Histoplasmosis: Epidemiology, Diagnosis, and Clinical Manifestations

Practical Guidance for Clinical Microbiology Laboratories: Antibody and antigen detection methods for dimorphic fungal infections

SUMMARYAntibody and antigen detection assays continue to play a significant role in the diagnosis of dimorphic fungal pathogens, including Blastomyces dermatitidis complex, Coccidioides immitis/posadasii, Paracoccidioides species, Histoplasma species, Sporothrix species, and Talaromyces marneffei. The performance characteristics of serologic and antigen detection assays for these pathogens are variable, however, influenced by multiple factors, including sample type, disease presentation, patient immunostatus, and timing of specimen collection relative to symptom onset. As a result, there is a need for a centralized document summarizing the accuracy of currently available antibody and antigen detection assays for each of these agents, including discussion of individual assay nuances and caveats that should be considered by clinicians and laboratorians alike. In addition, this review provides expert recommendations for the utilization and interpretation of serologic and antigen detection assays for these dimorphic pathogens.

Left Recurrent Laryngeal Nerve Vocal Fold Paralysis in Pediatric Patient Secondary to Mediastinal Histoplasmosis Infection

Histoplasma capsulatum is a dimorphic soil-based fungus endemic to the Ohio and Mississippi River valleys and southeastern United States. An extremely rare presentation is the involvement of the mediastinum leading to vocal fold paralysis, with only 2 reported cases in the literature. This report presents the youngest patient to whom this pathology has been described and the third overall patient. In this case report, we present a 15-year-old boy with vocal fold paralysis secondary to left recurrent laryngeal nerve paralysis in the setting of confirmed histoplasmosis infection. On further workup, he was noted to have mediastinum lymphadenopathy on computed tomography (CT) chest. Pathology of the biopsy indicated granulomatous inflammation without the evidence of malignancy, prompting fungal serology testing resulting in a positive histoplasma antibody result. The patient received appropriate treatment, yet the dysphonia persisted. On flexible laryngoscopy, he was noted to have left vocal fold paralysis. After 2 years of ongoing paralysis, the decision was made to proceed with recurrent laryngeal nerve innervation for long-term benefits. After nerve innervation and fat laryngoplasty, the patient has had significant improvement in dysphonia and voice parameters.

Detection of Histoplasma capsulatum in Bats from the Brazilian Western Amazon

Histoplasma capsulatum is a saprophytic dimorphic fungus that causes histoplasmosis, a systemic infectious disease of relevance to public health. Bats can be important agents in the epidemiological cycle of the disease since they act as reservoirs of microorganisms. The aim of this study was to detect Histoplasma capsulatum in the lung tissue of bats captured in urban forest fragments in the municipality of Rio Branco, Acre, in the Western Amazon. Twenty-two bat species were captured from five urban forest fragments. The samples taken were subjected to histopathological, mycological, and molecular analysis. Among the 96 animals analyzed, the fungus was detected in 32.29% (31/96). This was the first study to detect the pathogen in bats in the Western Amazon. It is also the first record of the fungus being detected in six bat species. The state of Acre is located in a region with a rich diversity of bats. Furthermore, this area is constantly suffering from climatic and environmental changes that can favor the emergence and re-emergence of diseases. Thus, active epidemiological research and surveillance of neglected fungal infections are essential, especially considering the concept of One Health.

Progressive Severe Hemophagocytic Syndrome due to Disseminated Histoplasmosis in a Patient with HIV-1 Infection

Histoplasmosis is caused by Histoplasma capsulatum and is prevalent in areas of the world where H. capsulatum is endemic. We herein report a patient diagnosed with human immunodeficiency virus-1 (HIV-1) who developed histoplasmosis from a non-H. capsulatum endemic area who experienced severe hemophagocytic syndrome due to a delayed diagnosis. The patient's symptoms emerged four years after residing in regions with a high histoplasmosis prevalence. The unrestricted administration of antifungal medication for oral candidiasis delayed the diagnosis because it improved the patient's condition. This case underscores the importance of prudent antifungal drug use in undiagnosed disseminated conditions and evaluating the travel history going back several years to facilitate a diagnosis.

Mapping Histoplasma in Bats and Cave Ecosystems: Evidence from Midwestern Brazil

Caves serve as natural reservoirs for diverse microbial species due to their unique biotic and abiotic conditions. Histoplasma spp. is frequently associated with guano-enriched soil, low luminosity, and high humidity, particularly in Latin America, a region highly endemic for histoplasmosis. Despite the continent's diverse biomes, local environmental and host distributions of Histoplasma remain poorly understood. To address this knowledge gap, we conducted a Histoplasma -specific quantitative PCR (qPCR) assay targeting the hc100 gene on guano samples from seven bat-inhabited caves and tissue samples from 74 bats of nine species in the Federal District of Brazil and surround-ing regions. We detected Histoplasma DNA in 16 of 80 soil samples (20%) and in 33 bats representing seven species. Among 222 tissue samples (74 lung, 74 spleen, 74 brain), 39 tested positive: 22 lung, 10 spleen, and 7 brain samples. Four bats had Histoplasma DNA in both lung and brain, and two in both lung and spleen. By mapping the presence of Histoplasma across sampled caves, we identified environmental hotspots of fungal prevalence, emphasizing the need for targeted surveillance.

