in computed tomography. Expert commentary: Imaging plays an important role in the diagnosis and management of pulmonary fungal infection and may reveal useful signs. Although definitive diagnosis cannot be made based on imaging features alone, the use of a combination of epidemiologic, clinical and imaging findings may permit the formulation of an adequate differential diagnosis.

Role of western blot assay for the diagnosis of histoplasmosis in AIDS patients from a National Institute of Infectious Diseases in Rio de Janeiro, Brazil

BACKGROUND

Histoplasmosis is a frequent fungal infection in HIV/AIDS patients, with high morbimortality rates when diagnosis and treatment are delayed. Antibody detection, which is faster than the gold standard culture test, hastens the laboratory investigation.

OBJECTIVES

To evaluate the role of WB for antibody detection in the diagnosis of histoplasmosis among HIV/AIDS patients.

PATIENTS AND METHODS

Fifty patients with proven or probable histoplasmosis were included. Clinical, epidemiological and laboratory data were described in the same population after a review of their medical records. WB was performed using deglycosylated histoplasmin.

RESULTS

About 82% of patients were adult males and the mean age was 39.3 years. CD4⁺ T lymphocyte count less than 150 cells/mm³ was observed in 62% patients. Antibodies against Histoplasma capsulatum M antigen were detected in 62% of patients, and against both M and H antigens in 28% of individuals. Sera from 10% of patients were nonreactive. Histoplasmosis was the first opportunistic infection in 38% of the cases. Disseminated and pulmonary histoplasmosis occurred in 84% and 16% of patients, respectively. The overall mortality was 16%.

CONCLUSION

WB could be useful for the histoplasmosis diagnosis in HIV/AIDS patients because of its easefulness and good sensitivity in a population where antibody production is hampered.

Cryptococcal meningitis is a cause for cross-reactivity in cerebrospinal fluid assays for anti-Histoplasma, anti-Coccidioides and anti-Blastomyces antibodies

BACKGROUND/OBJECTIVES

Antibody detection is commonly used for diagnosis of histoplasmosis, and cross-reactions have been recognised due to endemic mycoses but not cryptococcosis. We observed cross-reactions in an anti-Histoplasma antibody enzyme immunoassay (EIA) in the cerebrospinal fluid (CSF) from a patient with cryptococcal meningitis and sought to assess the risk of cross-reactive anti-Histoplasma antibodies in persons with cryptococcal meningitis.

METHODS

An anti-cryptococcal antibody EIA was developed to measure CSF antibody response in HIV-infected subjects from Kampala, Uganda and previously healthy, HIV-negative subjects at the National Institutes of Health (NIH) with cryptococcal meningitis. Specimens were tested for cross-reactivity in assays for IgG anti-Histoplasma, anti-Blastomyces and anti-Coccidioides antibodies.

RESULTS

Among 61 subjects with cryptococcal meningitis (44 Kampala cohort, 17 NIH cohort), elevated CSF anti-cryptococcal antibody levels existed in 38% (23/61). Of the 23 CSF specimens containing elevated anti-cryptococcal antibodies, falsely positive results were detected in antibody EIAs for histoplasmosis (8/23, 35%), coccidioidomycosis (6/23, 26%) and blastomycosis (1/23, 4%). Overall, 2% (2/81) of control CSF specimens had elevated anti-cryptococcal antibody detected, both from Indiana.

CONCLUSIONS

Cryptococcal meningitis may cause false-positive results in the CSF for antibodies against Histoplasma, Blastomyces and Coccidioides. Fungal antigen testing should be performed to aid in differentiating true- and false-positive antibody results in the CSF.

Histoplasma Capsulatum: Mechanisms for Pathogenesis

Histoplasmosis, caused by the dimorphic environmental fungus Histoplasma capsulatum, is a major mycosis on the global stage. Acquisition of the fungus by mammalian hosts can be clinically silent or it can lead to life-threatening systemic disease, which can occur in immunologically intact or deficient hosts, albeit severe disease is more likely in the setting of compromised cellular immunity. H. capsulatum yeast cells are highly adapted to the mammalian host as they can effectively survive within intracellular niches in select phagocytic cells. Understanding the biological response by both the host and H. capsulatum will facilitate improved approaches to prevent and/or modify disease. This review presents our current understanding of the major pathogenic mechanisms involved in histoplasmosis.

