Histoplasmosis

Acute Myelopathy as Initial Presentation of Disseminated Histoplasmosis: A Case Report

Histoplasmosis is a fungal infection caused by the fungus Histoplasma capsulatum that can rarely present with central nervous system (CNS) manifestations that include meningitis, encephalitis, focal brain or spinal cord lesions, and stroke syndromes. Because of this variation from patient to patient, CNS histoplasmosis is a difficult clinical diagnosis to make, which can be further hindered by no highly sensitive diagnostic testing available. Here, we present a unique case of a 46-year-old male immunocompromised due to type 1 diabetes mellitus with disseminated histoplasmosis as an acute presentation of myelopathy. Patient had left leg weakness for a few days prior to presentation and a neurological exam remarkable for signs of acute thoracic myelopathy, specifically concerning for Brown-Séquard syndrome. MRI imaging demonstrated an enhancing thoracic spinal cord lesion along with multiple cerebral enhancing lesions, bilateral adrenal masses, and innumerable pulmonary nodules. Biopsy results demonstrated yeast forms consistent with Histoplasma species.

Evolving Epidemiology, Improving Diagnostic Tests and Their Importance for the Correct Diagnosis of Histoplasmosis

Histoplasmosis has traditionally been described as having discrete geographic areas of endemicity. Over the last few decades, it has become more and more clear that these areas are not accurate depictions of where histoplasmosis can occur. Our understanding of where histoplasmosis occurs has improved in recent years due to improving access to diagnostic testing and increased reporting as well as larger at-risk populations (HIV and non-HIV immune suppression) resulting in more cases. Although areas of relatively higher risk and case numbers certainly still exist, histoplasmosis has been observed in much of the world at this point. Our knowledge of the geographic distribution of histoplasmosis, though improving, remains incomplete. While diagnostic testing has traditionally been confined to visualization and/or culture in much of the world, antigen testing has emerged as an excellent tool. Unfortunately access to antigen testing has been inadequate for much of the world, but this has started to change in recent years and will likely change more dramatically in the near future, assuming ongoing positive developments in the area of lateral flow tests for antigen testing. In this review, we describe the current understanding of the geographic distribution of histoplasmosis, the current landscape of diagnostic testing, and the evolution of both areas with an eye towards the future.

Histoplasmosis

This review provides an update of histoplasmosis, covering the changing epidemiology, pathogenesis, disease manifestations, diagnostic strategies, and management considerations for immunocompetent and immunocompromised populations.

Histoplasmosis - More common than we realize

Histoplasmosis is primarily associated with immunocompromised individuals; however, its presentation in immunocompetent patients is increasingly recognized. This series of 5 cases from eastern India, a potential Histoplasmosis hotspot, describes five immunocompetent individuals with the disease. It emphasizes the diverse clinical spectrum of Histoplasmosis, often mimicking other conditions, thereby complicating diagnosis. Four patients presented with adrenal masses, emphasizing the importance of considering histoplasmosis in the differential diagnosis of adrenal enlargement. One patient developed hemophagocytic lymphohistiocytosis (HLH), underscoring the severe complications associated with disseminated histoplasmosis. Additionally, one patient exhibited localized disease, demonstrating the variable clinical presentations of this infection. Our findings emphasize the need for heightened clinical suspicion of histoplasmosis in patients with adrenal masses or unexplained fever, even in immunocompetent individuals in a relevant epidemiological setting. Early diagnosis and appropriate antifungal therapy are crucial for optimal outcomes.

Disseminated Histoplasmosis Presenting with Panniculitis and Macrophage Activation Syndrome in a Patient Undergoing Immunosuppressive Therapy for Mixed Connective Tissue Disease (MCTD)

Histoplasmosis, a fungal infection caused by Histoplasma capsulatum, is endemic in many parts of the world. However, this is not common in Japan. We herein present a unique case of military histoplasmosis in a 45-year-old female with mixed connective tissue disease (MCTD) who was receiving immunosuppressive therapy. The histological findings coupled with molecular confirmation led to final a diagnosis. This case emphasizes the diagnostic challenges associated with histoplasmosis in immunocompromised patients and underscores the importance of considering it in the differential diagnosis of any atypical presentation in rheumatic patients.

Case report: Primary infection of conjunctival histoplasmosis mimicking a large conjunctival neoplasm in an immunosuppressed patient

We report a rare case of a rapidly growing and large conjunctival histoplasmosis lesion in an immunosuppressed West African woman in her 80s, affecting her only eye. The patient had undergone a renal transplant and was on immunosuppressive medications. Additionally, she had previously been treated for presumed systemic histoplasmosis with itraconazole more than 5 years ago. Despite receiving previous treatment, she presented with a large conjunctival lesion, which was confirmed to be histoplasmosis after an excisional biopsy. The lesion was observed to grow over a 2-week period, causing significant visual impairment. Following a comprehensive systems review and investigation, the conjunctiva was identified as the sole site of infection. This case underscores the rarity of sight-threatening Histoplasma infections in the conjunctiva of an immunosuppressed individual. Conjunctival histoplasmosis lesions are rarely reported, with even fewer cases documented as primarily originating from this location.

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.

Disseminated Histoplasmosis in an Immunocompetent Patient from Southern Arizona

In this review, we present a case report of an immunocompetent 58-year-old male who presented with disseminated histoplasmosis (DH) outside of the known endemic regions. Due to his atypical clinical presentation that did not fit the classical clinical picture of DH, the diagnosis was delayed. In addition, we researched DH in the immunocompetent hosts as these cases are not common and leave the patient population vulnerable to delayed diagnosis. The literature supports considering histoplasmosis in the differential diagnosis among patients who present with possible exposures outside of endemic regions and are immunocompetent.

Disseminated Histoplasmosis Diagnosed in an Immunocompetent Patient from a Non-Endemic Area: Neglected or Emerging Disease?

