Description

• A spectrum of diseases caused by species of the ubiquitous mold, Aspergillus
  • Saprophytic: chronic pulmonary aspergillosis (CPA), aspergilloma, chronic cavitary, chronic fibrosing, chronic necrotizing pulmonary aspergillosis (CNPA)
  • Allergic: allergic bronchopulmonary aspergillosis (ABPA), Aspergillus hypersensitivity (AH)
  • Invasive: invasive aspergillosis (IA)
• Infection usually involves the lungs and sinuses; GI, ophthalmologic, CNS, and skin less common

Epidemiology

• Aspergillus spp. are ubiquitous, distributed worldwide, found in decomposing plant matter.
• Affects patients of all ages, no gender predominance
• CPA typically involves older patients with structural pulmonary abnormalities.
• Chronic obstructive pulmonary disease (COPD) and tuberculosis increase risk of CPA.

Incidence

• Aspergillosis is the most frequent invasive fungal infection in hematopoietic stem cell transplantation (HSCT) patients.
• ABPA incidence is 1–4% in patients with asthma and 7–9% in patients with cystic fibrosis (CF).
• IA incidence in allogeneic and autologous HSCT is 2–15% and 0.5–4%, respectively.
• IA incidence may be as high as 6% in ICU patients, many of whom lack classic risk factors.
• Cutaneous involvement in 1% of IA; most patients have underlying hematologic malignancies.

Prevalence

• ABPA prevalence is 13% in asthma.
• CPA prevalence is <1 in 100,000 in the United States; higher in Asia and Africa

Etiology and Pathophysiology

• Inhalation is the most common route of entry for Aspergillus spores.
• ABPA results from an exaggerated immune response. Milder responses can result in AH.
• Aspergillomas form within existing lung cavities when spores germinate and create mass of hyphae.
• Alveolar macrophages are the first line of phagocytic host defense against Aspergillus sp. Neutrophils are the predominant immune defense against hyphae (explaining the high risk of IA in neutropenic patients).
• Aspergillus fumigatus is responsible for most clinically significant disease (>67%); Aspergillus flavus, Aspergillus niger, and Aspergillus terreus also pathogenic
• Cutaneous manifestations may result from direct inoculation or systemic spread of invasive disease.

Risk Factors

• Patients with atopy, asthma, and CF are at greatest risk for developing AH and ABPA.
• All patients with asthma should be routinely screened for ABPA using A. fumigatusspecific IgE levels.
• CPA occurs primarily in patients with structural lung disease (COPD, cavitary tuberculosis, bronchiectasis, sarcoidosis, or bronchocentric carcinoma), particularly patients treated with high-dose corticosteroids.
• IA is an opportunistic infection found in severely immunocompromised hosts.
  • Neutropenia predisposes patients to IA, particularly if severe (<100 cells/μL), prolonged (>10 days), or associated with aplastic anemia, current chemotherapy, leukemia, solid organ transplant, or HSCT. Highest risk is in HSCT, lung transplantation, and congenital or acquired immunodeficiency syndromes.
  • Genetic deficiency of receptor pentraxin 3 (PTX3, affects neutrophil antifungal activity) may increase risk for IA after HSCT.
  • Patients on long-term steroids or anti-TNF agents are at risk of IPA.

General Prevention

• Treat preexisting lung disease.
• Prophylaxis with posaconazole reduces risk of IA in highest risk patients, including allogeneic HSCT recipients with graft-versus-host disease (GVHD) and neutropenic patients with acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) who are receiving chemotherapy.