Histopathology

During the last 30 years, advances in intensive and critical care units, organ transplantation, concomitant use of immunosuppressive drugs, and increasing prevalence of chronic diseases, malnutrition, and other debilitating conditions, as well as the human immunodeficiency virus pandemic, have increased the incidence of systemic mycotic diseases, the most serious form of fungal diseases are the ones that comprise the central nervous system, representing the most dangerous clinical situations. In those cases, starting an adequate therapy through a rapid and assertive diagnosis is absolutely necessary. Considering the fastidious microbiological nature of some fungi (longtime requirement, specific culture conditions, and biohazard issues), as well as the lack of alternative testing availability, a rapid diagnosis is always challenging. When a tissue or liquid specimen is available, its pathological analysis constitutes a rapid and cost-effective way to provide a presumptive or definitive diagnosis of an invasive fungal infection; however, microbiologists, pathologists, and clinicians need to be aware of the limitations of microscopical diagnosis. In this chapter, we review the usual histological presentation of the most frequent central nervous system fungal infections.

Endemic Mycoses in Solid Organ Transplant Recipients

The endemic mycoses are a group of thermally dimorphic fungal pathogens occupying a specific geographic range. In North America, the chief endemic mycoses are histoplasmosis, coccidioidomycosis, and blastomycosis. Endemic fungi can cause serious infections in solid organ transplant recipients from primary infection, reactivation of latent disease, or donor-derived infection.

Acute histoplasmosis in immunocompetent travelers: a systematic review of literature

Background

Histoplasmosis is a fungal infection highly endemic in the American continent. The disease can be severe in immunocompromised subjects. In immunocompetent subjects the clinical manifestations are variable. Aim of this work was to review the cases of acute histoplasmosis in immunocompetent travelers reported in literature.

Methods

A systematic review of literature was conducted. Electronic search was performed in Pubmed and LILACS. Two reviewers independently extracted data on demographic, clinical and radiological features, and treatment. Cases were classified according to Wheat’s definitions.

Results

Seventy-one studies were included in the analysis, comprising a total of 814 patients. Twenty-one patients diagnosed at the Centre of Tropical Diseases, Negrar (VR), Italy were also included. The most common travel destination was Central America (168 people, 29.8%); the most common way of exposure to histoplasma was the exploration of caves and/or contact with bat guano (349 people, 60.9%). The multivariate logistic regression model showed association between the development of disseminated histoplasmosis (DH) and activities that involved the exploration of caves and/or the contact with bats’ guano (adjusted OR: 34.20 95% CI: 5.29 to 220.93) or other outdoor activities (adjusted OR: 4.61 95% CI: 1.09 to 19.56). No significant difference in the attack rate between countries of destination was observed (p-value: 0.8906, Kruskal-Wallis test).

Conclusions

Histoplasmosis often causes no or mild symptoms in immunocompetent individuals, although a severe syndrome may occur. The infection can mimic other diseases, and the epidemiological risk of exposure is an important clue to raise the index of suspicion.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3476-z) contains supplementary material, which is available to authorized users.

In vitro activity of isavuconazole against fluconazole-resistant isolates of Histoplasma capsulatum

No clinical trials for histoplasmosis have been performed with the newer azoles, leaving itraconazole as the azole of choice. In vitro studies suggest that Histoplasma capsulatum from patients that relapse on fluconazole has higher minimum inhibitory concentrations (MICs) to fluconazole and voriconazole but not itraconazole and posaconazole. The newest azole, isavuconazole, shares structural similarity to voriconazole, but to date nobody has explored emergence of resistance. In vitro susceptibilities to isavucoanzole and fluconazole were performed on previously obtained isolates from the patients who relapsed on fluconazole therapy. Susceptibilities were determined by NCCLS method M27A developed for yeasts, as modified for H. capsulatum. The change in the MIC from the primary to the relapse isolate was tested using Wilcoxon Rank-Sum for paired data. Among the primary isolates, the median MICs were 1.0 (range 0.25 to 4.0) μg/ml for fluconazole and ≤0.007 (range ≤0.007 to 0.015) μg/ml for isavuconazole. In the group of relapsed isolates, the median MICs rose to 8.0 (range 0.25 to 64.0) μg/ml for fluconazole and remained unchanged at ≤0.007 (range ≤0.007 to 0.015) μg/ml for isavuconazole (P < .001). Only one isolate exhibited a nonsignificant increase in MIC to isavuconazole. Histoplasma isolates from patients who relapsed on fluconazole did not have an elevation in MICs to isavuconazole. This differs from the results previously seen with voriconazole and suggests that despite a closer structural similarity to voriconazole than itraconazole and posaconazole, isavuconazole has a higher barrier to resistance and may be effective as therapy for histoplasmosis.

