Chronic Cavitary Pulmonary Histoplasmosis-Novel Concepts Regarding Pathogenesis.

Area of Science:

• Pulmonary Medicine
• Infectious Diseases
• Immunology

Background:

• Chronic cavitary histoplasmosis (CCPH) often affects lung apices, leading to assumptions of pathogenesis similar to tuberculosis.
• However, the characteristic caseation in tuberculosis is unusual in CCPH.
• Chronic obstructive pulmonary disease (COPD) is common and features apical bullae, but CCPH is rare, leaving its pathogenesis unclear.

Purpose of the Study:

• To investigate the pathogenesis of CCPH by analyzing cellular infiltrates.
• To compare the cellular profile of CCPH with assumed tuberculous pathogenesis.
• To establish a baseline for future studies on CCPH immune responses.

Main Methods:

• Histochemical stains were used to identify T cells, B cells, plasma cells, and macrophages in a CCPH patient's lung tissue.
• Immunohistochemical analysis was performed on a cellblock from a patient with CCPH.

Main Results:

• The study suggests CCPH pathogenesis involves repeated colonization of lung bullae by Histoplasma capsulatum propagules in individuals with COPD from endemic areas.
• This contrasts with the caseous liquefaction seen in tuberculosis.
• Immunohistochemical analysis of cellular components in CCPH was performed for the first time.

Conclusions:

• The pathogenesis of CCPH likely involves repeated fungal colonization of bullae in COPD patients, differing from tuberculosis.
• Further research is needed to identify macrophage subtypes and cytokines to understand the inflammatory nature of CCPH.