Importance

Our study provides critical insights into the environmental and host distribution of Histoplasma spp. in Brazil, identifying caves with high fungal prevalence and demonstrating its presence in multiple bat species. These findings underscore the necessity of public health interventions to mitigate the risk of histoplasmosis among cave visitors in the region. Additionally, we highlight the utility of qPCR for detecting Histoplasma in environmental and biological samples, supporting future epidemiological research in Latin America.

Bilateral Adrenal Nodules in the Setting of Disseminated Fungal Infection: An Important Consideration for Appropriate Management of Adrenal Pathology

Background/Objective

Increased utilization of cross-sectional imaging has led to a rise in diagnosis of incidental adrenal lesions. Physicians in many clinical settings are increasingly faced with addressing these incidental lesions by initiating the correct workup, diagnosis, and long-term follow-up plan. Our objective was to demonstrate the importance of maintaining a broad differential and completing a thorough workup in determining the correct treatment plan for patients with bilateral adrenal lesions.

Case Report

We present 2 patients who recently completed chemotherapy for lymphoma, found to have new bilateral adrenal lesions on postchemotherapy imaging. Urine antigen and/or adrenal biopsy was performed to confirm the diagnosis of disseminated fungal infection. This diagnosis has major implications on the treatment plan, which includes antifungal therapy instead of surgical management or additional chemotherapy. Cross-sectional imaging after initiation of antifungal treatment demonstrated decreasing size of nodules.

Discussion

A broad differential is critical when working up and developing treatment plans for adrenal nodules, specifically considering a fungal etiology in the setting of immunosuppression or primary extra-adrenal malignancy.

Conclusion

Incidentally found adrenal lesions are becoming more common, and in turn, the obligation for appropriate management of adrenal pathology not only falls to medical and surgical endocrinologists but also to general practitioners. It is prudent to consider atypical etiologies including disseminated fungal infection prior to surgical excision or initiation of chemotherapy as those treatment strategies would not benefit select patients.

Gastric Outlet Obstruction Caused by Histoplasmosis in a Nonendemic Region

Histoplasmosis capsulatum is a dimorphic fungus commonly considered endemic in the Mississippi and Ohio River Valley regions. Histoplasmosis can present as asymptomatic in immunocompetent patients or present as a disseminated infection in immunocompromised patients. Diagnosing histoplasmosis can be challenging in nonendemic areas, especially in patients presenting primarily with gastrointestinal symptoms. We describe a case of an immunocompromised 29-year-old man presenting with gastric outlet obstruction caused by disseminated histoplasmosis in a region not commonly considered endemic to Histoplasmosis capsulatum.

Disseminated Histoplasmosis as a Presentation of Advanced HIV-1 Infection in a Non-endemic Country

Disseminated histoplasmosis is an opportunistic fungal infection considered an AIDS-defining illness, sometimes with a fatal outcome. We report a case of disseminated histoplasmosis as the initial presentation of advanced HIV-1 infection in a migrant living in a non-endemic area. Histoplasmosis was suspected based on the clinical presentation, epidemiological factors, and observation in the peripheral blood smear of neutrophils and monocytes with yeast-like forms. The diagnosis was confirmed through a positive peripheral blood smear and subsequent culture of Histoplasma capsulatum from a bronchoalveolar lavage sample. The patient was treated with 14 days of liposomal amphotericin B plus oral itraconazole for two years, with a good response. Direct examination of peripheral blood has been considered a valuable diagnostic method, specifically in severely immunocompromised patients, as our case report. The presented case highlights the importance of considering disseminated histoplasmosis in the differential diagnosis of HIV-infected patients, even in non-endemic regions. Hence, the need for a high index of suspicion to ensure early diagnosis and treatment is crucial as the influx of migrants increases globally.

