Imported African histoplasmosis in an immunocompetent patient 40 years after staying in a disease-endemic area

Epidemiological, clinical, diagnostic, and therapeutic features of histoplasmosis: A systematic review

Histoplasmosis is a mycosis due to a dimorphic fungus Histoplasma capsulatum. This study aimed at providing an overview of histoplasmosis epidemiological, clinical, diagnostic, and therapeutic aspects from the last 30 years. This review was carried out using a systematic literature search on histoplasmosis from 1992 to 2021. We describe the clinical features, diagnostic methods and treatment. Empirical searches were conducted via the databases PubMed, Google Scholar and Science Direct. Between 1992 and 2021, 190 manuscripts were published and reported 212 cases of histoplasmosis. These publications included 115 and 97 cases of American and African histoplasmosis respectively. The number of publications increased over the last ten years with a maximum in 2020 (12.34 % of the cases reported). The disseminated forms of histoplasmosis were the most frequently reported cases as compared to the localized forms. This was the case with the American histoplasmosis (75.65 %) as well as with the African histoplasmosis (55.67 %). Itraconazole (31.17 %) and Amphotericin B (26.62 %) were the most used drugs in the management of these cases. American histoplasmosis is distributed worldwide whereas African histoplasmosis is mainly present in intertropical Africa. There is a critical need for setting up a global surveillance system, towards a better understanding of the disease.

Histoplasmosis in Africa: Current perspectives, knowledge gaps, and research priorities

Background

Histoplasmosis is a chronic granulomatous disease caused by the thermally dimorphic fungus Histoplasma capsulatum. The 2 variants Histoplasma capsulatum var. capsulatum (Hcc) and Histoplasma capsulatum var. duboisii (Hcd) causes infection in humans and commonly termed classical or American histoplasmosis and African histoplasmosis, respectively. Histoplasma capsulatum var. farciminosum (Hcf) affects equines. In recent times, there have been heightened sensitization on fungal infections such as histoplasmosis in Africa, aimed at improving awareness among relevant stakeholders, particularly healthcare workers. This effort is expected to be paralleled with increased detection of both classical and African histoplasmosis, which has remained underdiagnosed over the years. In this narrative review, we describe the current perspectives of histoplasmosis in Africa, identify knowledge gaps, and suggest research priorities.

Methods

A PubMed, Google Scholar, and Africa Journal Online (AJOL) literature search was conducted for studies on histoplasmosis in Africa between 2000 and 2020. Histoplasmosis essays in medical mycology textbooks were also consulted. This narrative review was prepared from the data gathered.

Findings

In the past 2 decades, histoplasmosis in general has seen a relative increase in case detection in some Africa countries, probably attributable to the gradually increasing medical mycology advocacy efforts in Africa. Histoplasmosis cases are dominated by African histoplasmosis mostly in Western and Central Africa, while classical histoplasmosis is more common in Southern and Northern Africa. Although both classical and African histoplasmosis are common in Africa, the latter is more restricted to Africa, and cases outside the continent usually have a travel history to the continent. Despite the clinical and laboratory difference between African histoplasmosis and classical histoplasmosis, it is not straightforward to distinguish them. The typical manifestation of African histoplasmosis is the appearance of lesions affecting the skin, bones, and lymph nodes and unusually linked to human immunodeficiency virus (HIV)/AIDS. By contrast, classical histoplasmosis mostly affects the lungs and is often associated with immunosuppression, mainly HIV/AIDS. The present perspectives of histoplasmosis in Africa highlight unclear details on the true burden, strain diversity, infection route and genetic basis of African histoplasmosis, availability of specie-specific diagnostic tools, and compliance with recommended antifungal therapy. These knowledge gaps represent research questions that require scientific exploration.

Conclusions

Despite a subtle increase in identifying histoplasmosis cases in Africa, it remains underdiagnosed and neglected in some parts of the continent. Increasing awareness and training among healthcare workers, bridging diagnostic and therapeutic gaps, and encouraging more research in Africa are crucial to improve the current perspectives of histoplasmosis in Africa.