Histoplasmosis-induced ileal perforation in a patient with acquired immune deficiency syndrome: Case report

Intestinal involvement with disseminated histoplasmosis is common in some populations infected with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), especially in those who come from tropical zones. We report the case of a 29‐year‐old male patient, from a tropical zone, with HIV infection and a CD₄ value less than 50 cells/mm³, with a history of abdominal pain, fever, diarrhea, and weight loss. On presentation, he was pale, sweaty, and had abdominal rebound tenderness. Laboratory findings demonstrated microcitic hipocromic anemia, azoemia, and hypoalbuminemia. Abdominal‐X‐rays revealed pneumoperitoneum and air fluid levels. He underwent surgery, and a 1‐cm perforation proximal to ileocecal valve was found. A resection and an ileostomy were performed. Histopathology identified caseating granulomas with yeast, compatible with histoplasmosis. He was treated with anfotericin B plus itraconazol with clinical improvement.

Histoplasma capsulatum causing sinusitis: a case report in French Guiana and review of the literature

Background

American histoplasmosis is a mycosis caused by Histoplasma capsulatum. A variety of clinical features of histoplasmosis have been commonly described ranging from asymptomatic infections to severe pulmonary infections. In immunocompromised individuals, progressive disseminated forms are frequent, leading to fatal outcome if untreated. However, H. capsulatum sinusitis is unusual with a few cases documented over the last three decades and may be underdiagnosed or confused with other fungal aetiologies, especially outside endemic regions.

Case presentation

In this study, we report an atypical case of Histoplasma capsulatum sinus fungus ball-like in a patient with Acquired Immunodeficiency Syndrome due to Human Immunodeficiency Virus complicated by a disseminated histoplasmosis with a death ending. Diagnosis relied on CT-Scan imaging and on both direct examination of H. capsulatum yeast forms (Gomory methenamine Grocott) in the sinus specimen (aspirate, biopsy) and on positivity of the culture further confirmed by qPCR.

Conclusions

Since last few decades, among the eight reviewed patients, H. capsulatum sinusitis occurred mostly in HIV-immunocompromised patients and for three cases as a sinusitis with disseminated histoplasmosis. Even if this is a rare clinical presentation, its diagnosis is crucial as it could represent an early expression of an Histoplasma capsulatum exposure that can evolve into a disseminated fatal infection when immunity decreases.

Molecular detection of Histoplasma capsulatum in insectivorous and frugivorous bats in Southeastern Brazil

Bats are considered to play a significant role in the epidemiology of histoplasmosis, worldwide. We investigated the occurrence of H. capsulatum in lung samples from 89 bats, from urban areas in Southeastern Brazil, using nested PCR based on ribosomal DNA. Fungal DNA was detected in 31/89 samples (34.8%), of which 13/31 were Molossids (41.9%), 4/31 Eumops spp. (12.9%), 2/31 Artibeus lituratus (6.5%), and 12/31 others (38.7%). This is the first report of natural infection by H. capsulatum in A. lituratus in Southeastern Brazil, which reinforces the importance of these synanthropic animals in the epidemiology of histoplasmosis in urban areas.

Fungal infections in pediatric neurosurgery

INTRODUCTION

Invasive mycosis of the central nervous system represent a diverse group of diseases that have gradually emerged as not only opportunistic infections in patients with immune susceptibility due to congenital and acquired deficiency, immunomodulation, solid organ and stem cell transplantation, hematological malignancies, and chronic steroid use but also in selected risk populations such as low weight preterm infants, patients with shunted hydrocephalus and external ventricular drainages, skull base surgery, and head injury.

OBJECTIVES

The purpose of this review is to familiarize the pediatric neurosurgeon with the most common mycosis and their clinical scenarios which can be encountered in the clinical practice, with special emphasis on clinical, radiological, and laboratory diagnosis beyond classical microorganism cultures as well as options in medical and surgical treatment given the high incidence of morbidity and mortality associated with these challenging entities.

METHODS

We conducted an online database review (Ovid, PubMed) gathering relevant English language literature published in the last 20 years with special emphasis on recent breakthroughs in the diagnosis and treatment of invasive mycosis of the CNS as well as reported cases within the pediatric neurosurgical literature and their surgical management.

RESULTS

Fungal agents capable of invading the CNS can behave as aggressive entities with rapid progression manifesting as overwhelming meningoencephalitis with vascular compromise or can lead to space-occupying lesions with abscess formation which require prompt diagnosis by either laboratory identification of the components of these biological agents and their host response or by obtaining tissue specimens for microbiological identification which may not be straightforward due to prolonged culture time.