Tracing histoplasmosis genomic epidemiology and species occurrence across the USA

ABSTRACTHistoplasmosis is an endemic mycosis in North America frequently reported along the Ohio and Mississippi River Valleys, although autochthonous cases occur in non-endemic areas. In the United States, the disease is provoked by two genetically distinct clades of Histoplasma capsulatum sensu lato, Histoplasma mississippiense (Nam1) and H. ohiense (Nam2). To bridge the molecular epidemiological gap, we genotyped 93 Histoplasma isolates (62 novel genomes) including clinical, environmental, and veterinarian samples from a broader geographical range by whole-genome sequencing, followed by evolutionary and species niche modelling analyses. We show that histoplasmosis is caused by two major lineages, H. ohiense and H. mississippiense; with sporadic cases caused by H. suramericanum in California and Texas. While H. ohiense is prevalent in eastern states, H. mississipiense was found to be prevalent in the central and western portions of the United States, but also geographically overlapping in some areas suggesting that these species might co-occur. Species Niche Modelling revealed that H. ohiense thrives in places with warmer and drier conditions, while H. mississippiense is endemic to areas with cooler temperatures and more precipitation. In addition, we predicted multiple areas of secondary contact zones where the two species co-occur, potentially facilitating gene exchange and hybridization. This study provides the most comprehensive understanding of the genomic epidemiology of histoplasmosis in the USA and lays a blueprint for the study of invasive fungal diseases.

Associations between Minority Health Social Vulnerability Index Scores, Rurality, and Histoplasmosis Incidence, 8 US States

To explore associations between histoplasmosis and race and ethnicity, socioeconomic status, and rurality, we conducted an in-depth analysis of social determinants of health and histoplasmosis in 8 US states. Using the Minority Health Social Vulnerability Index (MH SVI), we analyzed county-level histoplasmosis incidence (cases/100,000 population) from the 8 states by applying generalized linear mixed hurdle models. We found that histoplasmosis incidence was higher in counties with limited healthcare infrastructure and access as measured by the MH SVI and in more rural counties. Other social determinants of health measured by the MH SVI tool either were not significantly or were inconsistently associated with histoplasmosis incidence. Increased awareness of histoplasmosis, more accessible diagnostic tests, and investment in rural health services could address histoplasmosis-related health disparities.

Diagnosis of Human Endemic Mycoses Caused by Thermally Dimorphic Fungi: From Classical to Molecular Methods

Human endemic mycoses are potentially fatal diseases caused by a diverse group of fungi that can alter their morphology in response to an increase in temperature. These thermally dimorphic fungi affect both healthy and immunocompromised hosts, causing a substantial health and economic burden. Despite this, the diagnosis of endemic mycoses is still a formidable challenge for several reasons, including similar symptomatology, limited utility of classical diagnostic methods, inaccessibility to reliable molecular approaches in most endemic areas, and a lack of clinical suspicion out of these regions. This review summarizes essential knowledge on thermally dimorphic fungi and the life-threatening diseases they cause. The principle, advantages and limitations of the methods traditionally used for their diagnosis are also described, along with the application status and future directions for the development of alternative diagnostic strategies, which could help to reduce the disease burden in endemic areas.

The Association of Chronic Pulmonary Aspergillosis and Chronic Pulmonary Histoplasmosis with MDR-TB Patients in Indonesia

In Indonesia, 2.4% of all new tuberculosis patients had multi-drug resistant disease (MDR-TB); an estimated 24,000 incidences. Historical case series of MDR-TB described a high frequency of cavitation and poor prognosis. The diagnosis of chronic pulmonary aspergillosis (CPA) relies on raised levels of Aspergillus IgG antibodies, and detectable Histoplasma IgG antibodies are suspicious for chronic pulmonary histoplasmosis (CPH). We investigated whether MDR-TB patients might have concurrent CPH or CPA. This was a cross-sectional study with 50 MDR-TB patients. ELISA was used to detect Histoplasma IgG antibodies and lateral flow assay was used to detect Aspergillus IgG/IgM antibodies. Several other possible disease determinants were assessed by multivariate analysis. Of the 50 MDR-TB patients, 14 (28%) and 16 (32%) had positive Histoplasma or Aspergillus serology; six patients (12%) had dual antibody reactivity. Radiological abnormalities in positive patients included diffuse or local infiltrates, nodules, consolidation, and apical cavities, consistent with CPH and CPA. Patients with detectable fungal antibodies tended to have worse disease, and 4 of 26 (15.3%) died in the first 5 months of dual infection (p = 0.11 compared with no deaths in those with only MDR-TB). The criteria for the diagnosis of CPH and CPA were fulfilled in those with moderately and far advanced disease (13 of 14 or 93%) and 12 of 16 (75%), respectively. Damp housing was the only determinant associated with Histoplasma antibodies (PR 2.01; 95%CI 0.56-7.19), while pets were associated with the Aspergillus antibody (PR 18.024; 95%CI 1.594-203.744). CPA or CPH are probably frequent in MDR-TB patients in Indonesia and may carry a worse prognosis.

