Current Concepts in the Epidemiology, Diagnosis, and Management of Histoplasmosis Syndromes

Abstract

Histoplasmosis is a global disease endemic to regions of all six inhabited continents. The areas of highest endemicity lie within the Mississippi and Ohio River Valleys of North America and parts of Central and South America. As a result of climate change and anthropogenic land utilization, the conditions suitable for Histoplasma capsulatum are changing, leading to a corresponding change in epidemiology. The clinical manifestations of histoplasmosis are protean, variably resembling other common conditions such as community-acquired pneumonia, tuberculosis, sarcoidosis, Crohn's disease, or malignancy. Making a successful diagnosis is contingent on a thorough understanding of epidemiology, common clinical presentations, and best testing practices for histoplasmosis. While most subclinical or self-limited diseases do not require treatment in immunocompetent patients, all immunocompromised patients and those with progressive disseminated disease or chronic pulmonary disease should be treated. Liposomal amphotericin B is the preferred agent for severe or disseminated disease, while itraconazole is adequate for milder cases and “step-down” therapy following response to amphotericin B. In this review, we discuss the current evidence-based approaches to the epidemiology, diagnosis, and management of histoplasmosis.

Gastrointestinal Histoplasmosis Mimicking Crohn’s Disease

“…There are currently 3 methods to detect H. capsulatum –specific antibodies: complement fixation (CF), immunodiffusion (ID), and EIA. The standard serologic tests for histoplasmosis include CF and ID assay [ 19 ]. The ID assay is more sensitive than CF testing.…”

“…The M band develops with acute infection and may persist for years after clinical improvement. However, the H band is seen most often in patients with chronic, disseminated, and progressive histoplasmosis [ 19 ]. CF, using yeast antigen, is the most sensitive serologic assay, while ID assay is a more specific test.…”

Climate change and the emergence of fungal pathogens

“…While this predates the era of significant climate change, it demonstrates the ramifications of acute environmental disruption, particularly as climate change modelling predicts that the range of Coccidioides could expand from 12 to 17 states, with infections increasing by 50% [ 41 ] Apophysomyces trapeziformis , a thermotolerant saprotroph that is an extremely rare cause of mucormycosis caused a cluster of cases in patients wounded following the 2011 tornado in Joplin, Missouri [ 42 ]. Various other soil-borne fungal pathogens have been speculated to have increased in frequency or range due to climate-induced disruptions, including Talaromyces marneffei [ 43 ], Blastomyces , Histoplasma [ 44 ], and Paracoccidioides [ 45 ]. Outside of their normal range, these fungal infections can be challenging to diagnose and they are often refractory to treatment, frequently resulting in poor patient outcomes [ 40 ].…”

High prevalence and mortality due to Histoplasma capsulatum in the Brazilian Amazon: An autopsy study

“…H. capsulatum infections in immunocompetent individuals are typically asymptomatic or are associated with mild symptoms, but can cause severe disease in patients exposed to a large inoculum of the fungus [7]. In contrast, immunocompromised patients, especially HIV-positive individuals, are much more likely to develop a disseminated infection [8].…”