Histoplasmosis Caused by Histoplasma capsulatum var. duboisii: A Comprehensive Review of Cases From 1993 to 2019

BACKGROUND

Histoplasmosis caused by Histoplasma capsulatum var. duboisii (Hcd) is a rare, but probably underestimated, endemic infection described in intertropical Africa. Therefore, the epidemiology of the infection remains unclear, and there is no consensus on therapeutic management.

METHODS

Using a comprehensive search on different Internet databases, we collected case reports of Hcd infection published from 1993 to 2019. Epidemiological and clinical charts and therapeutic strategies were analyzed.

RESULTS

We found 94 well-documented cases of Hcd infection, and 30.1% of the patients were under 18 years old. Symptoms occurred in some patients several decades after leaving the endemic area. Cutaneous/subcutaneous lesions, bone infections, and lymphadenopathies, both isolated and combined, were the most frequent presentations. The human immunodeficiency virus (HIV) coinfection rate was at 20.8%, with fever, lymphadenopathies, and an absence of bone infection being the differentiating elements from patients living without HIV. The rate of disseminated forms (60.6% in our review) significantly increased as compared to studies published before 1993, but without correlation with HIV infection. The global mortality rate was at 23.4% by the end of follow-up. The outcome was not correlated with the antifungal drug prescribed, nor with HIV serologic status, but was correlated with the initiation of an antifungal therapy.

CONCLUSIONS

Hcd histoplasmosis is a severe fungal infection for which the precise mode of acquisition remains to be determined. There is a need for affordable and more specific diagnostic tools. Itraconazole and amphotericin B are the best therapeutic alternatives and should be available in all low-income countries of the endemic area.

Histoplasmosis Diagnosed in Europe and Israel: A Case Report and Systematic Review of the Literature from 2005 to 2020

Human histoplasmosis is a mycosis caused by two distinct varieties of a dimorphic fungus: Histoplasma capsulatum var. capsulatum and H. capsulatum var. duboisii. In Europe, it is usually imported by migrants and travellers, although there have been some autochthonous cases, especially in Italy; however, most European physicians are unfamiliar with its clinical and pathological picture, particularly among immunocompromised patients without HIV infection. This systematic review of all the cases of histoplasmosis reported in Europe and Israel between 2005 and 2020 identified 728 cases diagnosed in 17 European countries and Israel described in 133 articles. The vast majority were imported (mainly from Central and South America), but there were also seven autochthonous cases (six in Europe and one in Israel). The patients were prevalently males (60.4%), and their ages ranged from 2 to 86 years. The time between leaving an endemic region and the diagnosis of histoplasmosis varied from a few weeks to more than 40 years. Progressive disseminated histoplasmosis was the most frequent clinical picture among people living with HIV infection (89.5%) or a different immunocompromising condition (57.1%), but it was also recorded in 6.2% of immunocompetent patients. Twenty-eight cases were caused by Histoplasma duboisii. Immunocompromised patients without HIV infection had the worst outcomes, with a mortality rate of 32%.

Screening for acute disseminated histoplasmosis in HIV disease using urinary antigen detection enzyme immunoassay: A pilot study in Cameroon

Acute disseminated histoplasmosis (ADH) is an AIDS-defining illness and reported in Cameroon, but there are few data about its incidence. Between June and August 2019, we conducted a descriptive cross-sectional study to screen for histoplasmosis in a population of adults with HIV infection, irrespective of their CD4 T-cell counts, using Histoplasma urine antigen detection enzyme immunoassay (EIA) and histoplasmin skin test. Of the 138 participants screened, 36 (26%) had detectable antigen in urine, using an OD cut off of 0.045. Skin lesions were present in two (6%) cases. Of 39 patients tested for histoplasmin skin test positivity, one was positive. Histoplasma antigenuria was associated with a positive history of chest infection (Odds ratio: 3.632, 95% confidence interval: 1.635-8.071, p= 0.001). As 30 (21.7%) of titres were between 0.045 (the current cut off) and 0.25, the cut off may need adjustment in Cameroon, using disease confirmation with alternative, highly sensitive diagnostic approaches such as PCR and bone marrow examination. H. capsulatum infection appears to be common among HIV-infected patients attending outpatient clinics at the Buea Regional Hospital. There is an acute need to improve awareness and management of HIV patients with respect to H. capsulatum infection.