CONCLUSION

Following a high degree of suspicion with prompt initiation of antifungal agents and reversal of potential immunosuppressant therapies along with neurosurgical evacuation of intracranial collections or removal of infected hardware (CSF shunts) can lead to more optimistic outcomes of these complex clinical scenarios.

Candidate prognostic indicators in cats with histoplasmosis treated with antifungal therapy

Objectives The aim of this study was to retrospectively identify candidate prognostic indicators in cats with histoplasmosis treated with antifungal therapy. Methods Medical records of cats diagnosed with histoplasmosis were reviewed. Candidate prognostic indicators were assessed for an association with survival to hospital discharge and survival to 1 and 6 months after diagnosis. Potential indicators included easily obtained data at the time of the initial hospital visit derived from cat signalment, historical information, physical examination, laboratory data, form of disease and initial treatment. Results Approximately 88% of cats survived to discharge, with 77% and 67% surviving to 1 and 6 months, respectively. Clinical variables significantly associated with death at more than one outcome time point included the presence of dyspnea, adventitial lung sounds, fungemia, neurologic disease, neutropenia, lymphopenia, multiple cytopenias (anemia, neutropenia, thrombocytopenia), hyperbilirubinemia and increased creatinine kinase activity. Cats that did not survive were more likely to have received corticosteroids, oxygen supplementation and required hospitalization. In addition, cats that did not survive required significantly longer hospitalization. There was no significant difference between initial antifungal drug and survival. Conclusions and relevance Potential prognostic indicators were associated with more severe respiratory, hepatic, hematologic or neurologic disease. Prospective investigation concerning clinical indicators of disease severity of these body systems is indicated.

Predictive factors for disseminated histoplasmosis in AIDS patients with fever admitted to a reference hospital in Brazil

INTRODUCTION

In many settings, the lack of sensitive biomarkers of disseminated histoplasmosis (DH) leads to a clinical reliance on older diagnostic methods and delayed treatment initiation. The early recognition of DH is critical for survival, especially in patients with human immunodeficiency virus (HIV). This study aimed to identify clinical and laboratory findings associated with the definitive diagnosis of DH in low-income HIV patients in endemic areas.

METHODS

Febrile AIDS patients with suspected DH who were admitted to a reference hospital in northeastern Brazil from January 2006 to January 2007 were evaluated for clinical and laboratory findings associated with DH diagnosis.

RESULTS

One hundred seventeen patients with fever were included, and 48 (41%) cases of DH were determined by Histoplasma capsulatum identification. A higher fever (≥38.5ºC), maculopapular/papular rash, splenomegaly, hepatomegaly, wheezing, hemoglobin ≤9.5g/dL, platelets ≤80,000/µL, CD4 count ≤75/µL, aspartate aminotransferase (AST) level ≥2.5 times the upper limit of normal (ULN), lactate dehydrogenase (LDH) ≥5times the ULN; and international normalized ratio (INR) >2 times the ULN were significantly associated with DH. A multivariable analysis identified hepatomegaly [adjusted (a) prevalence ratio (PR)= 1.96; 95% confidence interval (CI): 1.21-3.16), CD4 count ≤75/µL (aPR = 2.02; 95% CI: 1.06-3.83), LDH ≥5 times the ULN (aPR = 2.23; 95% CI: 1.44-3.48), and maculopapular/papular rash (aPR = 1.70; 95% CI: 1.02-2.83) were independent risk factors for DH.

CONCLUSIONS

These easily assessed parameters can facilitate clinical decision-making for febrile AIDS patients with suspected DH in low socioeconomic and Histoplasma-endemic regions.

Burden of HIV-associated histoplasmosis compared with tuberculosis in Latin America: a modelling study

BACKGROUND

Fungal infections remain a major contributor to the opportunistic infections that affect people living with HIV. Among them, histoplasmosis is considered neglected, often being misdiagnosed as tuberculosis, and is responsible for numerous deaths in Latin America. The objective of this study was to estimate the burden of HIV-associated histoplasmosis compared with tuberculosis in Latin American countries.

METHODS

For this modelling study, we estimated prevalence of previous exposure to Histoplasma capsulatum, HIV-associated histoplasmosis annual incidence, and number of deaths in 2012 in Latin American countries based on historical histoplasmin skin test studies in the general population, with an antigen dilution level of more than 1/10. Studies were identified in a literature search. Data on HIV-associated tuberculosis were extracted from the WHO notifications and outcomes tables and data on people living with HIV were extracted from the UNAIDS report for the year 2012. We systematically propagated uncertainty throughout all the steps of the estimation process.

