Histoplasmosis: An epidemiological and clinical update in China, review and a case report

Abstract

Histoplasmosis is a systemic mycosis caused by the dimorphic fungus in the genus Histoplasma. Histoplasmosis is overlooked in China. This study aims to provide an epidemiological and clinical update on histoplasmosis in China by literature review. We reviewed cases of histoplasmosis reported in recent 11 years and described a case of histoplasmosis-triggered hemophagocytic lymphohistiocytosis (HLH) in an immunocompetent patient. A total of 225 cases of histoplasmosis diagnosed in China between 2012 and 2022 were involved in this study, compared with 300 cases reviewed from 1990 to 2011, an increasing number of cases of histoplasmosis have been diagnosed in the last 11 years. The majority of cases of histoplasmosis were autochthonous cases, mainly from provinces Sichuan (56/225, 24.9%), Hunan (50/225, 22.2%), Guangdong (31/225, 13.8%), and Yunnan (24/225, 10.7%). Higher incidence (52.5%, 53/99) of histoplasmosis occurred in immunocompetent patients which is similar to those from the previous 21 years, and the prevalence of the disease did not vary highly over time. Of note, the number of histoplasmosis cases is increasing, and the geographic distribution is shifting southwards over time. Improved awareness is critically important for informing clinical practice in China.

Keywords: China; Histoplasma capsulatum; Histoplasmosis; epidemiology; hemophagocytic lymphohistiocytosis.

Figure 1.

A CT scan of chest and abdomen on the day of admission. A mild inflammation was seen in the lower lobes of bilateral lungs, and the liver was slightly enlarged.

Figure 2.

Histoplasma capsulatum (numerous, capsulated yeast cells) of phagocyte cells (arrow) in bone marrow smear (Wright’s staining, magnification 1,000×).

Figure 3.

(a, b) Yeast-like spores and hyphae (with an arrow, gram staining, magnification 1,000×) under microscopy with bone marrow cultured at 37 °C in 16 days. (c, d) Colonies grown at 28 °C and 37 °C with bone marrow bone cultured in 16 days; (c) White, short villous and filamentous colonies; (d) Yeast-like colonies. (e, f) Fungal morphology under microscopy by taking colonies, respectively; (e) A filamentous form with tuberculate macroconidia on the septate hyphae (lactic acid phenol cotton blue staining); (f) Yeast-like fungus, budding cells with pseudohyphae (gram staining).

Figure 4.

Modified PRISMA flow chart.

Figure 5.

The geographical distribution of histoplasmosis diagnosed in southern China during 2012–2022 compared to those during 1990–2011.