Updates on Histoplasmosis in Solid Organ Transplantation

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.

A Systematic Literature Review to Determine Gaps in Diagnosing Suspected Infection in Solid Organ Transplant Recipients

Background

Improved diagnostic testing (DT) of infections may optimize outcomes for solid organ transplant recipients (SOTR), but a comprehensive analysis is lacking.

Methods

We conducted a systematic literature review across multiple databases, including EMBASE and MEDLINE(R), of studies published between 1 January 2012-11 June 2022, to examine the evidence behind DT in SOTR. Eligibility criteria included the use of conventional diagnostic methods (culture, biomarkers, directed-polymerase chain reaction [PCR]) or advanced molecular diagnostics (broad-range PCR, metagenomics) to diagnose infections in hospitalized SOTR. Bias was assessed using tools such as the Cochrane Handbook and PRISMA 2020.

Results

Of 2362 studies, 72 were eligible and evaluated heterogeneous SOT populations, infections, biospecimens, DT, and outcomes. All studies exhibited bias, mainly in reporting quality. Median study sample size was 102 (range, 11-1307). Culture was the most common DT studied (N = 45 studies, 62.5%), with positive results in a median of 27.7% (range, 0%-88.3%). Biomarkers, PCR, and metagenomics were evaluated in 7, 19, and 3 studies, respectively; only 6 reported sensitivity, specificity, and positive/negative predictive values. Directed-PCR performed well for targeted pathogens, but only 1 study evaluated broad-range PCR. Metagenomics approaches detected numerous organisms but required clinical adjudication, with too few studies (N = 3) to draw conclusions. Turnaround time was shorter for PCR/metagenomics than conventional diagnostic methods (N = 4 studies, 5.6%). Only 6 studies reported the impact of DT on outcomes like antimicrobial use and length of stay.

Conclusions

We identified considerable evidence gaps in infection-related DT among SOT, particularly molecular DT, highlighting the need for further research.

High histoplasmosis incidence in kidney transplant recipients in Santa Fe city, Argentina

Histoplasmosis is endemic in the central/northeast region of Argentina. It is estimated that the incidence of this mycosis is low in solid organ transplant recipients. This work aims to describe the epidemiology, clinical forms, and evolution of kidney transplant recipients diagnosed with histoplasmosis in Santa Fe city, Argentina. A retrospective study was carried out between 2015 and 2020 on kidney transplant patients with symptoms associated with histoplasmosis in Santa Fe. Histoplasmosis diagnosis was performed through histopathology, recovery of Histoplasma spp., by culture, and/or positive nested Polimerase Chain Reaction (PCR) specific for the Histoplasma Hc100 gene. During the study period, 360 kidney transplantations were performed. Of these patients, 12 were diagnosed with histoplasmosis (3.3%). The patients' median age was 51 years, and 75% were male. Eleven patients (92%) presented the disseminated form of the disease. Thirty-three percent were diagnosed with histoplasmosis in their first year post-transplantation (mostly 6-12 months), while 42% received their diagnosis 3 years after transplantation. Laboratory diagnosis was performed by histopathology, culture, and PCR in four cases (33%), by culture and PCR in three cases (25%), and by PCR alone in three cases (25%). Thus, all 12 patients showed positive nested PCR results. All patients received amphotericin B as initial treatment. A good response was observed in 83% of patients. We found a high incidence of histoplasmosis in kidney transplant recipients (up to 10 times higher than reports from other endemic areas). Diagnosis by histopathology/culture showed 75% sensitivity, while nested PCR showed better sensitivity and diagnostic speed.

The pre-transplant evaluation: Considerations for trainees and early career transplant infectious diseases clinician

Transplant infectious disease (TID) clinicians are integral to the pre-transplantation evaluation. Pre-transplant evaluations allow clinicians to assess risk factors for latent infections and relevant exposures to potential pathogens, address immunizations, and optimize patients' health and understanding of life after transplant. However, there is not a standardized approach to the pre-transplant evaluation. This article reviews the details of performing successful pre-transplant evaluations, including updated recommendations on available vaccines and contemporary opinions on marijuana use. This resource can be used for teaching with trainees or for early career TID clinicians.