Histoplasma capsulatum (H. capsulatum) is considered to be one of the most extensively spread dysmorphic fungi worldwide. Histoplasmosis primarily impacts patients with weakened immune systems and can result in a diverse range of clinical manifestations. In immunocompetent patients, the disease may manifest as a self-limiting or asymptomatic infection; however, in immunocompromised individuals, it can occur as a debilitating, disseminated disease. Diagnosing histoplasmosis may be challenging. A medical professional that specializes in treating endemic fungal illnesses is better able to assist with an accurate and timely diagnosis since they have a deeper grasp of these illnesses. Consequently, the process of diagnosing histoplasmosis might be difficult for less experienced physicians. The case presented is an example of the myriad faces that histoplasmosis can take on, mimicking other common infectious or malignant conditions, leading to extensive work-up and invasive procedures in establishing the diagnosis of this otherwise benign condition. We hereby report the case of disseminated histoplasmosis in a young immunocompetent female patient.

Development of a TaqMan probe-based multiplex real-time PCR for the simultaneous detection of four clinically important filamentous fungi

Filamentous fungi present significant health hazards to immunocompromised individuals globally; however, the prompt and precise identification of them during infection remains challenging. In this study, a TaqMan probe-based multiplex real-time PCR (M-qPCR) assay was developed to detect simultaneously the target genes of four important pathogenic filamentous fungi: ANXC4 gene of Aspergillus fumigatus, EF1-α gene of Fusarium spp., mitochondrial rnl gene of Mucorales, and hcp100 gene of Histoplasma capsulatum. In this M-qPCR assay, the limit of detection (LoD) to all four kinds of fungi was 100 copies and the correlation coefficients (R2) were above 0.99. The specificity of this assay is 100%, and the minimum detection limit is 100 copies/reaction. In conclusion, an M-qPCR detection assay was well established with high specificity and sensitivity for rapid and simultaneous detection on four important filamentous fungi in the clinic.

IMPORTANCE

World Health Organization developed the first fungal priority pathogens list (WHO FPPL) in 2022. Aspergillus fumigatus, Mucorales, Fusarium spp., and Histoplasma spp. are the four types of pathogenic fungi with filamentous morphology in the critical priority group and high priority group of WHO FPPL. These four filamentous fungal infections have become more common and severe in immunocompromised patients with the increase in susceptible populations in recent decades, which resulted in a substantial burden on the public health system. However, prompt and precise identification of them during infection remains challenging. Our study established successfully a TaqMan probe-based multiplex real-time qPCR assay for four clinically important filamentous fungi, A. fumigatus, Fusarium spp., Mucorales, and Histoplasma capsulatum, with high sensitivity and specificity, which shows promising potential for prompt and precise diagnosis against fungal infection.

The impact of immune recovery and treatment duration on disseminated histoplasmosis consolidation therapy in AIDS patients

INTRODUCTION

The present study investigated the impact of immune recovery and the duration of antifungal adherence in the consolidation phase of disseminated histoplasmosis (DH) in acquired immune deficiency syndrome (AIDS) patients living in a hyperendemic area in northeastern Brazil.

MATERIAL AND METHODS

Sixty-nine patients with DH/AIDS, admitted to the São José Hospital between 2010 and 2015, who continued histoplasmosis consolidation therapy at the outpatient clinic were studied. The follow-up duration was at least 24 months.

RESULTS

Sixty-eight patients used itraconazole 200-400 mg/day or amphotericin B deoxycholate weekly during the consolidation phase, and six patients relapsed during follow-up. The overall median duration of consolidation antifungal use was 250 days [IQR 101 - 372]. Antifungal withdrawal by medical decision occurred in 41 patients (70.7 %) after a median of 293 days [IQR 128 - 372] of use; 16 patients discontinued by their own decision, with a median of 106 days [IQR 37 - 244] of therapy; three patients had no information available, and nine continued on AF therapy. The median CD4+ T-cell count in the group without relapse was 248 cells/µL [IQR 115-355] within 6 months after admission; conversely, in the relapse group, the median cell count remained below 100 cells/µL. Irregular adherence to highly active antiretroviral therapy (HAART) was the leading risk factor associated with relapse and death (p< 0.01).

DISCUSSION

The regular use of HAART, combined with immune recovery, proved to be highly effective in preventing relapses in DH/AIDS patients, suggesting that long-term antifungal therapy may not be necessary.

Respiratory Compromise Related to Primary Histoplasmosis Infection in Two Pediatric Patients

Primary infection related to the fungus, histoplasmosis, is generally asymptomatic in immunocompetent hosts. Calcified granulomas may be noted incidentally on radiologic imaging such as chest radiographs or computed tomography imaging. However, even in immunocompetent hosts, these primary infections occasionally result in end-organ involvement including respiratory compromise. Histoplasmosis should be included in the differential diagnosis of patients presenting with respiratory involvement and mediastinal adenopathy. We present two pediatric-aged patients who developed pulmonary involvement related to a primary histoplasmosis infection that resulted in mediastinal and tracheal lymphadenopathy. These led to respiratory compromise due to pleural effusion in the first patient and tracheal compression in the second. In this paper, the basic microbiology of Histoplasma capsulatum is presented, previous reports of primary respiratory involvement presented, and diagnostic and therapeutic options discussed.