FINDINGS

Among 1310 articles identified as of June 1, 2015, 24 articles were included in the study, representing 129 histoplasmin skin test studies led in the general population of Latin American countries. For the year 2012, we estimated a range of 6710 (95% CI 5680-7867) to 15 657 (13 254-18 357) cases of symptomatic HIV-associated histoplasmosis in Latin America. Hotspot areas for histoplasmosis prevalence (>30%) and incidence (>1·5 cases per 100 people living with HIV) were Central America, the northernmost part of South America, and Argentina. According to realistic scenarios, we estimated a range of 671 (95% CI 568-787) to 9394 (7952-11 014) deaths related to histoplasmosis, compared with 5062 (3777-6405) deaths related to tuberculosis reported in Latin America.

INTERPRETATION

Our estimates of histoplasmosis incidence and deaths are high and consistent with published data. For the first time, the burden of histoplasmosis is estimated to be equivalent in incidence and even higher in deaths when compared with tuberculosis among people living with HIV in Latin America.

FUNDING

None.

African histoplasmosis: new clinical and microbiological insights

African histoplasmosis is defined as the fungal infection caused by Histoplasma capsulatum var. duboisii (Hcd). Studies focused on distinguishing Hcd and H. capsulatum var. capsulatum (Hcc), which coexist in Africa, are scarce or outdated, and African strains are continuously underrepresented. In this work, 13 cases of African patients with histoplasmosis diagnosed in the Spanish Mycology Reference Laboratory have been reviewed showing that 77% had disseminated disease and AIDS as underlying disease although Hcd infection has been classically considered a rare presentation in AIDS patients. Strains isolated from these patients and other clinical and reference strains were studied by assessing classical identification methods and performing a three-loci multi-locus sequence analysis (MLSA). Classical identification methods based on biochemical tests and measurement of yeast size proved to be useless in distinguishing both varieties. The MLSA defined an African cluster, with a strong statistical support, that included all strains with African origin. Finally, mating type was also determined by using molecular methods revealing an unequal mating type distribution in African strains. In conclusion, historical statements and classical identification methods were useless to distinguish between varieties, whereas molecular analyses revealed that all strains with African origin grouped together suggesting that traditional classification should be revised. Further investigation is required in order to unravel traditional concepts about Hcd infection and support results obtained in this work.

A 44-year-old man with hemoptysis

A 44-year-old man with background history of diffuse cutaneous systemic sclerosis and dilated cardiomyopathy receiving immunosuppressive medications, presented with a 2-month history of cough and streaky hemoptysis. Clinicoradiological features were consistent with an endotracheal mass. Subsequently, the patient developed nodular skin lesions and the tracheal mass increased in size causing central airway obstruction. This clinicopathologic conference discusses the clinical and radiological differential diagnoses of such a clinical presentation and their management options.

AST to ALT Ratio is elevated in disseminated histoplasmosis as compared to localized pulmonary disease and other endemic mycoses

Severe pulmonary or disseminated histoplasmosis often necessitates presumptive antifungal treatment while awaiting definitive diagnosis. Histoplasma antigen assays have improved sensitivity but results may lag up to 7 days. In order to increase diagnostic certainty, "soft clues" may be looked for in laboratory and radiologic data, such as elevated alkaline phosphatase or ferritin levels and findings of mediastinal adenopathy or hepatosplenomegaly. To determine if elevated aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio is specific to histoplasmosis or a non-specific marker for disseminated fungal infection or sepsis in general, we retrospectively examined records of all patients diagnosed with an endemic fungal infection (EFI) at Rush University Medical Center from January of 1997 to October of 2012, and a cohort of septic patients with elevated liver enzymes. We identified 90 cases of EFIs during the study period that met all inclusion criteria (Histoplasma 21, Blastomyces 56, Coccidioides 12, Paracoccidioides 1). We also evaluated 10 control patients with bacterial sepsis. The mean ratio of AST to ALT in patients with disseminated histoplasmosis was 2.69 (95% CI:1.22, 4.16) while for other EFIs, the mean ratio ranged from 0.38 to 1.14 with disseminated coccidioidomycosis and blastomycosis respectively (P < 0.0001). The ratio in patients with bacterial sepsis was 0.84. We propose the use of the AST/ALT ratio as a clinical "soft clue" suggestive of disseminated histoplasmosis in the appropriate host, and to possibly distinguish cross reactivity of the Histoplasma antigen assay with other EFIs.

