What is the likely source of Histoplasma capsulatum infection in an 85-year-old woman with rheumatoid arthritis taking a Tumor Necrosis Factor (TNF) alpha inhibitor, who developed severe respiratory symptoms after visiting her grandchildren?

From the Guidelines

The likely source of Histoplasma capsulatum infection in this 85-year-old woman with rheumatoid arthritis taking a TNF-alpha inhibitor is exposure to bird or bat droppings, particularly if her grandchildren's home is in an endemic area such as the Ohio or Mississippi River valleys. The fungus thrives in soil contaminated with these droppings, and activities that disturb the soil can aerosolize the spores, leading to inhalation. Her immunocompromised state due to both advanced age and the TNF-alpha inhibitor therapy (such as infliximab, etanercept, or adalimumab) significantly increases her risk of developing severe histoplasmosis rather than the mild or asymptomatic infection that might occur in immunocompetent individuals. The respiratory symptoms are consistent with pulmonary histoplasmosis, which can be particularly severe in immunocompromised patients. TNF-alpha plays a crucial role in granuloma formation and maintenance, which is an important defense mechanism against fungal pathogens like Histoplasma. When this pathway is blocked by medication, the body's ability to contain the infection is compromised, allowing for dissemination and more severe disease manifestations, as noted in the guidelines for the management of patients with histoplasmosis 1.

Some key points to consider in this case include:

• The patient's age and immunocompromised state increase her risk of severe histoplasmosis
• The patient's symptoms, such as severe shortness of breath, cough, and chest pain, are consistent with pulmonary histoplasmosis
• The patient's TNF-alpha inhibitor therapy may have increased her risk of developing severe histoplasmosis
• The endemic area of the Ohio or Mississippi River valleys is a common location for Histoplasma capsulatum infection, as noted in the guidelines for the management of patients with histoplasmosis 1.

Given the patient's symptoms and medical history, it is likely that she acquired the infection through exposure to bird or bat droppings in an endemic area, and the most likely source of the infection is her grandchildren's home in an endemic area. This is supported by the fact that Histoplasma capsulatum is commonly found in soil contaminated with bird or bat droppings, and that activities that disturb the soil can aerosolize the spores, leading to inhalation, as noted in the guidelines for the management of patients with histoplasmosis 1.

In terms of treatment, the guidelines recommend that patients with severe or moderately severe acute pulmonary, chronic pulmonary, disseminated, and CNS histoplasmosis should receive treatment, and that the treatment of choice for chronic pulmonary histoplasmosis is itraconazole, 200 mg once or twice daily for 12–24 months, as noted in the guidelines for the management of patients with histoplasmosis 1. Additionally, the guidelines recommend that patients with diffuse pulmonary histoplasmosis should receive amphotericin B, 0.7 mg/kg/d, or one of the lipid preparations at a dose of 3 mg/kg/d for patients with renal impairment, as noted in the guidelines for the management of patients with histoplasmosis 1.

Overall, the patient's symptoms and medical history suggest that she has developed severe histoplasmosis due to her exposure to bird or bat droppings in an endemic area, and that she should receive treatment with itraconazole or amphotericin B, depending on the severity of her symptoms, as noted in the guidelines for the management of patients with histoplasmosis 1.

From the Research

Likely Source of Infection

The patient's symptoms and test results suggest that she has contracted histoplasmosis, a fungal infection caused by inhaling spores of Histoplasma capsulatum. The likely source of this infection can be considered based on the following factors:

• The patient's recent visit to her grandchildren
• Her residence in Gainesville, Florida
• The endemic areas of Histoplasma capsulatum

Endemic Areas of Histoplasma capsulatum

According to the studies 2, 3, 4, Histoplasma capsulatum is commonly found in the Ohio River and Mississippi River valleys, where the soil is enriched with bird droppings and bat guano. However, the fungus can be found in other areas as well, including outside of its traditionally recognized endemic regions 3.

Possible Exposure Sources

Given the patient's residence in Gainesville, Florida, and her recent visit to her grandchildren, the possible sources of exposure can be considered:

• Visiting a chicken coop in Texas (A) is unlikely, as there is no mention of the patient traveling to Texas.
• Participating in an archeologic dig in Ohio (B) is possible, as Ohio is within the endemic area of Histoplasma capsulatum, but there is no mention of the patient participating in such an activity.
• Being caught in a dust storm while on a hike in Arizona (C) is unlikely, as Arizona is not typically considered an endemic area for Histoplasma capsulatum.
• Going hiking through a Eucalyptus tree forest in Australia (D) is unlikely, as Australia is not considered an endemic area for Histoplasma capsulatum, and there is no mention of the patient traveling to Australia.
• Beginning to volunteer in a nursing home in Gainesville, Florida (E) is unlikely to be the source of exposure, as nursing homes are not typically associated with Histoplasma capsulatum.

Most Likely Source

Based on the information provided, the most likely source of the patient's infection is not explicitly stated in the options. However, given the patient's recent visit to her grandchildren, it is possible that she was exposed to contaminated soil or dust during this visit, potentially in an area with bird or bat activity 2, 3, 4.