Histoplasmosis in non-immunosuppressed patients from an endemic area in Northeastern Brazil

Differently from immunocompromised patients, very little information is available in the literature regarding the clinical presentation, epidemiology, and outcomes of histoplasmosis in non-immunosuppressed individuals living in endemic areas. This retrospective case series study was carried out by reviewing the medical records of non-immunocompromised patients with histoplasmosis, residents in a hyperendemic area in northeastern Brazil, between 2011 and 2022. Thirty HIV-negative patients were identified with histoplasmosis, and 19 cases met the inclusion criteria: three had acute, five subacute and one chronic pulmonary forms; two with mediastinal picture and eight had disseminated disease (two with severe symptoms). The median age of our sample was 32.7 years old [interquartile range: 24-45]. Most of the patients were male (male-to-female ratio = 15:4) and resided in the state capital (n = 9). The majority had a previous history of exposure to well-known risk factors for Histoplasma infection. Pulmonary nodules were observed in all subacute form, two patients (acute and subacute forms) were initially treated empirically for pulmonary tuberculosis; one death was registered in the subacute form. The chronic pulmonary form of histoplasmosis was diagnosed in one patient only after the symptoms persisted despite specific treatment. The primary clinical manifestations of the moderate form of DH were enlarged lymph nodes, with histopathology being the main diagnostic method. The cases were detected as isolated occurrences and not as an outbreak, suggesting that exposure to Histoplasma can be more widespread than presumed. Despite the self-limiting nature of the disease, death can occur even in previously heathy patients.

Mucocutaneous histoplasmosis as the first manifestation of AIDS

Immunosuppressed patients can present with opportunistic infections resulting from an intrinsic systemic disease, which easily evolves into more aggressive and less common conditions. This work reports a clinical case of a female patient with histoplasmosis lesions in the nasal and oral mucosa, including pulmonary, hematological, and hepatic impairment, which led to the diagnosis of HIV seropositivity. In the presence of severe immunosuppression, morbidity is increased due to deep fungal infections and their unusual clinical characteristics can make diagnosis difficult. Therefore, it can be very helpful to recognize these clinical characteristics in order to determine early diagnostic interventions. It is important to recognize mucocutaneous manifestations of histoplasmosis because the biopsy of these lesions, and subsequent histopathological analysis, is one of the quickest, safest, and cheapest methods of diagnosis.

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.

Common virulence factors between Histoplasma and Paracoccidioides: Recognition of Hsp60 and Enolase by CR3 and plasmin receptors in host cells

Over the last two decades, the incidence of Invasive Fungal Infections (IFIs) globally has risen, posing a considerable challenge despite available antifungal therapies. Addressing this, the World Health Organization (WHO) prioritized research on specific fungi, notably Histoplasma spp. and Paracoccidioides spp. These dimorphic fungi have a mycelial life cycle in soil and a yeast phase associated with tissues of mammalian hosts. Inhalation of conidia and mycelial fragments initiates the infection, crucially transforming into the yeast form within the host, influenced by factors like temperature, host immunity, and hormonal status. Survival and multiplication within alveolar macrophages are crucial for disease progression, where innate immune responses play a pivotal role in overcoming physical barriers. The transition to pathogenic yeast, triggered by increased temperature, involves yeast phase-specific gene expression, closely linked to infection establishment and pathogenicity. Cell adhesion mechanisms during host-pathogen interactions are intricately linked to fungal virulence, which is critical for tissue colonization and disease development. Yeast replication within macrophages leads to their rupture, aiding pathogen dissemination. Immune cells, especially macrophages, dendritic cells, and neutrophils, are key players during infection control, with macrophages crucial for defense, tissue integrity, and pathogen elimination. Recognition of common virulence molecules such as heat- shock protein-60 (Hsp60) and enolase by pattern recognition receptors (PRRs), mainly via the complement receptor 3 (CR3) and plasmin receptor pathways, respectively, could be pivotal in host-pathogen interactions for Histoplasma spp. and Paracoccidioides spp., influencing adhesion, phagocytosis, and inflammatory regulation. This review provides a comprehensive overview of the dynamic of these two IFIs between host and pathogen. Further research into these fungi's virulence factors promises insights into pathogenic mechanisms, potentially guiding the development of effective treatment strategies.

Disseminated Histoplasmosis Infection Diagnosed by Metagenomic Next-Generation Sequencing: A Case Report

Histoplasmosis is an endemic disease caused by Histoplasma capsulatum. This systemic disease can affect various organs beyond the lungs, such as the liver, spleen, adrenal gland, and lymph nodes. The clinical symptoms can range from asymptomatic to severe, life-threatening conditions, depending on the state of the patient's immune system. This report describes a 40-year-old male who presented with reports of weight loss, low back pain, and progressively worsening movement disorder of the bilateral lower extremities for months. Computed tomography (CT) examination showed multiple lytic lesions of vertebral bodies, bilateral ribs, and pelvic bone, histopathological examination and tumor-related serum markers exclude tumors. mNGS was employed to identify H. capsulatum var. capsulatum as the etiological agent of the lesions in the bone biopsy. Through phylogenetic tree analysis, Histoplasma capsulatum var. Capsulatum (Hcc) was the main responsible pathogen, rarely reported in bone lesions. The patient underwent spinal surgery and was successfully treated with liposomal amphotericin B and itraconazole. Based on the diagnosis and treatment of this case, we discuss the epidemiologic status, clinical presentations, diagnostic criteria, and treatment guidelines of histoplasmosis to provide additional information about this disease. mNGS is utilized in this case, and it appears to be a reliable method for early and accurate diagnosis of this disease.

MSG-15: Super-Bioavailability Itraconazole Versus Conventional Itraconazole in the Treatment of Endemic Mycoses-A Multicenter, Open-Label, Randomized Comparative Trial

Background

Invasive fungal disease caused by dimorphic fungi is associated with significant morbidity and mortality. Super-bioavailability itraconazole (SUBA-itra) is a novel antifungal agent with pharmacokinetic advantages over currently available formulations. In this prospective comparative study, we report the outcomes of patients with endemic fungal infections (histoplasmosis, blastomycosis, coccidioidomycosis, and sporotrichosis).