Genotypic diversity, virulence, and molecular genetic tools in Histoplasma

SUMMARYHistoplasmosis is arguably the most common fungal respiratory infection worldwide, with hundreds of thousands of new infections occurring annually in the United States alone. The infection can progress in the lung or disseminate to visceral organs and can be difficult to treat with antifungal drugs. Histoplasma, the causative agent of the disease, is a pathogenic fungus that causes life-threatening lung infections and is globally distributed. The fungus has the ability to germinate from conidia into either hyphal (mold) or yeast form, depending on the environmental temperature. This transition also regulates virulence. Histoplasma and histoplasmosis have been classified as being of emergent importance, and in 2022, the World Health Organization included Histoplasma as 1 of the 19 most concerning human fungal pathogens. In this review, we synthesize the current understanding of the ecological niche, evolutionary history, and virulence strategies of Histoplasma. We also describe general patterns of the symptomatology and epidemiology of histoplasmosis. We underscore areas where research is sorely needed and highlight research avenues that have been productive.

Clinical characteristics, diagnosis, treatment and outcomes of patients living with HIV and co-infected with tuberculosis and histoplasmosis: a 5-y retrospective case series

BACKGROUND

In Latin America, tuberculosis (TB) and histoplasmosis are two of the most frequent opportunistic infections affecting people living with human immunodeficiency virus (HIV). However, there are limited data on the clinical characteristics and outcomes of patients with concurrent TB and histoplasmosis infections.

METHODS

This was a retrospective observational study to describe the clinical, epidemiological and laboratory characteristics and outcomes of 21 patients living with HIV (PLHIV) who were diagnosed with concurrent histoplasmosis and TB between 2017 and 2021 in Guatemala City, Guatemala.

RESULTS

Most patients were male and were newly diagnosed with HIV. All patients had advanced HIV disease (AHD). They presented with a median CD4 count of 20 cells/µl. The most common symptoms reported by the patients were fever, weight loss, cough and diarrhoea. Twelve patients died within 6 months of baseline evaluation, for a mortality rate of 57.1%.

CONCLUSIONS

PLHIV with concurrent TB and histoplasmosis infections are characterised by AHD, predominantly presenting with disseminated forms of these infections and with unspecific symptoms and signs. This evidence calls for early HIV and opportunistic infection screening and insights into the challenges and opportunities for the efficient diagnostic and therapeutic management of patients with AHD with concurrent histoplasmosis and TB infections.

Histoplasma capsulatum as a cause for prolonged pulmonary illness in an immunocompetent returning traveller from Bangladesh

Fungal infections can be challenging to diagnose in returning travellers due to their non-specific clinical manifestations and changing epidemiology. We present a case of progressive disseminated histoplasmosis in a returning traveller from Bangladesh. The patient had a progressive and prolonged respiratory illness necessitating mechanical ventilatory support. The clue to potential fungal aetiology was provided by serum fungal markers - 1-3-β-D-glucan and Aspergillus galactomannan. Diagnosis was eventually made using panfungal PCR on bronchioalveolar lavage fluid.

Unveiling the menace: a thorough review of potential pandemic fungal disease

Fungal diseases have emerged as a significant global health threat, with the potential to cause widespread outbreaks and significant morbidity and mortality. Anticipating future pandemic fungal diseases is essential for effective preparedness and response strategies. This comprehensive literature review aims to provide a comprehensive analysis of the existing research on this topic. Through an extensive examination of scholarly articles, this review identifies potential fungal pathogens that have the potential to become pandemics in the future. It explores the factors contributing to the emergence and spread of these fungal diseases, including climate change, globalization, and antimicrobial resistance. The review also discusses the challenges in diagnosing and treating these diseases, including limited access to diagnostic tools and antifungal therapies. Furthermore, it examines the strategies and interventions that can be employed to mitigate the impact of future pandemic fungal diseases, such as improved surveillance systems, public health education, and research advancements. The findings of this literature review contribute to our understanding of the potential risks posed by fungal diseases and provide valuable insights for public health professionals and policymakers in effectively preparing for and responding to future pandemic outbreaks. Overall, this review emphasizes the importance of proactive measures and collaborative efforts to anticipate and mitigate the impact of future pandemic fungal diseases.

Disseminated Histoplasmosis Mimicking Macrophage Activation Syndrome in a Patient With Rheumatoid Arthritis

Infections caused by Histoplasma capsulatum typically do not produce symptoms. However, in individuals who are immunocompromised, progressive disseminated histoplasmosis may occur. A 67-year-old female, with lengthy history of immunosuppression due to management of rheumatoid arthritis, reported a two-month history of fatigue, headaches, and intermittent fevers following hip surgery. Due to the concern for macrophage activation syndrome and hemophagocytic lymphohistiocytosis, a bone marrow biopsy was performed. However, the results indicated the presence of Histoplasma, which was supported by the presence of Histoplasma antigens in the serum and urine, Histoplasma antibodies in the serum, positive (1,3)-beta-D-glucan results, and fungal blood cultures. The patient initially received amphotericin B, but it was switched to itraconazole due to adverse effects. The patient remains on itraconazole therapy and follows as an outpatient with an infectious diseases specialist.