Histoplasma capsulatum urinary antigen detection in a kidney transplant recipient with acute paracoccidioidomycosis: Case study and literature review

BACKGROUND

Paracoccidioidomycosis (PCM) and histoplasmosis are endemic fungal diseases in South America. Both can lead to lung involvement with fungal dissemination progressing to systemic and severe clinical manifestations, especially in immunosuppressed hosts. As the population of immunosuppressed individuals has been rising, a higher occurrence of fungal infections is predicted in this setting. This poses challenges regarding the differential diagnosis due to overlapping clinical and laboratorial findings, hampering the management of cases.

OBJECTIVES

In this study, the authors discuss the occurrence of a false-positive Histoplasma urinary antigen detection in a kidney transplant recipient with acute PCM. Given the scarce information about this subject, a review on literature data is provided.

METHODS

A comprehensive literature search was conducted to investigate previous studies that found cross-reactivity between Histoplasma urinary antigen assays in human patients with confirmed diagnosis of PCM. Additionally, an update of PCM in transplant recipients is provided.

FINDINGS

The included studies reported 120 samples from patients with PCM tested for Histoplasma antigen, presenting an overall cross-reactivity of 51.67% and 17 cases of PCM in transplant recipients. CONCLUSIONS: The galactomannan urinary antigen developed to diagnose histoplasmosis can cross react with PCM, which may represent a concern in countries where both mycoses overlap.

Disseminated Histoplasmosis in a Patient with Myelofibrosis on Ruxolitinib: A Case Report and Review of the Literature on Ruxolitinib-Associated Invasive Fungal Infections

Ruxolitinib, a selective inhibitor of Janus kinases, is a standard treatment for intermediate/high-risk myelofibrosis (MF) but is associated with a predisposition to opportunistic infections, especially herpes zoster. However, the incidence and characteristics of invasive fungal infections (IFIs) in these patients remain uncertain. In this report, we present the case of a 59-year-old woman with MF who developed disseminated histoplasmosis after seven months of ruxolitinib use. The patient clinically improved after ten weeks of combined amphotericin B and azole therapy, and ruxolitinib was discontinued. Later, the patient received fedratinib, a relatively JAK2-selective inhibitor, without relapse of histoplasmosis. We also reviewed the literature on published cases of proven IFIs in patients with MF who received ruxolitinib. Including ours, we identified 28 such cases, most commonly due to Cryptococcus species (46%). IFIs were most commonly disseminated (39%), followed by localized lung (21%) infections. Although uncommon, a high index of suspicion for opportunistic IFIs is needed in patients receiving JAK inhibitors. Furthermore, the paucity of data regarding the optimal management of IFIs in patients treated with JAK inhibitors underscore the need for well-designed studies to evaluate the epidemiology, pathobiology, early diagnosis, and multimodal therapy of IFIs in patients with hematological malignancies receiving targeted therapies.

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.

Evaluation of Five Non-Culture-Based Methods for the Diagnosis of Meningeal Sporotrichosis

Sporotrichosis is the main subcutaneous mycosis worldwide. Several complications, including meningeal forms, can be observed in immunocompromised individuals. The sporotrichosis diagnosis is time-consuming due to the culture's limitations. The low fungal burden in cerebrospinal fluid (CSF) samples is another important drawback in the diagnosis of meningeal sporotrichosis. Molecular and immunological tests can improve the detection of Sporothrix spp. in clinical specimens. Therefore, the following five non-culture-based methods were evaluated for the detection of Sporothrix spp. in 30 CSF samples: (i) species-specific polymerase chain reaction (PCR); (ii) nested PCR; (iii) quantitative PCR; (iv) enzyme-linked immunosorbent assay (ELISA) for IgG detection; and (v) ELISA for IgM detection. The species-specific PCR was unsuccessful in the diagnosis of the meningeal sporotrichosis. The other four methods presented substantial levels of sensitivity (78.6% to 92.9%) and specificity (75% to 100%) for the indirect detection of Sporothrix spp. Both DNA-based methods presented similar accuracy (84.6%). Both ELISA methods were concomitantly positive only for patients with sporotrichosis and clinical signs of meningitis. We suggest that these methods should be implemented in clinical practice to detect Sporothrix spp. in CSF early, which may optimize treatment, augment the chances of a cure, and improve the prognosis of affected individuals.

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.