Methods

This open-label randomized trial evaluated the efficacy, safety, and pharmacokinetics SUBA-itra compared with conventional itraconazole (c-itra) treatment for endemic fungal infections. An independent data review committee determined responses on treatment days 42 and 180.

Results

Eighty-eight patients were enrolled for IFD (SUBA-itra, n = 42; c-itra, n = 46) caused by Histoplasma (n = 51), Blastomyces (n = 18), Coccidioides (n = 13), or Sporothrix (n = 6). On day 42, clinical success was observed with SUBA-itra and c-itra on day 42 (in 69% and 67%, respectively, and on day 180 (in 60% and 65%). Patients treated with SUBA-itra exhibited less drug-level variability at days 7 (P = .03) and 14 (P = .06) of randomized treatment. The concentrations of itraconazole and hydroxyitraconazole were comparable between the 2 medications (P = .77 and P = .80, respectively). There was a trend for fewer adverse events (AEs; 74% vs 87%, respectively; P = .18) and serious AEs (10% vs 26%; P = .06) in the SUBA-itra-treated patients than in those receiving c-itra. Serious treatment-emergent AEs were less common in SUBA-itra-treated patients (12% vs 50%, respectively; P < .001).

Conclusions

SUBA-itra was bioequivalent, well tolerated, and efficacious in treating endemic fungi, with a more favorable safety profile than c-itra.

Clinical Trials Registration

NCT03572049.

Haemophagocytic lymphohistiocytosis secondary to disseminated histoplasmosis in an immunocompetent patient

Haemophagocytic lymphohistiocytosis secondary to Histoplasma infection is rare and almost always occurs in immunocompromised hosts. We report a 32-year-old immunocompetent man presenting with a nonspecific febrile illness found to have disseminated histoplasmosis and associated haemophagocytic lymphohistiocytosis. The diagnosis was confirmed on histopathological examination and PCR of liver and bone marrow biopsies. He was successfully treated with steroids, intravenous immunoglobulin and itraconazole.

Histoplasmosis in Solid Organ Transplantation

Histoplasma capsulatum, the etiological agent for histoplasmosis, is a dimorphic fungus that grows as a mold in the environment and as a yeast in human tissues. It has a broad global distribution with shifting epidemiology during recent decades. While in immunocompetent individuals infection is usually self-resolving, solid organ transplant recipients are at increased risk of symptomatic disease with dissemination to extrapulmonary tissue. Diagnosis of histoplasmosis relies on direct observation of the pathogen (histopathology, cytopathology, and culture) or detection of antigens, antibodies, or nucleic acids. All transplant recipients with histoplasmosis warrant therapy, though the agent of choice and duration of therapy depends on the severity of disease. In the present article, we describe the pathogenesis, epidemiology, clinical manifestations and management of histoplasmosis in solid organ transplant recipients.

Re-estimation of the burden of serious fungal diseases in Uganda

Background

It is of utmost importance to monitor any change in the epidemiology of fungal diseases that may arise from a change in the number of the at-risk population or the availability of local data.

Objective

We sought to update the 2015 publication on the incidence and prevalence of serious fungal diseases in Uganda.

Methods

Using the Leading International Fungal Education methodology, we reviewed published data on fungal diseases and drivers of fungal diseases in Uganda. Regional or global data were used where there were no Ugandan data.

Results

With a population of ~45 million, we estimate the annual burden of serious fungal diseases at 4,099,357 cases (about 9%). We estimated the burden of candidiasis as follows: recurrent Candida vaginitis (656,340 cases), oral candidiasis (29,057 cases), and esophageal candidiasis (74,686 cases) in HIV-infected people. Cryptococcal meningitis annual incidence is estimated at 5553 cases, Pneumocystis pneumonia at 4604 cases in adults and 2100 cases in children. For aspergillosis syndromes, invasive aspergillosis annual incidence (3607 cases), chronic pulmonary aspergillosis (26,765 annual cases and 63,574 5-year-period prevalent cases), and prevalence of allergic bronchopulmonary aspergillosis at 75,931 cases, and severe asthma with fungal sensitization at 100,228 cases. Tinea capitis is common with 3,047,989 prevalent cases. For other mycoses, we estimate the annual incidence of histoplasmosis to be 646 cases and mucormycosis at 9 cases.

Conclusion

Serious fungal diseases affect nearly 9% of Ugandans every year. Tuberculosis and HIV remain the most important predisposition to acute fungal infection necessitating accelerated preventive, diagnostic, and therapeutic interventions for the management of these diseases.

Endemic mycoses - are we making progress in management?

PURPOSE OF REVIEW

The endemic fungi are a significant cause of morbidity and mortality in effected patients. The range of endemicity for these are expanding with infections observed outside of traditional locations. Enhanced diagnostic and treatment practices may significantly alter patient outcomes.

RECENT FINDINGS

Recently completed clinical trials have focused on an assessment of improving efficacy while minimizing patient toxicity. Practice changing trials have been completed in histoplasmosis showing the utility of a single up-front liposomal amphotericin B dose followed by standard itraconazole dosing. The recent evaluation of several antifungal options including isauvconazole in the treatment of coccidioidomycosis also show promise for additional therapeutic agents. A recently conducted trial has also shown the superiority of amphotericin B therapy over itraconazole in the treatment of talaromycosis.

SUMMARY

The increased range of endemic mycoses coupled with the growing immunocompromised patient population mandates continued investigation of improved diagnostic and therapeutic options. Advances in these areas have led to more rapid diagnosis and more efficacious antifungal therapy.