Design of a Multi-Epitope Vaccine against Histoplasma capsulatum through Immunoinformatics Approaches

Histoplasmosis is a widespread systemic disease caused by Histoplasma capsulatum, prevalent in the Americas. Despite its significant morbidity and mortality rates, no vaccines are currently available. Previously, five vaccine targets and specific epitopes for H. capsulatum were identified. Immunoinformatics has emerged as a novel approach for determining the main immunogenic components of antigens through in silico methods. Therefore, we predicted the main helper and cytotoxic T lymphocytes and B-cell epitopes for these targets to create a potential multi-epitope vaccine known as HistoVAC-TSFM. A total of 38 epitopes were found: 23 common to CTL and B-cell responses, 11 linked to HTL and B cells, and 4 previously validated epitopes associated with the B subunit of cholera toxin, a potent adjuvant. In silico evaluations confirmed the stability, non-toxicity, non-allergenicity, and non-homology of these vaccines with the host. Notably, the vaccine exhibited the potential to trigger both innate and adaptive immune responses, likely involving the TLR4 pathway, as supported by 3D modeling and molecular docking. The designed HistoVAC-TSFM appears promising against Histoplasma, with the ability to induce important cytokines, such as IFN-γ, TNF-α, IL17, and IL6. Future studies could be carried out to test the vaccine's efficacy in in vivo models.

Emerging trends in fungal endocarditis: clinical complexity, diagnostic challenges, and therapeutic implications - a case series and literature review

Background

Fungal infective endocarditis (IE) is a rare, yet increasingly recognised condition associated with substantial mortality rates. Candida and Histoplasma are among the notable causative agents, presenting diverse clinical manifestations and complexities in diagnosis and management.

Objectives

This study was undertaken to examine the clinical profiles, diagnostic challenges, treatment modalities, and outcomes of four compelling cases involving Candida and Histoplasma endocarditis.

Methods & Design

This was a descriptive case series study conducted from July 2021 to July 2023. All patients with definite/possible endocarditis diagnosed based on modified Duke's criteria were reviewed in this study. Data on demographics, risk factors, clinical signs and symptoms, echocardiography findings, microbiological aetiology, complications, treatment, and outcomes were collected.

Results

Among 212 suspected IE cases reviewed, 54 met the modified Duke's criteria for possible or definite IE, with four instances identified as fungal endocarditis. Candida species accounted for three cases, while an uncommon instance of Histoplasma Endocarditis (HE) was also observed. Clinical presentations varied, with fever and dyspnoea being prominent symptoms. Risk factors included chronic kidney disease, prior surgeries, prosthetic valves, and immunocompromised states. Diagnosis posed challenges due to the resemblance to bacterial IE, low blood culture yields, and delayed suspicion. Various diagnostic approaches, including blood cultures, serological markers, and imaging, were employed. Therapeutic strategies involved antifungal agents and surgical intervention, where feasible. However, despite prompt treatment initiation, many patients faced rapid clinical deterioration, emphasising the severity and aggressive nature of fungal endocarditis. Mortality rates remained notably high across the cohort.

Conclusion

This study highlights the criticality of early suspicion, prompt diagnosis, and a multidisciplinary approach to managing fungal endocarditis. While recognising the limitations in current diagnostic tools and therapeutic options, the study underscores the urgent need for enhanced diagnostic modalities and novel treatment strategies to improve outcomes in these challenging cases.

Histoplasmosis mimicking a tumor of the thumb in a patient with neurofibromatosis type I: A case report and review of the literature

We describe an immunocompromised 73-year-old male with a history of neurofibromatosis type 1 (NF1) who presented with a lesion on the thumb concerning for malignancy that was found to be histoplasmosis. This unique case highlights the importance of a thorough history and a broad differential diagnosis in the management of new osteoarticular lesions.

A Case of Disseminated Histoplasmosis Presenting As Adrenal Insufficiency With Granulomatous Hepatitis

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. In the United States, histoplasmosis is endemic in the Mississippi River Valley and Ohio. Histoplasmosis is often asymptomatic in immunocompetent individuals, and severe disseminated cases are more often seen in immunosuppressed patients. Disseminated histoplasmosis often affects the reticuloendothelial system, invading specific visceral organs such as the liver, spleen, and pancreas. The current study presents a unique case of disseminated histoplasmosis in a 64-year-old immunocompetent male. The patient's presentation included a 40-lb weight loss over a year, bilateral adrenal nodules, abnormal liver enzymes, and granulomatous hepatitis, which initially raised suspicion of a malignant etiology. An adrenal mass biopsy showed fungal morphology that confirmed an H. capsulatum infection. Further history showed that the patient recently traveled to Bangladesh, which is thought to be a region endemic to histoplasmosis. This case is noteworthy because disseminated histoplasmosis rarely affects immunocompetent individuals, and an infectious etiology for adrenal insufficiency is exceedingly rare, especially in the United States. The treatment regimen included a 14-day induction therapy of IV amphotericin B followed by outpatient itraconazole, leading to symptom resolution. This case highlights the need to consider an infectious etiology for adrenal insufficiency, especially among immunocompetent individuals who may be at risk after traveling to endemic areas.

