From the Guidelines
Yes, Histoplasma capsulatum can cause a lung mass with hilar adenopathy that is visible on a PET-CT scan. Histoplasmosis is a fungal infection that primarily affects the lungs and can present as a solitary pulmonary nodule or mass, often accompanied by hilar and mediastinal lymphadenopathy. On PET-CT imaging, these lesions typically demonstrate increased FDG uptake, which can mimic the appearance of lung cancer or other malignancies. This occurs because the inflammatory response to the fungal infection causes increased metabolic activity in the affected tissues, resulting in FDG avidity. Histoplasmosis is particularly common in certain geographic regions such as the Ohio and Mississippi River valleys in the United States, where the fungus is endemic in soil. Diagnosis typically requires tissue sampling through bronchoscopy, transthoracic needle aspiration, or surgical biopsy, with subsequent fungal cultures or histopathological examination. Treatment depends on the severity of infection but often includes antifungal medications such as itraconazole (200-400 mg daily for 6-12 weeks) for mild to moderate disease, or amphotericin B followed by itraconazole for severe cases, as recommended by the Infectious Diseases Society of America 1.
Some key points to consider in the management of histoplasmosis include:
- The use of liposomal amphotericin B (3.0 mg/kg daily) for 1–2 weeks, followed by oral itraconazole (200 mg 3 times daily for 3 days and then 200 mg twice daily for a total of at least 12 months) for moderately severe to severe disease 1.
- The importance of monitoring blood levels of itraconazole to ensure adequate drug exposure 1.
- The role of antigen levels in monitoring for relapse during and after therapy 1.
- The potential for immune reconstitution inflammatory syndrome in patients with AIDS, although this is rare and usually not severe 1.
Overall, the management of histoplasmosis requires a comprehensive approach that takes into account the severity of the infection, the patient's underlying health status, and the potential for complications and relapse.
From the Research
Histoplasma Capsulatum Infection
- Histoplasma capsulatum is a fungal organism that can cause systemic histoplasmosis, which may present with a range of symptoms, including lung masses and hilar adenopathy 2, 3.
- The infection can be asymptomatic in healthy immunocompetent individuals, but it can cause severe disease in immunocompromised individuals, particularly those with pre-existing structural lung disease 2, 4.
Imaging Findings
- Imaging findings, such as pulmonary focal infiltrates, cavitary nodules, mediastinal, and hilar lymphadenopathy, are common in histoplasmosis 3, 5.
- A "flip-flop fungus" sign, characterized by greater FDG uptake in draining lymph nodes in comparison with the associated lung nodule, can be seen on [18F]FDG-PET/CT scans, which can help differentiate histoplasmosis from malignant disease 5.
Diagnosis and Treatment
- Diagnosis of histoplasmosis can be challenging, particularly in non-endemic regions, and may require a combination of clinical, laboratory, and imaging findings 5, 6, 4.
- Treatment of histoplasmosis typically involves antifungal therapy, such as itraconazole, and may require long courses of treatment 2, 4.