Traversing the Cell Wall: The Chitinolytic Activity of Histoplasma capsulatum Extracellular Vesicles Facilitates Their Release

Histoplasma capsulatum is the causative agent of histoplasmosis. Treating this fungal infection conventionally has significant limitations, prompting the search for alternative therapies. In this context, fungal extracellular vesicles (EVs) hold relevant potential as both therapeutic agents and targets for the treatment of fungal infections. To explore this further, we conducted a study using pharmacological inhibitors of chitinase (methylxanthines) to investigate their potential to reduce EV release and its subsequent impact on fungal virulence in an in vivo invertebrate model. Our findings revealed that a subinhibitory concentration of the methylxanthine, caffeine, effectively reduces EV release, leading to a modulation of H. capsulatum virulence. To the best of our knowledge, this is the first reported instance of a pharmacological inhibitor that reduces fungal EV release without any observed fungicidal effects.

Closing the Gap in Proteomic Identification of Histoplasma capsulatum: A Case Report and Review of Literature

Histoplasmosis is a globally distributed systemic infection caused by the dimorphic fungus Histoplasma capsulatum (H. capsulatum). This fungus can cause a wide spectrum of clinical manifestations, and the diagnosis of progressive disseminated histoplasmosis is often a challenge for clinicians. Although microscopy and culture remain the gold standard diagnostic tests for Histoplasma identification, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) has emerged as a method of microbial identification suitable for the confirmation of dimorphic fungi. However, to our knowledge, there are no entries for H. capsulatum spectra in most commercial databases. In this review, we describe the case of disseminated histoplasmosis in a patient living with HIV admitted to our university hospital that we failed to identify by the MALDI-TOF method due to the limited reference spectrum of the instrument database. Furthermore, we highlight the utility of molecular approaches, such as conventional polymerase chain reaction (PCR) and DNA sequencing, as alternative confirmatory tests to MALDI-TOF technology for identifying H. capsulatum from positive cultures. An overview of current evidence and limitations of MALDI-TOF-based characterization of H. capsulatum is also presented.

Disseminated Histoplasmosis Presenting as Obstructive Jaundice

Gastrointestinal manifestations in systemic fungal infection are not uncommon; however, obstructive jaundice due to lymphadenopathy is considered rare. We present a case of a 16-year-old male patient who presented with painless jaundice. Laboratory tests revealed direct hyperbilirubinemia with cholestatic liver injury. Chest and abdominal computed tomography showed mediastinal and porta hepatis lymphadenopathy, with severe biliary ductal dilatation proximal to an obstructing lymph node near the head of the pancreas. Endoscopic ultrasound showed a 22 × 35-mm lymph node with a mass effect on the common bile duct leading to obstructive jaundice. Infectious workup confirmed the diagnosis of disseminated histoplasmosis.

Invasive fungal infections in liver diseases

Patients with liver diseases, including decompensated cirrhosis, alcohol-associated hepatitis, and liver transplant recipients are at increased risk of acquiring invasive fungal infections (IFIs). These infections carry high morbidity and mortality. Multiple factors, including host immune dysfunction, barrier failures, malnutrition, and microbiome alterations, increase the risk of developing IFI. Candida remains the most common fungal pathogen causing IFI. However, other pathogens, including Aspergillus, Cryptococcus, Pneumocystis, and endemic mycoses, are being increasingly recognized. The diagnosis of IFIs can be ascertained by the direct observation or isolation of the pathogen (culture, histopathology, and cytopathology) or by detecting antigens, antibodies, or nucleic acid. Here, we provide an update on the epidemiology, pathogenesis, diagnosis, and management of IFI in patients with liver disease and liver transplantation.

The relevance of clinical and epidemiological correlation in the early diagnosis of histoplasmosis: report of two clinical cases in Popayán, Colombia

Histoplasmosis is an endemic mycosis in Colombia. Here we present two cases in the Cauca department, to indicate the clinical impact of histoplasmosis delayed diagnosis and treatment when its epidemiology is unknown. Informed consent was requested to review patients’ medical records and case report publication. The first case was a patient diagnosed with human immunodeficiency virus and generalized presence of skin lesions. Initially, these lesions were diagnosed as herpes, but a postmortem diagnosis confirmed histoplasmosis through fungal cultures of tissues from the skin lesions. The second case is an immunocompetent patient with pulmonary symptoms diagnosed and treated for tuberculosis. However, given the lack of improvement and considering the bat cave entrance history, the patient was treated for possible pulmonary histoplasmosis with an adequate response. We made a review of laboratory tests and histoplasmosis epidemiological data relevant to health professionals. We concluded that health institutions must provide rapid tests, such as antigen ones, to adequately diagnose and treat this mycosis; and also take corrective measures to minimize exposure to Histoplasma.

Infection of bats with Histoplasma species

Histoplasma species infect humans and animals, notably bats. Histoplasma species are thermally dimorphic fungi existing in mycelial form in the natural environment and in yeast form in infected tissues. In this narrative literature review, we summarize the occurrence of Histoplasma spp. in different species of bat tissues (n = 49) and in soil admixed with bat guano where the species of bat dwelling nearby has been identified (an additional 18 species likely infected) to provide an up-to-date summary of data. Most positive isolations are from the Americas and Caribbean, with some studies from Thailand, Malaysia, Nigeria, Slovenia, France, and Australia. We also summarize some of the early experimental work to elucidate pathogenicity, latency, immune response, and faecal excretion in bats. Given the recent recognition of the global extent of histoplasmosis, thermal dimorphism in Histoplasma spp., and global heating, additional work on understanding the complex relationship between Histoplasma and bats is desirable.

Sepsis in Immunocompromised Host and a Hematologic Complication

CASE PRESENTATION

A 43-year-old Puerto Rican man with a kidney transplant presented to the ED with 2 weeks of flu-like symptoms, nausea, and vomiting. He had plasma exchange therapy 2 months before for acute transplant rejection and has been tolerating a heightened immunosuppressive regimen. CT scans characterized opacities as possibly early tree-in-bud opacities (Fig 1A). Patient remained stable throughout hospital stay with an unremarkable workup and was discharged with doxycycline for nonspecific pneumonia.