Prevalence of Histoplasma Antigenuria among Outpatient Cohort with Advanced HIV in Kampala, Uganda

In sub-Saharan Africa, an estimated 25% of people with HIV present with advanced HIV and are at high risk of opportunistic infections. Whereas histoplasmosis has occasionally been seen in Uganda, the understanding of the local risk of acute infection is limited. We sought to determine the prevalence of Histoplasma antigenuria using an enzyme immunoassay (EIA, clarus Histoplasma GM EIA, IMMY; Norman, OK, USA) in a cohort of outpatients with advanced HIV disease in Kampala, Uganda. Among the persons with positive urine Histoplasma antigen tests, we assessed their clinical presentation and outcomes. The EIA was run on stored urine samples as per the manufacturer's instructions. Specimens ≥1 EIA units were considered positive. Among the 388 tested urine samples, 4 (1.2%) were positive for Histoplasma antigen. The histoplasmosis prevalence among participants with a CD4 < 100 cells/mcL was 2.5% (4/158). Three of the four participants with a positive Histoplasma antigen test reported systemic symptoms consistent with histoplasmosis. All four participants had a positive urine lipoarabinomannan test and were treated for tuberculosis. By the four-week follow-up visit, all participants were clinically improved, alive, and in care without antifungal therapy. In advanced HIV, the clinical presentations of tuberculosis and histoplasmosis overlap. The value of histoplasmosis screening and pre-emptive treatment is an area of future research.

Emergomycosis in Africa: Time to Pay Attention to This Emerging Deadly Fungal Infection

Emergomycosis is an emerging deadly infectious disease caused primarily by a little-known airborne pathogen Emergomyces africanus, which can cause clinical management challenge especially in patients with advanced HIV disease. This minireview describes Es. africanus as the main cause of emergomycosis in Africa as well as considers contributing factors to the difficulties encountered in managing this infection. Emergomycosis is common in HIV-positive persons with low CD4 lymphocyte count and has an estimated fatality of 50%. The infection exhibits airborne transmission with pulmonary and extrapulmonary manifestations leading to skin lesions. However, the pathogenesis of Es. africanus is still poorly understood. The management of the infection is complicated due to lack of defined diagnostic and therapeutic guidelines. Limited expertise, poor research funding, and lack of awareness and national surveillance are thought to impact the recognition and prioritisation of the infection. These factors may ultimately assign emergomycosis a 'neglected infection status' even as it is suspected to be prevalent in more African countries than previously recognised. Increased awareness and integrated and targeted strategies such as mobilising manpower in clinical mycology are of paramount importance in managing emergomycosis in Africa and beyond.

Histoplasma capsulatum prosthetic joint infection

Immunocompromised patients are at risk of opportunistic infections. This is a 67-year-old woman with systemic sclerosis and knee osteoarthritis who underwent left total knee arthroplasty in 2009. In 2018 she underwent surgery for presumed aseptic loosening. Inflammation and purulent fluid were found; implant was removed and replaced with a static spacer. Three weeks later, H. capsulatum was isolated. She was successfully treated with itraconazole for 18 months; cultures on revision spacer replacement surgery were negative.

A 54-Year-Old Woman With Rheumatoid Arthritis, Low-Grade Fever, and Cough

CASE PRESENTATION

A 54-year-old Indian woman presented with low-grade fever and cough with expectoration for 1 month. Fever was not associated with any chills or night sweats. Expectoration was minimal in amount and mucoid in nature. Her appetite was decreased, without any significant weight loss. She denied any history of dyspnea or hemoptysis. The patient was diagnosed with rheumatoid arthritis 1 year previously and was initially started on methotrexate and short-term glucocorticoids. At the time of presentation, she was taking methotrexate 15 mg weekly and hydroxychloroquine 200 mg daily. Her joint disease was controlled on immunomodulators. She had no other comorbid condition, and she was a never smoker. She neither traveled within or outside India in the past nor came in contact with patients with pulmonary TB. A chest radiograph was done because a prior workup showed an ill-defined solitary nodular lesion in the right lower zone. She took a course of amoxicillin-clavulanate, but that was of no benefit.