Timely Diagnosis of Histoplasmosis in Non-endemic Countries: A Laboratory Challenge

Human histoplasmosis is a fungal infection caused by the inhalation of microconidia of the thermally dimorphic fungi Histoplasma capsulatum. Autochthonous cases of histoplasmosis have been diagnosed in almost every country, but it is considered an endemic infection in specific areas of the world. Many of them are popular travel destinations or the source of migratory movements. Thus, the vast majority of the registered cases in non-endemic countries are imported. They correspond to people having been exposed to the fungus in endemic locations as immigrants, expatriates, transient workers or tourists, with reported cases also associated to organ donation. Misdiagnosis and delays in initiation of treatment are not uncommon in cases of imported histoplasmosis. They are associated to high fatality-rates specially in patients with compromised cellular immunity in which progressive disseminated forms develop. The diagnosis of this infection in non-endemic countries is hampered by the lack of clinical suspicion and a dearth of available diagnostic tools adequate to offer rapid and accurate results. Non-culture-based assays such as nucleic-acid amplification tests present as a suitable alternative in this situation, offering improved sensitivity and specificity, shortened turnaround time, and increased biosafety by avoiding culture manipulation. In non-endemic regions, molecular techniques are being used mainly in laboratories from countries that have registered an increase in the incidence of imported cases. However, the number of published techniques is limited and lack consensus. Efforts are currently under way to standardize nucleic acid amplification-based techniques for its implementation in areas registering a rising number of imported cases.

Disseminated histoplasmosis in an immunocompetent individual diagnosed with gastrointestinal endoscopy: a case report

BACKGROUND

Histoplasmosis is one of the invasive fungal infections and presents with symptoms mainly in the lungs. Disseminated histoplasmosis (DH) is rare and its lesions in the gastrointestinal tract are even uncommon. The concomitant involvement of the upper and lower gastrointestinal tract has never been described in the immunocompetent individuals.

CASE PRESENTATION

A 44-year-old immunocompetent Chinese man presented with fever, hepatosplenomegaly, fungal esophagitis and protuberant lesions with central depression and erosion along the mucous membrane of the colon. The patient was diagnosed as disseminated histoplasmosis by gastrointestinal endoscopy.

CONCLUSIONS

Histoplasmosis should be taken caution in patients with fever and hepatosplenomegaly. Actions should be taken to avoid its disseminated infection associated high mortality.

African histoplasmosis in a Guinea Bissau patient with HIV-2: Case report and review

African histoplasmosis is the relatively unknown infection by Histoplasma capsulatum var. duboisii. It is endemic to Central and West Africa, generally involving the skin with potential for systemic dissemination, and has been described mainly in immunocompetent hosts. We present the case of a 30-year-old Bissau-Guinean man with HIV-2 infection known for 16 years, irregularly treated, admitted with two weeks of fever, diarrhoea and cutaneous lesions. Examination revealed multiple subcutaneous nodes, Molluscum contagiosum-like lesions, generalized lymphadenopathy and painful palpation of the left iliac fossa. Laboratory tests showed severe nonhaemolytic anaemia and CD4+ count of 9/mm3, with normal creatinine and hepatic enzymes. Chest roentgenogram was unremarkable and a research for Mycobacterium tuberculosis by GeneXpert® was negative. Nonetheless, given the lack of further diagnostic tools, a presumptive diagnosis of disseminated tuberculosis was made, and the patient was started on tuberculostatic and antiretroviral drugs. Despite initial improvement, a national shortage of antiretrovirals precluded further treatment, with worsening of the clinical picture, namely an increase in the number and dimensions of the skin lesions. An excisional biopsy of a subcutaneous nodule revealed Histoplasma capsulatum var. duboisii. Unfortunately, due to the unavailability of antifungals, the patient died one week later. To our best knowledge, this is the first confirmed case of an HIV infected patient with African histoplasmosis in Guinea-Bissau.