The Current and Future States of Diagnostic Tests for Histoplasmosis with a Focus on People with HIV and Disseminated Histoplasmosis

Histoplasmosis is caused by Histoplasma capsulatum and, although endemic in large parts of the world, is often underrecognized in many locations. In addition to underrecognition, inadequate availability of diagnostic tests is a major contributor to poor outcomes in disseminated disease in people with HIV. For those with advanced HIV and disseminated disease, antibody testing is less useful. Culture and histopathology can be useful in this situation, but each has limitations, including variable sensitivity by site and, in the case of culture, the need for a biosafety level three laboratory and a long period of growth. Antigen testing has proven useful for disseminated histoplasmosis due to the excellent sensitivity of urine. Yet, turnaround is slower than ideal due to use in a limited number of centers. The development of lateral flow assays has the potential to make for true rapid point-of-care assays for histoplasmosis, but in order to meet that promise, the tests must be widely available and affordable.

Disseminated Histoplasmosis in a Patient With Acquired Immunodeficiency Syndrome in a Non-Endemic Region (California)

Histoplasmosis is caused by infection with Histoplasma capsulatum (H. capsulatum). Progressive disseminated histoplasmosis is a more severe form of histoplasmosis and is seldom diagnosed in non-endemic regions of the world owing to the fungus's geographical distribution. In the United States (USA), Histoplasma capsulatum is classically known to be endemic to the Mississippi and Ohio River valleys, and cases in non-endemic areas, such as the southwest USA, are exceedingly rare. Patients with acquired immunodeficiency syndrome (AIDS) are at risk for infection with H. capsulatum, and failure to recognize and treat histoplasmosis may be devastating to patients. In non-endemic regions, the proposed mechanism for disseminated histoplasmosis in AIDS patients is reactivation of a previous infection. Here, we present the case of a young male patient who presented to a southern California hospital with diarrhea, was diagnosed with AIDS, and developed acute hypoxic respiratory failure. Chest imaging revealed diffuse reticulonodular opacities, and histoplasmosis was confirmed by urine and serologic examination. He was subsequently treated with liposomal amphotericin B and safely discharged from the hospital with oral itraconazole therapy. This case contributes to the current limited body of literature citing histoplasmosis infections in California, and clinicians should consider histoplasmosis as a differential diagnosis in non-endemic regions.

A 40-Year-Old Man With Multiple Pulmonary Nodules and Mediastinal Lymphadenopathy With Positive Anti-Neutrophil Cytoplasmic Antibody Reveals an Unexpected Diagnosis

CASE PRESENTATION

A 40-year-old man with no significant medical history presented to the ED with a 2-day history of right-sided chest pain accompanied by night sweats and chills. These symptoms were accompanied by a dry, nonproductive cough without hemoptysis. The patient worked as an air traffic controller, with a side business of buying, renovating, and selling houses. He takes part in the remodeling work himself but denies any exposure to animal droppings, bird droppings, or mold. He denied chronic sinus disease, rash, or arthralgias. A resident of Platte City, Missouri, he had recently traveled to Salt Lake City, Utah. At the time of presentation, the patient denied any fever or shortness of breath. He had no history of nicotine, alcohol, or illicit substance use and denied any recent weight loss.

Bilateral adrenal histoplasmosis presenting as adrenal mass mimicking malignancy in an immunocompetent patient

We report a case of a 78-year-old immunocompetent man who presented with worsening fatigue and lethargy for one month. He had also been complaining of cough and SOB for two months which had been attributed to his underlying COPD and possible pneumonia. CT showed bilateral pleural effusions, ground-glass opacities, cirrhosis, splenomegaly and bilateral adrenal masses which was highly suspicious for malignancy. After pheochromocytoma was ruled out, EUS-FNA guided biopsy was performed on the left adrenal gland. Histology was positive for yeast cells, with fungal staining (PAS) revealing narrow-based budding compatible with Histoplasma. The patient was treated with amphotericin and itraconazole. Our case is unique as he presented with hepatosplenomegaly, which is reported in less than a quarter of cases. Although typically a diagnosis in immunocompromised patients, a high index of clinical suspicion is required to diagnose disseminated histoplasmosis in an immunocompetent patient. The gold standard for diagnosis is fungal tissue culture. However results may take up to weeks. EUS-FNA guided biopsy of adrenal glands can aid in early definitive diagnosis and management.

Histoplasmosis at a Reference Center for Infectious Diseases in Southeast Brazil: Comparison between HIV-Positive and HIV-Negative Individuals

Objectives: Histoplasmosis is a systemic mycosis, present globally. We aimed to describe cases of histoplasmosis (Hc) and to establish a risk profile associated with Hc in HIV-infected patients (HIV+). Methods: This was a retrospective study of patients with a clinical laboratory diagnosis of Hc. Data were fed into REDCap, and statistical analysis was performed with R. Results: We included 99 records, 65 HIV+ and 34 HIV-. Average age was 39 years. Median time from onset to diagnosis was 8 weeks in HIV- and 22 weeks in HIV+. Disseminated histoplasmosis occurred in 79.4% of HIV+, vs. 36.4% of HIV- patients. Median CD4 count was 70. Co-infection with tuberculosis was present in 20% of HIV+ patients. Blood cultures were positive in 32.3% of HIV+ vs. 11.8% of HIV- (p = 0.025) patients; bone marrow culture was positive in 36.9% vs. 8.8% (p = 0.003). Most HIV+ patients (71.4%) were hospitalized. On univariate analysis, anemia, leukopenia, intensive care, use of vasopressors and mechanical ventilation were associated with death in HIV+ patients. Conclusions: Most of our patients with histoplasmosis were HIV+, presenting advanced AIDS. Diagnosis was late in HIV+ patients, and they frequently presented disseminated Hc, required hospitalization, and died. Early screening for Hc in HIV+ and drug-induced immunosuppressed patients is crucial.