Disseminated Histoplasmosis as AIDS-presentation. Case Report and Comprehensive Review of Current Literature

Progressive disseminated histoplasmosis (PDH) is an AIDS-defining illness with a high lethality rate if not promptly treated. The wide range of its possible clinical manifestations represents the main barrier to diagnosis in non-endemic countries. Here we present a case of PDH with haemophagocytic syndrome in a newly diagnosed HIV patient and a comprehensive review of disseminated histoplasmosis focused on epidemiology, clinical features, diagnostic tools and treatment options in HIV-infected patients.

Recent admixture between species of the fungal pathogen Histoplasma

Hybridization between species of pathogens has the potential to speed evolution of virulence by providing the raw material for adaptation through introgression or by assembling new combinations of virulence traits. Fungal diseases are a source high morbidity, and remain difficult to treat. Yet the frequency of hybridization between fungal species has rarely been explored, and the functional role of introgressed alleles remains largely unknown. Histoplasma mississippiense and H. ohiense are sympatric throughout their range in North America and have distinct virulence strategies, making them an ideal system to examine the role introgression may play in fungal pathogens. We identified introgressed tracts in the genomes of a sample of H. mississippiense and H. ohiense isolates. We found strong evidence in each species for recent admixture, but introgressed alleles were present at low frequencies, suggesting that they were deleterious. Consistent with this, coding and regulatory sequences were strongly depleted within introgressed regions, whereas intergenic regions were enriched, indicating that functional introgressed alleles were frequently deleterious in their new genomic context. Surprisingly, we found only two isolates with substantial admixture: the H. mississippiense and H. ohiense genomic reference strains, WU24 and G217B, respectively. Our results show that recent admixture has occurred, that it is frequently deleterious and that conclusions based on studies of the H. mississippiense and H. ohiense type strains should be revisited with more representative samples from the genus.

Miliary Histoplasmosis in a Patient with Rheumatoid Arthritis

Miliary histoplasmosis is a rare presentation that may mimic miliary tuberculosis. We report a case of miliary histoplasmosis in a 52-year-old male who was being treated with hydroxychloroquine, methotrexate, and sulfasalazine for his rheumatoid arthritis and presented to the emergency department with shortness of breath and fevers. Computed tomography (CT) chest revealed miliary pulmonary nodules. Urine Histoplasma antigen and serum Histoplasma antigen were negative; however, Coccidioides immitis complement immunofixation assay and Coccidioides IgM were positive. The patient was initiated on treatment for pulmonary coccidioidomycosis and immunosuppression was held. However, a few days later, Histoplasma capsulatum was isolated from cultures from bronchoscopy. This case highlights the difficulty in diagnosing histoplasmosis in immunocompromised patients and the importance of having a broad differential diagnosis for miliary pulmonary nodules. Tissue culture and histopathology remain the gold standard for the diagnosis of histoplasmosis. Further research needs to be conducted to determine the optimal duration of histoplasmosis treatment in immunocompromised patients.

Adrenal Histoplasmosis

An 89-year-old woman presented with seizure and hyponatremia. CT and MRI demonstrated mass-like enlargement of the adrenal glands and multiple pulmonary nodules. PET/CT performed to evaluate for metastatic disease demonstrated intense F-FDG uptake within enlarged adrenal glands. Given mild uptake in the pulmonary nodules, the differential diagnosis for the adrenal uptake included lymphoma, granulomatous infection, and less likely, metastatic lung cancer.

Updates in the Language of Histoplasma Biodiversity

In a recent article, Sepúlveda et al. (mBio 8:e01339-17, 2017, https://doi.org/10.1128/mBio.01339-17) investigated the genetic structure and evolutionary history of the human pathogen Histoplasma. Using whole-genome resequencing data, Sepúlveda et al. found that the Histoplasma genus is composed of at least four strongly differentiated lineages. Their tour de force is to use a smart combination of population genomic approaches to show that the advanced stage of intraspecific divergence observed within Histoplasma does not simply reflect population structure, but instead results from previously unidentified speciation events. The four independently evolving Histoplasma lineages are elevated to the species status and assigned names. The newly described species exhibit medically important differences in phenotype, and these findings, therefore, have important epidemiological implications. This work provides a blueprint for phylogenomic species recognition in fungi, opening the way for a new age of enlightenment in which fungal species are diagnosed using highly discriminatory tools within a hypothesis-testing framework.

