Reactivation of latent Histoplasma and disseminated cytomegalovirus in a returning traveller with ulcerative colitis

Pathophysiology and clinical outcomes of pancytopenia in disseminated histoplasmosis: a scoping review

PURPOSE

Pancytopenia in the setting of disseminated histoplasmosis is sparsely described in the literature. We investigated the underlying mechanisms of pancytopenia in disseminated histoplasmosis and highlighted clinical outcomes.

METHODS

We conducted a scoping review of cases and series on disseminated histoplasmosis presenting with pancytopenia published between 2001 and 2024. PubMed database was used for the search. The search terms were (disseminated histoplasmosis) AND (pancytopenia OR haemophagocytic syndrome OR lymphohistiocytosis).

RESULTS

We identified 72 cases. Forty-four (61.1%) cases were from the Americas, 18 (25.5%) from Asia, 8 (11.1%) from Europe, and 1(1.4%) each from Africa and Australia. Of the 72 cases, five cases (6.9%) were reported in children. The mean age was 41.9 ± 16.7 years with a range of 3 months to 78 years. Seven cases (9.7%) were immunocompetent, 27 (37.5%) had an underlying HIV infection and 45 (62.5%) were complicated with haemophagocytic lymphohistiocytosis syndrome. Histoplasma antigen assay (n = 29, 40.2%) was the major diagnostic method followed by bone marrow biopsy (n = 28, 38.9%). Fifty-three cases (73.6%) recovered, 15 (20.8%) died and outcomes were not stated in 4 cases (5.65%). The relationship between haemophagocytic lymphohistiocytosis and fatal outcomes was not statistically significant (P = 0.5). Likewise, HIV infection was not significantly associated with fatal outcomes (P = 0.6). Fatal outcomes were predominantly due to difficulty or delayed diagnosis of disseminated histoplasmosis and/or haemophagocytic lymphohistiocytosis (n = 5, 6.9%), multiple organ failure (n = 4, 5.6%) and late presentation (n = 2, 2.8%).

CONCLUSION

Pancytopenia in disseminated histoplasmosis is associated with poor outcomes. Such a hematologic finding should arouse the index of suspicion in the attending clinician for an invasive mycosis like disseminated histoplasmosis to avert fatal outcomes. Besides haemophagocytic lymphohistiocytosis, other factors associated with pancytopenia in disseminated histoplasmosis were the cooccurrence of viral and bacterial infections.

Disseminated Histoplasmosis with Underlying Sarcoidosis-Rheumatoid Arthritis Overlap Syndrome: An Example of Diagnostic Test Threshold of Detection Affecting Test Results and Patient Care

Histoplasmosis is common in many parts of the world but with areas of hyperendemicity. Disseminated histoplasmosis is the deadliest form of histoplasmosis and is most common among immunocompromised patients. Timely diagnosis is crucial to improve outcomes. We describe a patient on azathioprine and rituximab with disseminated histoplasmosis in which diagnosis was delayed in part because of negative early Histoplasma antigen testing, which was positive later in the course. This case serves as an example of the concept of “threshold of detection” in which a certain concentration of a microbe must be present for it to be detected by a diagnostic test that focuses on detection of a microbe or its components. This concept applies to many tests used to diagnose infectious diseases.

Kinase Inhibitor Library Screening Identifies the Cancer Therapeutic Sorafenib and Structurally Similar Compounds as Strong Inhibitors of the Fungal Pathogen Histoplasma capsulatum

Histoplasma capsulatum is a dimorphic fungal pathogen endemic to the midwestern and southern United States. It causes mycoses ranging from subclinical respiratory infections to severe systemic disease, and is of particular concern for immunocompromised patients in endemic areas. Clinical management of histoplasmosis relies on protracted regimens of antifungal drugs whose effectiveness can be limited by toxicity. In this study, we hypothesize that conserved biochemical signaling pathways in the eukaryotic domain can be leveraged to repurpose kinase inhibitors as antifungal compounds. We conducted a screen of two kinase inhibitor libraries to identify compounds inhibiting the growth of Histoplasma capsulatum in the pathogenic yeast form. Our approach identified seven compounds with an elongated hydrophobic polyaromatic structure, five of which share a molecular motif including a urea unit linking a halogenated benzene ring and a para-substituted polyaromatic group. The top hits include the cancer therapeutic Sorafenib, which inhibits growth of Histoplasma in vitro and in a macrophage infection model with low host cell cytotoxicity. Our results reveal the possibility of repurposing Sorafenib or derivatives thereof as therapy for histoplasmosis, and suggest that repurposing of libraries developed for human cellular targets may be a fruitful source of antifungal discovery.

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%.