Acute pulmonary histoplasmosis of immunocompetent subjects from Martinique, Guadeloupe and French Guiana: a case series

INTRODUCTION

Histoplasmosis is a fungal disease caused by Histoplasma capsulatum. Histoplasma capsulatum var capsulatum is found in Martinique. Cluster cases following working in deserted house, have been described in Martinique. Cases of acute pulmonary histoplasmosis have been described in immunosuppressed individuals, or in case of substantial exposure to reservoirs of Histoplasma capsulatum; however, cases of acute histoplasmosis are rare in immunocompetent individuals.

CASES SERIES

We report a series of 4 cases of sporadic acute pulmonary histoplasmosis in immunocompetent subjects. Investigation revealed definite exposure in one patient and 3 cases with potential exposure. The diagnosis was microbiological and histological in 3 patients and histological in one patient. All subjects had positive serology to histoplasmosis. Pulmonary involvement was in the form of nodules and micronodules in 3 cases and ground glass lesions in one case. Patients were treated with itraconazole for 3 months and all had a favourable outcome.

CONCLUSION

We report a series of 4 cases of acute pulmonary histoplasmosis in immunocompetent individuals, occurring in a context where exposure was uncertain. This raises the problem of occult exposure in the Caribbean. Interventions to raise awareness and encourage caution are warranted targeting the population of the French West Indies and French Guiana.

Pulmonary Histoplasmosis: A Clinical Update

Histoplasma capsulatum, the etiological agent for histoplasmosis, is a dimorphic fungus that grows as a mold in the environment and as a yeast in human tissues. The areas of highest endemicity lie within the Mississippi and Ohio River Valleys of North America and parts of Central and South America. The most common clinical presentations include pulmonary histoplasmosis, which can resemble community-acquired pneumonia, tuberculosis, sarcoidosis, or malignancy; however, certain patients can develop mediastinal involvement or progression to disseminated disease. Understanding the epidemiology, pathology, clinical presentation, and diagnostic testing performance is pivotal for a successful diagnosis. While most immunocompetent patients with mild acute or subacute pulmonary histoplasmosis should receive therapy, all immunocompromised patients and those with chronic pulmonary disease or progressive disseminated disease should also receive therapy. Liposomal amphotericin B is the agent of choice for severe or disseminated disease, and itraconazole is recommended in milder cases or as "step-down" therapy after initial improvement with amphotericin B. In this review, we discuss the current epidemiology, pathology, diagnosis, clinical presentations, and management of pulmonary histoplasmosis.

Comparative Genomics of Histoplasma capsulatum and Prediction of New Vaccines and Drug Targets

Histoplasma capsulatum is a thermodymorphic fungus that causes histoplasmosis, a systemic mycosis that presents different clinical manifestations, ranging from self-limiting to acute lung infection, chronic lung infection and disseminated infection. Usually, it affects severely immunocompromised patients although immunocompetent patients can also be infected. Currently, there are no vaccines to prevent histoplasmosis and the available antifungal treatment presents moderate to high toxicity. Additionally, there are few options of antifungal drugs. Thus, the aim of this study was to predict possible protein targets for the construction of potential vaccine candidates and predict potential drug targets against H. capsulatum. Whole genome sequences from four previously published H. capsulatum strains were analyzed and submitted to different bioinformatic approaches such as reverse vaccinology and subtractive genomics. A total of four proteins were characterized as good protein candidates (vaccine antigens) for vaccine development, three of which are membrane-bound and one is secreted. In addition, it was possible to predict four cytoplasmic proteins which were classified as good protein candidates and, through molecular docking performed for each identified target, we found four natural compounds that showed favorable interactions with our target proteins. Our study can help in the development of potential vaccines and new drugs that can change the current scenario of the treatment and prevention of histoplasmosis.

Histoplasma capsulatum modulates the immune response, affects proliferation and differentiation, and induces apoptosis of mesenchymal stromal cells

Mesenchymal stromal cells (MSC) have been widely used not only for tissue regeneration but also for the treatment of various diseases; however, it has been shown that infection of MSCs by different pathogens can attenuate their intrinsic immunomodulatory properties, affecting the proliferation and differentiation of these cells. Currently, the mechanisms by which MSCs respond to pathogen invasion are poorly understood. Therefore, the objective of the present study was to determine if the infection of bone marrow-derived MSCs, with yeasts of the pathogenic fungus Histoplasma capsulatum affects the activation, differentiation and/or proliferation of the MSCs. The results indicate that MSCs have the ability to phagocytose H. capsulatum yeasts but do not exert a notable antifungal effect. On the contrary, the infection of the MSCs with this fungal pathogen not only modulates the expression of inflammatory mediators by a mechanism dependent on TLR2, TLR4 and Dectin-1 but also affects the viability and differentiation capacity of the MSCs. These findings suggest that infection of MSCs by H. capsulatum could not only affect haematopoiesis but also modulate the immune response in the infected host and, furthermore, these MSCs could provide a niche for the fungus, allowing it to persist and evade the immune response of the host.

Identifying Potential Molecular Targets in Fungi Based on (Dis)Similarities in Binding Site Architecture with Proteins of the Human Pharmacolome

Invasive fungal infections represent a public health problem that worsens over the years with the increasing resistance to current antimycotic agents. Therefore, there is a compelling medical need of widening the antifungal drug repertoire, following different methods such as drug repositioning, identification and validation of new molecular targets and developing new inhibitors against these targets. In this work we developed a structure-based strategy for drug repositioning and new drug design, which can be applied to infectious fungi and other pathogens. Instead of applying the commonly accepted off-target criterion to discard fungal proteins with close homologues in humans, the core of our approach consists in identifying fungal proteins with active sites that are structurally similar, but preferably not identical to binding sites of proteins from the so-called "human pharmacolome". Using structural information from thousands of human protein target-inhibitor complexes, we identified dozens of proteins in fungal species of the genera Histoplasma, Candida, Cryptococcus, Aspergillus and Fusarium, which might be exploited for drug repositioning and, more importantly, also for the design of new fungus-specific inhibitors. As a case study, we present the in vitro experiments performed with a set of selected inhibitors of the human mitogen-activated protein kinases 1/2 (MEK1/2), several of which showed a marked cytotoxic activity in different fungal species.