Out of town guest: A healthy 7 year old from a non-endemic area presents with histoplasmosis granulomatous disease

Histoplasmosis is a common fungal infection, normally infecting people exposed to demolition sites or bat/bird droppings in the central and eastern states. When a child presents with a chest mass and eosinophilia in a non-endemic region the likelihood of an infectious process like pulmonary histoplasmosis is unknown. A seven year old immunocompetent child with a mediastinal mass and eosinophilia presented with acute cough, fever, non-bloody emesis, and four pound weight loss. A neoplastic work up was negative. Further evaluation showed a positive M band (chronic histoplasmosis infection) and negative H band (acute infection). Tissue obtained by thoracotomy demonstrated necrotizing granulomatous inflammation with calcification consistent with histoplasmosis. Patient recovered after completion of a twelve week course of itraconazole. A mediastinal mass in a symptomatic child has a 50% risk of cancer as the primary diagnosis. The Infectious Disease Society of America guidelines recommend treatment of histoplasmosis granulomatous disease with itraconazole if symptomatic and surgery only for obstruction. Thus our patient did not have a clear indication for surgery. In a child with a mediastinal mass, despite low risk factors should they be evaluated for a fungal infection prior to invasive surgery? This case demonstrates that histoplasmosis can cause a granuloma in a non-endemic region and that an infectious etiology ought to be considered when working up a symptomatic child with a chest mass as it may prevent unnecessary surgery.

Prevalence and echo features of mediastinal lymph nodes in EUS for non-malignant indications: a prospective study in a Southern European Population

BACKGROUND AND STUDY AIMS

 Significant heterogeneity in geographic distribution regarding the prevalence of mediastinal lymph nodes (MLN) has been documented in autopsy and computed tomography (CT) studies. Awareness of the local prevalence and characteristics of lymph nodes will be relevant when performing endoscopic ultrasonography (EUS) for staging of malignant neoplasias. The aims of this study were to document the prevalence and echo features of MLN in patients undergoing EUS for non-malignant extrathoracic disease and to identify predictive factors for the presence of MLN.

PATIENTS AND METHODS

 A prospective single-center study was performed over 6 months. Mediastinal stations 9, 8, 7, 6, 5, 4 L and 2 were systematically evaluated using a linear echoendoscope in all patients undergoing EUS due to benign extrathoracic pathology and without history of oncologic disease. Demographic, clinical and EUS features of the lymph nodes were analysed.

RESULTS

 Seventy-five patients were included: male/female 32/43; mean age, 63 years. The majority of patients (72 %) had lymph nodes in at least one mediastinal station and 88 % of these were found in stations 7 or 4 L. Overall, 133 MLN were identified: 19 % were hypoechogenic, 6 % had a short-axis diameter > 10 mm, and 6 % were round. The prevalence of lymph nodes was higher in smokers (83 % vs 64 %, P  = 0.024), with a higher average number of lymph nodes per patient in this group (2.1 vs 1.6; P  = 0.017). By logistic regression analysis, none of the variables analyzed were independently associated with the presence of MLN.

CONCLUSION

 This prospective Portuguese study documented a higher prevalence of MLN than previously reported in Northern Europe, in patients with no evidence of oncologic disease. This higher prevalence may negatively influence the specificity and positive predictive value for malignancy of MLN (N) staging by EUS.

Histoplasma Urinary Antigen Testing Obviates the Need for Coincident Serum Antigen Testing

OBJECTIVES

Serum and urine antigen (SAg, UAg) detection are common tests for Histoplasma capsulatum. UAg detection is more widely used and reportedly has a higher sensitivity. We investigated whether SAg detection contributes meaningfully to the initial evaluation of patients with suspected histoplasmosis.

METHODS

We reviewed 20,285 UAg and 1,426 SAg tests ordered from 1997 to 2016 and analyzed paired UAg and SAg tests completed on the same patient within 1 week. We determined the positivity rate for each test.

RESULTS

Of 601 paired specimens, 542 were concurrent negatives and 48 were concurrent positives (98% agreement). Medical records were available for eight of 11 pairs with discrepant results. UAg was falsely positive in six instances, truly positive once, and falsely negative once.

CONCLUSIONS

These findings support using a single antigen detection test, rather than both UAg and SAg, as an initial screen for suspected histoplasmosis. This aligns with the current practice of most physicians.

Disseminated histoplasmosis diagnosed in the bone marrow of an HIV-infected patient: First case imported in Tunisia

Histoplasmosis is a fungal infection caused by a dimorphic fungus, Histoplasma capsulatum. We report a first case of disseminated histoplasmosis in a 34-year-old woman, infected with human immunodeficiency virus (HIV), originating from Ivory Coast and living in Tunisia for 4 years. She was complaining from fever, chronic diarrhoea and pancytopenia. The Histoplasma capsulatum var. capsulatum was identified by direct microscopic examination of the bone marrow. She was treated by Amphotericin B, relayed by itraconazole. Even though a regression of symptoms and normalization of blood cell count (BCC), the patient died in a respiratory distress related to CMV hypoxemic pneumonia.