In silico-chemogenomic repurposing of new chemical scaffolds for histoplasmosis treatment

BACKGROUND

Histoplasmosis is a systemic form of endemic mycosis to the American continent and may be lethal to people living with HIV/AIDS. The drugs available for treating histoplasmosis are limited, costly, and highly toxic. New drug development is time-consuming and costly; hence, drug repositioning is an advantageous strategy for discovering new therapeutic options.

OBJECTIVE

This study was conducted to identify drugs that can be repositioned for treating histoplasmosis in immunocompromised patients.

METHODS

Homologous proteins among Histoplasma capsulatum strains were selected and used to search for homologous targets in the DrugBank and Therapeutic Target Database. Essential genes were selected using Saccharomyces cerevisiae as a model, and functional regions of the therapeutic targets were analyzed. The antifungal activity of the selected drugs was verified, and homology modeling and molecular docking were performed to verify the interactions between the drugs with low inhibitory concentration values and their corresponding targets.

RESULTS

We selected 149 approved drugs with potential activity against histoplasmosis, among which eight were selected for evaluating their in vitro activity. For drugs with low minimum inhibitory concentration values, such as mebendazole, everolimus, butenafine, and bifonazole, molecular docking studies were performed. A chemogenomic framework revealed lanosterol 14-α-demethylase, squalene monooxygenase, serine/threonine-protein kinase mTOR, and the β-4B tubulin chain of H. capsulatum, respectively, as the protein targets of the drugs.

CONCLUSIONS

Our strategy can be used to identify promising antifungal targets, and drugs with repositioning potential for treating H. capsulatum.

Addressing Microbial Resistance Worldwide: Challenges over Controlling Life-Threatening Fungal Infections

Fungal infections are a serious global concern because of their ability to spread and colonize host tissues in immunocompromised individuals. Such infections have been frequently reported worldwide and are currently gaining clinical research relevance owing to their resistant character, representing a bottleneck in treating affected people. Resistant fungi are an emergent public health threat. The upsurge of such pathogens has led to new research toward unraveling the destructive potential evoked by these species. Some fungi-grouped into Candida, Aspergillus, and Cryptococcus-are causative agents of severe and systemic infections. They are associated with high mortality rates and have recently been described as sources of coinfection in COVID-hospitalized patients. Despite the efforts to elucidate the challenges of colonization, dissemination, and infection severity, the immunopathogenesis of fungal diseases remains a pivotal characteristic in fungal burden elimination. The struggle between the host immune system and the physiological strategies of the fungi to maintain cellular viability is complex. In this brief review, we highlight the relevance of drug resistance phenotypes in fungi of clinical significance, taking into consideration their physiopathology and how the scientific community could orchestrate their efforts to avoid fungal infection dissemination and deaths.

Isolated Colonic Histoplasmosis in Patients Undergoing Immunomodulator Therapy: A Systematic Review

Gastrointestinal histoplasmosis remains an inconspicuous clinicopathologic entity. It is predominantly considered a protean manifestation of disseminated disease. We hereby delineate a unique case of biopsy-proven isolated colonic histoplasmosis in a patient undergoing methotrexate therapy. Furthermore, we present the first systematic review of the MEDLINE, Google Scholar, Embase, and Scopus databases regarding isolated colonic histoplasmosis in adult patients receiving immunomodulator therapy (IMT). A total of 13 case reports (level of clinical evidence: IV) were identified. The mean age was 55.6 ± 11.1 years, with 9 (69.2%) cases reported in women. Patients with subclinical disease (5, 38.5%) were often incidentally diagnosed by screening colonoscopy. Symptomatic individuals predominantly presented with diarrhea (4, 30.8%), weight loss (3, 23.1%), and/or abdominal pain (3, 23.1%). IMT was mainly administered for liver transplant (4, 30.8%), renal transplant (4, 30.8%), and ulcerative colitis (2, 15.4%). Common colonoscopy features included colonic ulcerations (7, 53.8%), polyps or pseudopolyps (3, 23.1%), and/or mass-like lesions (3, 23.1%). Diagnosis was made by histology of colonic biopsy in 11 (84.6%) and resected specimens in 2 (15.4%) patients. Treatment consisted of a combination of amphotericin B with oral itraconazole in 6 (46.2%), oral itraconazole alone in 5 (38.5%), and amphotericin B alone in 2 (15.4%) patients. Complete clinical recovery was achieved in all patients. This article illustrates that isolated colonic involvement can be the only clinical presentation of histoplasmosis. It may masquerade as other bowel disorders, presenting diagnostic and therapeutic conundrums. Gastroenterologists should rule out colonic histoplasmosis in IMT recipients who develop unexplained colitis symptoms.

