Pulmonary Aspergillosis

Pulmonary Aspergillosis: Aspergillosis is a common mold that can cause a broad range of pathology but usually affects the lungs. Aspergillus may cause allergic bronchopulmonary aspergillosis (ABPA), chronic necrotizing aspergillus pneumonia, aspergilloma, or invasive aspergillosis. Further, in patients who are immune compromised, Aspergillus may potentially cause endocarditis. ABPA is a hypersensitivity reaction to colonization of Aspergilus in the tracheobronical tree and is most commonly seen in those with cystic fibrosis or asthma. An aspergilloma is a ‘fungus ball’ that develops in a preexisting cavity lesion in the lungs. It is often associated with hemoptysis. Chronic necrotizing aspergillus pneumonia is rare, usually found in immune compromised patients. Invasive aspergillos is a feared and often fatal disease occurring in the severely immune compromised patients. The mortality rate is greater than 30%.

Epidemiology:  Roughly 0.75% of patients with asthma and 7.5% of patients with cystic fibrosis suffer from ABPA. In patients with pre-existing cavitary lung lesions, often due to TB, studies show that nearly 20% may eventually suffer from aspergilloma.

Risk Factors: Immune compromise, cystic fibrosis, asthma

Symptoms:  Each presentation of Pulmonary Aspergillosis manifests in a unique manner. ABPA may cause fever and pulmonary infiltrates that are unresponsive to antibacterial therapy. Invasive aspergillosis may present asan asymptomatic radiographic abnormality at one end of the spectrum tohemoptysis at the other end. In patients who are immune compromised, invasive aspergillosis typically manifests with fever, cough, dyspnea, pleuritic chest pain.

Differential Diagnosis: Tuberculosis, Sarcoidosis, Norcardia, Bronchiectasis, Lung Abscess, Asthma, Acute Respiratory Distress Syndrome

Investigations: Given the many possible presentations, numerous investigations exist. Of note, with aspergilloma the mass is observed the move within the cavity when visualized with chest radiography or CT.

Treatment: ABPA is usually treated with oral corticosteroids. Aspergilloma is ideally treated when possible with surgical resection. Invasive aspergillosis is treated with several anti-fungal medications and if possible also reduction of immunosupression medications/therapy.

Imaging Findings
- Aspergilloma may result in Monad sign, where air may be seen between dependent fungal mass and a lung cavity

- Allergic bronchopulmonary aspergillosis: central bronchiectasis, bronchial wall thickening, and centrilobular nodules
- If bronchial mucus impaction present, characteristic perihilar "gloved-finger" pattern of opacity 

- Chronic necrotizing pulmonary aspergillosis: cavitating nodular opacification and/or consolidation and adjacent pleural thickening

- Invasive pulmonary aspergillosis: early features include poorly defined pulmonary nodular opacities and peripheral wedge-shaped areas of consolidation
- The CT halo sign is a nodular or mass-like lung opacity surrounded by ground glass
- CT halo sign corresponds to a central area of necrosis with surrounding hemorrhage
- Separation of necrotic tissue from adjacent lung results in the air crescent sign
- Air crescent sign a sign of recovery with a favorable prognosis when associated with early institution of treatment
- Complications may arise from invasion of the pleural space resulting in empyema or pneumothorax. 




Case #1. Mycetoma in lung cavity.


 

Case #2. Semi-invasive aspergillosis. CT halo sign (lung nodule with surrounding ground glass opacity) seen in peripheral right lung.




Case #3. Another example of CT halo sign on coronal view.





Case #4. Invasive aspergillosis in a neutropenic patient. Widespread ground glass opacities.