Advances in the diagnosis and treatment of fungal infections of the CNS

Fungal infections of the CNS are challenging to treat and their optimal management requires knowledge of their epidemiology, host characteristics, diagnostic criteria, and therapeutic options. Aspergillus and Cryptococcus species predominate among fungal infections of the CNS. Most of these fungi are ubiquitous, but some have restricted geographical distribution. Fungal infections of the CNS usually originate from primary sites outside the CNS (eg, fungal pneumonia) or occur after inoculation (eg, invasive procedures). Most patients with these infections have immunodeficiencies, but immunocompetent individuals can also be infected through heavy exposure. The infecting fungi can be grouped into moulds, yeasts, and dimorphic fungi. Substantial progress has been made with new diagnostic approaches and the introduction of novel antifungal drugs, but fungal infections of the CNS are frequently lethal because of diagnostic delays, impaired drug penetration, resistance to antifungal treatments, and inadequate restoration of immune function. To improve outcomes, future research should advance diagnostic methods (eg, molecular detection and fungus identification), develop antifungal compounds with enhanced CNS-directed efficacy, and further investigate crucial host defence mechanisms.

Challenges in the Diagnosis of Invasive Fungal Infections in Immunocompromised Hosts

Purpose of review

The expanding population of immunocompromised patients coupled with the recognition of a growing number of different species of fungi responsible for diseases in such hosts makes the diagnosis of invasive fungal infection (IFI) a challenging task. The recent advances and challenges in the diagnosis of IFI in the setting of immunocompromised hosts are reviewed. The advantages and limitations of histopathology and the role of culture-independent methods, such as those based on the use of nucleic acids applied to fresh and formalin-fixed, paraffin-embedded sections, besides culture- and non-culture-based diagnostic methods, to obtain a timely and correct diagnosis of IFI are highlighted.

Recent findings

The therapeutic implications of identifying the genus and species of the fungus present in the specimen with the molecular diagnostics applied to tissue specimens are reviewed. No method alone is efficient in correctly identifying fungi and it is essential to combine the traditional histochemical staining with molecular methods to achieve a rapid and genus-/species-specific diagnosis of IFI.

Summary

We review the recent findings and challenges in the hystopathologic diagnosis of IFI in the setting of immunocompromised hosts. Non method alone is efficient in correctly identify fungi and pathologists should combine classic staining with molecular methods to achieve a rapid and genus/species fungal diagnosis.

Comparison of diagnostic methods to detect Histoplasma capsulatum in serum and blood samples from AIDS patients

BACKGROUND

Although early and rapid detection of histoplasmosis is essential to prevent morbidity and mortality, few diagnostic tools are available in resource-limited areas, especially where it is endemic and HIV/AIDS is also epidemic. Thus, we compared conventional and molecular methods to detect Histoplasma capsulatum in sera and blood from HIV/AIDS patients.

METHODOLOGY

We collected a total of 40 samples from control volunteers and patients suspected of histoplasmosis, some of whom were also infected with other pathogens. Samples were then analyzed by mycological, serological, and molecular methods, and stratified as histoplasmostic with (group I) or without AIDS (group II), uninfected (group III), and infected with HIV and other pathogens only (group IV). All patients were receiving treatment for histoplasmosis and other infections at the time of sample collection.

RESULTS

Comparison of conventional methods with nested PCR using primers against H. capsulatum 18S rRNA (HC18S), 5.8S rRNA ITS (HC5.8S-ITS), and a 100 kDa protein (HC100) revealed that sensitivity against sera was highest for PCR with HC5.8S-ITS, followed by immunoblotting, double immunodiffusion, PCR with HC18S, and PCR with HC100. Specificity was equally high for double immunodiffusion, immunoblotting and PCR with HC100, followed for PCR with HC18S and HC5.8-ITS. Against blood, sensitivity was highest for PCR with HC5.8S-ITS, followed by PCR with HC18S, Giemsa staining, and PCR with HC100. Specificity was highest for Giemsa staining and PCR with HC100, followed by PCR with HC18S and HC5.8S-ITS. PCR was less efficient in patients with immunodeficiency due to HIV/AIDS and/or related diseases.

CONCLUSION

Molecular techniques may detect histoplasmosis even in cases with negative serology and mycology, potentially enabling early diagnosis.

Lung Infections

A review of pulmonary infections of all types with diagnostic and morphological features.