What are the different types of aspergillosis?

Types of Aspergillosis

Aspergillosis encompasses five distinct clinical forms that are determined by the patient's immune status and presence of underlying lung disease: chronic pulmonary aspergillosis (CPA), invasive aspergillosis, allergic bronchopulmonary aspergillosis (ABPA), subacute invasive aspergillosis, and Aspergillus bronchitis. 1

Chronic Pulmonary Aspergillosis (CPA)

CPA occurs in non-immunocompromised patients with prior or current structural lung disease and requires at least 3 months of symptoms for diagnosis. 1 This category includes several subtypes:

Simple Aspergilloma

• A single pulmonary cavity containing a fungal ball with minimal or no symptoms and no radiological progression over at least 3 months. 1
• Requires serological or microbiological evidence of Aspergillus species. 1
• Typically develops in pre-existing cavities from tuberculosis, sarcoidosis, or other chronic lung diseases. 1

Chronic Cavitary Pulmonary Aspergillosis (CCPA)

• The most common form of CPA, characterized by one or more pulmonary cavities (possibly containing aspergillomas) with significant pulmonary and systemic symptoms and overt radiological progression over at least 3 months. 1
• Formerly called complex aspergilloma. 1
• Untreated cavities enlarge and coalesce over years, developing pericavitary infiltrates with raised inflammatory markers. 1

Chronic Fibrosing Pulmonary Aspergillosis (CFPA)

• Severe fibrotic destruction of at least two lobes of lung complicating untreated CCPA, leading to major loss of lung function. 1
• Represents the end-stage progression of CCPA. 1
• Fibrosis appears solid on imaging but may contain large or small cavities with surrounding fibrosis. 1

Aspergillus Nodule

• One or more nodules (<3 cm) that do not usually cavitate, representing an unusual form of CPA. 1
• Can only be definitively diagnosed on histology, as they mimic carcinoma, tuberculoma, or other pathologies. 1
• Tissue invasion is not demonstrated, though necrosis is frequent. 1

Invasive Aspergillosis

Invasive aspergillosis occurs in severely immunocompromised patients (prolonged neutropenia, advanced HIV with CD4+ <100 cells/μL, transplant recipients) and presents as necrotizing pneumonia or tracheobronchitis. 1, 2, 3, 4

• Primary symptoms include fever, cough, dyspnea, chest pain, hemoptysis, and hypoxemia with diffuse, focal, or cavitary infiltrates on imaging. 2
• CT findings include the "halo sign" (ground-glass attenuation) in early disease and "air crescent sign" with cavitation as disease progresses. 2, 3
• Requires histological evidence of tissue invasion by hyphae with positive culture for definitive diagnosis. 2
• Galactomannan testing of serum or bronchoalveolar lavage aids diagnosis. 2

Subacute Invasive Aspergillosis (SAIA)

SAIA, formerly called chronic necrotizing pulmonary aspergillosis, is a more rapidly progressive infection occurring over 1-3 months in mildly to moderately immunocompromised patients. 1

• Variable radiological features include cavitation, nodules, and progressive consolidation with "abscess formation." 1
• Biopsy shows hyphae invading lung tissue. 1
• Positive Aspergillus galactomannan antigen in blood or respiratory fluids. 1
• Should be managed as invasive aspergillosis rather than chronic disease. 1, 4

Allergic Bronchopulmonary Aspergillosis (ABPA)

ABPA occurs almost exclusively in patients with asthma or cystic fibrosis, characterized by an allergic immune response to Aspergillus rather than infection. 3, 4, 5

• Radiographically shows fleeting pulmonary alveolar opacities from immune complex deposition and inflammatory cells. 3
• Mucus plugging and bronchial wall thickening develop over time. 3
• Does not involve tissue invasion. 4, 5

Aspergillus Bronchitis

Aspergillus bronchitis affects patients with bronchial disease such as bronchiectasis, representing colonization and inflammation of airways without tissue invasion. 5

Important Clinical Pitfalls

• The duration criterion of 3 months is critical for distinguishing CPA from invasive or subacute forms—symptoms present for less than 3 months suggest SAIA or invasive disease requiring more aggressive management. 1
• Aspergillus serology (IgG/precipitins) is elevated in over 90% of CPA patients but is typically negative in invasive disease. 1, 6
• The same patient may have overlapping forms of aspergillosis, particularly progression from simple aspergilloma to CCPA to CFPA if untreated. 1