Two Cases of Hemophagocytic Lymphohistiocytosis Associated with Disseminated Histoplasmosis Presented with Transient Pancytopenia

Transient pancytopenia due to reactive bone marrow suppression often occurs in hemophagocytic lymphohistiocytosis (HLH), a syndrome resulting from excessive immune activation following a severe infection. We reported two cases with pancytopenia and disseminated histoplasmosis accompanied by HLH, initially suspected to be blood malignancies. Our first case documented the relevance between the improvement of pancytopenia and the clearance of Histoplasma capsulatum in serial bone marrow aspirations. The second case showed immense Histoplasma engulfment by the macrophage in relation to a severe clinical condition, followed by improvement of clinical symptoms in accordance with the recovery of pancytopenia. These two cases highlighted the importance of comprehensive and critical analysis for cases with concurrent pancytopenia and severe infection, since it may be that the pancytopenia underlies the severe infection or vice versa.

Challenges in Serologic Diagnostics of Neglected Human Systemic Mycoses: An Overview on Characterization of New Targets

Systemic mycoses have been viewed as neglected diseases and they are responsible for deaths and disabilities around the world. Rapid, low-cost, simple, highly-specific and sensitive diagnostic tests are critical components of patient care, disease control and active surveillance. However, the diagnosis of fungal infections represents a great challenge because of the decline in the expertise needed for identifying fungi, and a reduced number of instruments and assays specific to fungal identification. Unfortunately, time of diagnosis is one of the most important risk factors for mortality rates from many of the systemic mycoses. In addition, phenotypic and biochemical identification methods are often time-consuming, which has created an increasing demand for new methods of fungal identification. In this review, we discuss the current context of the diagnosis of the main systemic mycoses and propose alternative approaches for the identification of new targets for fungal pathogens, which can help in the development of new diagnostic tests.

Disseminated histoplasmosis in a renal transplantation recipient: Peripheral blood smear was the key

Disseminated histoplasmosis is common in immunocompromised patients such as patients with AIDS, hematologic malignancies, transplant recipients, and those on prolonged corticosteroid use. We report the case of a 53-year-old man with a history of end-stage renal disease due to uncontrolled hypertension who underwent renal transplantation in 2013. He presented to the hospital with a 5-day history of dyspnea, and blood tests showed pancytopenia. The diagnosis of disseminated histoplasmosis was made rapidly by peripheral blood smear. We encourage clinicians to check peripheral blood smear if disseminated histoplasmosis is suspected.

Histoplasmosis in Children; HIV/AIDS Not a Major Driver

The classification of histoplasmosis as an AIDS-defining illness has largely attributed its occurrence in people to the presence of HIV/AIDS especially in Africa. Prior to the advent of the HIV/AIDS epidemic, several cases of histoplasmosis were documented both in the pediatric and adult populations. Our review revealed 1461 reported cases of pediatric histoplasmosis globally in the last eight decades (1939-2021). North America (n = 1231) had the highest number of cases, followed by South America (n = 135), Africa (n = 65), Asia (n = 26) and Europe (n = 4). Histoplasmosis was much more common in the non-HIV pediatric population (n = 1418, 97.1%) compared to the HIV population. The non-HIV factors implicated were, childhood malignancies (n = 207), such as leukemias and lymphomas as well as their treatment, lung diseases (n = 7), environmental exposures and toxins (n = 224), autoimmune diseases (n = 12), organ transplants (n = 12), long-term steroid therapy (n = 3), the use of immunosuppressive drugs such as TNF-alpha inhibitors (n = 7) malnutrition (n = 12), histiocytosis (n = 3), Hyper immunoglobulin M and E syndromes (n = 15, 1.2%), pancytopenia (n = 26), diabetes mellitus (n = 1) and T-cell deficiency (n = 21). Paediatricians should always consider or rule out a diagnosis of histoplasmosis in children presenting with symptoms suggestive of the above clinical conditions.

Current and New Perspectives in the Diagnosis of Blastomycosis and Histoplasmosis

The diagnosis of blastomycosis and histoplasmosis can be difficult for clinicians who rarely see infections caused by these environmentally restricted dimorphic fungi. Historically, the diagnosis of blastomycosis has been established by culture and sometimes by histopathologic identification. Currently, antigen detection in urine and serum has been shown to aid in the rapid diagnosis of blastomycosis, and newer antibody assays are likely to contribute to our diagnostic capability in the near future. The gold standard for the diagnosis of histoplasmosis has been culture of the organism from involved tissues, aided in some patients by histopathological verification of the typical yeast forms in tissues. Antigen detection has contributed greatly to the ability of clinicians to rapidly establish the diagnosis of histoplasmosis, especially in severely ill and immunocompromised patients, and antibody testing for Histoplasma capsulatum provides important adjunctive diagnostic capability for several forms of both acute and chronic histoplasmosis. For both of these endemic mycoses, novel molecular tests are under active investigation, but remain available in only a few reference laboratories. In this review, we provide a synopsis of diagnostic test options that aid in establishing whether a patient has blastomycosis or histoplasmosis.