How Environmental Fungi Cause a Range of Clinical Outcomes in Susceptible Hosts

Environmental fungi are globally ubiquitous and human exposure is near universal. However, relatively few fungal species are capable of infecting humans, and among fungi, few exposure events lead to severe systemic infections. Systemic infections have mortality rates of up to 90%, cost the US healthcare system $7.2 billion annually, and are typically associated with immunocompromised patients. Despite this reputation, exposure to environmental fungi results in a range of outcomes, from asymptomatic latent infections to severe systemic infection. Here we discuss different exposure outcomes for five major fungal pathogens: Aspergillus, Blastomyces, Coccidioides, Cryptococcus, and Histoplasma species. These fungi include a mold, a budding yeast, and thermal dimorphic fungi. All of these species must adapt to dramatically changing environments over the course of disease. These dynamic environments include the human lung, which is the first exposure site for these organisms. Fungi must defend themselves against host immune cells while germinating and growing, which risks further exposing microbe-associated molecular patterns to the host. We discuss immune evasion strategies during early infection, from disruption of host immune cells to major changes in fungal cell morphology.

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

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

What, where and why: exploring fluorodeoxyglucose-PET's ability to localise and differentiate infection from cancer

PURPOSE OF REVIEW

To review the utility of FDG-PET imaging in detecting the cause of fever and infection in patients with cancer.

RECENT FINDINGS

FDG-PET has been shown to have high sensitivity and accuracy for causes of neutropenic fever, leading to higher diagnostic certainty in this group. Recent advances in pathogen-specific labelling in PET to identify Aspergillus spp. and Yersinia spp. infections in mice, as well as differentiating between Gram-positive, Gram-negative and mycobacterial infections are promising.

SUMMARY

Patients with cancer are vulnerable to infection and fever, and the causes of these are frequently unclear using conventional diagnostic methods leading to high morbidity and mortality, length of stay and costs of care. FDG-PET/CT, with its unique complementary functional and anatomical information as well as its whole-body imaging capability, has demonstrated use in detecting occult infection in immunocompromised patients, including invasive fungal and occult bacterial infections, as well as defining extent of infection. By demonstrating disease resolution following treatment and allowing earlier cessation of therapy, FDG-PET acts as a key tool for antimicrobial and antifungal stewardship. Limitations include at times poor differentiation between infection, malignancy and sterile inflammation, however, exciting new technologies specific to infectious pathogens may help alleviate that issue. Further prospective randomised research is needed to explore these benefits in a nonbiased fashion.

Histoplasmosis in Africa: An emerging or a neglected disease?

Histoplasmosis in Africa has markedly increased since the advent of the HIV/AIDS epidemic but is under-recognised. Pulmonary histoplasmosis may be misdiagnosed as tuberculosis (TB). In the last six decades (1952-2017), 470 cases of histoplasmosis have been reported. HIV-infected patients accounted for 38% (178) of the cases. West Africa had the highest number of recorded cases with 179; the majority (162 cases) were caused by Histoplasma capsulatum var. dubuosii (Hcd). From the Southern African region, 150 cases have been reported, and the majority (119) were caused by H. capsulatum var. capsulatum (Hcc). There have been 12 histoplasmin skin test surveys with rates of 0% to 35% positivity. Most cases of Hcd presented as localised lesions in immunocompetent persons; however, it was disseminated in AIDS patients. Rapid diagnosis of histoplasmosis in Africa is only currently possible using microscopy; antigen testing and PCR are not available in most of Africa. Treatment requires amphotericin B and itraconazole, both of which are not licensed or available in several parts of Africa.