Histoplasma tympanomastoiditis: Case report and literature review

Histoplasma is a dimorphic fungus capable of producing a diverse array of clinical pathology in humans dependent upon the host immune status. Acute symptomatic infection typically presents as an isolated pulmonary or nodal disease in immunocompetent patients with extra-thoracic manifestations rarely seen in this population. In this report, we describe a novel case of Histoplasma capsulatum tympanomastoiditis in an immunocompetent patient who presented with progressively worsening purulent otorrhea, vertigo, and facial nerve palsy. He was successfully managed with surgical debridement and a prolonged antifungal course.

Clinical Challenges of Emerging and Re-Emerging Yeast Infections in the Context of the COVID-19 Pandemic

During the geological eras, some fungi, through adaptation and/or environmental/ecological pressure, interacted directly and indirectly with humans, through occasionally harmful interaction interdependent on the individual's immunological condition. Infections caused by yeasts are underreported, subjugated, and underdiagnosed, and treatment is restricted to a few drugs, even after the significant progress of medicine and pharmacology. In the last centuries, antagonistically, there has been an exponential increase of immunocompromised individuals due to the use of immunosuppressive drugs such as corticosteroids, increased cases of transplants, chemotherapeutics, autoimmune diseases, neoplasms, and, more recently, coronavirus disease 2019 (COVID-19). This review aims to survey emerging and re-emerging yeast infections in the current clinical context. Currently, there is an immense clinical challenge for the rapid and correct diagnosis and treatment of systemic mycoses caused by yeasts due to the terrible increase in cases in the current context of COVID-19.

Neglected mycobiome in HIV infection: Alterations, common fungal diseases and antifungal immunity

Human immunodeficiency virus (HIV) infection might have effects on both the human bacteriome and mycobiome. Although many studies have focused on alteration of the bacteriome in HIV infection, only a handful of studies have also characterized the composition of the mycobiome in HIV-infected individuals. Studies have shown that compromised immunity in HIV infection might contribute to the development of opportunistic fungal infections. Despite effective antiretroviral therapy (ART), opportunistic fungal infections continue to be a major cause of HIV-related mortality. Human immune responses are known to play a critical role in controlling fungal infections. However, the effect of HIV infection on innate and adaptive antifungal immunity remains unclear. Here, we review recent advances in understanding of the fungal microbiota composition and common fungal diseases in the setting of HIV. Moreover, we discuss innate and adaptive antifungal immunity in HIV infection.

Pathogenicity & Virulence of Histoplasma capsulatum - a multifaceted organism adapted to intracellular environments

Histoplasmosis is a systemic mycosis caused by the thermally dimorphic fungus Histoplasma capsulatum. Although healthy individuals can develop histoplasmosis, the disease is particularly life-threatening in immunocompromised patients, with a wide range of clinical manifestations depending on the inoculum and virulence of the infecting strain. In this review, we discuss the established virulence factors and pathogenesis traits that make H. capsulatum highly adapted to a wide variety of hosts, including mammals. Understanding and integrating these mechanisms is a key step towards devising new preventative and therapeutic interventions.

Updates on Histoplasmosis in Solid Organ Transplantation

Purpose of Review

Recent Findings

Summary

Collective outbreak of severe acute histoplasmosis in immunocompetent Chinese in South America: the clinical characteristics and continuous monitoring of serum cytokines/chemokines

Background

Acute histoplasmosis is a rare fungal disease in China. This study is aimed to summarize the clinical characteristics of the first large-scale outbreak of imported acute histoplasmosis in Chinese, so as to provide suggestions for clinical diagnosis and treatment.

Methods

We collected the symptoms, signs, laboratory examination and imaging data of 10 patients in so far the biggest outbreak of imported acute histoplasmosis in immunocompetent Chinese. Their clinical characteristics and time-varying cytokine/chemokine levels were analyzed, and rank correlation analysis between these markers was utilized to show their condition.

Results

The 10 patients of imported acute histoplasmosis were working without any respiratory protection in an abandoned mine tunnel in Guyana. The most common symptoms were fever and cough. Their chest CT imaging showed multiple nodular shadows in lungs. Laboratory examination showed that at admission the CRP, PCT, LDH, CysC, G-test, β2-MG were all increased in at least 9 patients, and the CD4/CD8 was decreased to < 1 in all patients. Most cytokines/chemokines (other than IL-4, IL-12, INF-α, TNF-α) varied widely with patients and time, but their overall trend is higher at admission and decreasing gradually during hospitalization, especially for the IL-6, IL-8, IL-10 and IFN-γ. The LDH, CysC, G-test, β2-MG, N/L, IL-6, IL-8, IL-10, IFN-γ, IL-27 are in positive associations to both CRP and PCT.

Conclusions

The diagnosis of acute histoplasmosis needs a comprehensive analysis of epidemiological history, clinical symptoms and signs, and results of imaging, laboratory, microbiological and pathological examinations. Although none of the CRP, PCT, G-test, N/L, LDH, CysC, β2-MG, IL-6, IL-8, IL-10, IFN-γ shows specificity in the diagnosis of acute histoplasmosis, there is possibility that the above factors might help in the inflammation and prognosis estimation. However, more studies and further investigation are still required for the verification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12875-022-01771-2.