Clinical History
A 48-year-old man with Acute Myelomonocytic Leukaemia (AML) was evaluated for fever and melaena.
Imaging Findings
A 48-year-old man with AML developed severe neutropenia, fever and melaena after the first cycle of chemotherapy. A chest radiograph showed multiple bilateral, patchy, nodular opacities and left pleural effusion. Chest computed tomography (CT) confirmed a multifocal involvement of the lung parenchyma, characterized by multiple and bilateral cavitatory lesions, mainly distributed in the upper lobes. Some lesions contained hyperdense nodules, which were separated from the lesion walls by an air space (the ‘air crescent’ sign). The nodules appeared to be surrounded by a ground-glass attenuation area (the CT 'halo' sign). Bilateral pleural effusion was also present. These signs were suggestive for invasive pulmonary aspergillosis.
An abdominal CT scan revealed a bowel subocclusion with significant wall thickening of some bowel loops, which was interpreted as a possible consequence of the mycotic infection. A few days later, the patient developed oral cavity mucositis and obstructive nasal symptoms. A brain and maxillo-facial CT revealed an involvement of the right ethmoidal sinus and of the maxillary sinuses, as well as an erosion of the palatine bones, the right lacrimal bone, and the right frontal and palatine processes of the maxilla, associated with involvement of right medial periorbital soft tissues. Nine days later, during the antimycotic treatment, a new chest and abdominal CT examination was performed, revealing imaging findings compatible with an initial improvement. In particular, the exam showed a numerical and dimensional decrease of the bilateral cavitatory pulmonary lesions, as well as a reduction of pleural effusion decrease and total resolution of bowel subocclusion.
Discussion
Invasive aspergillosis is a potentially lethal opportunistic infection that primarily occurs in immunosuppressed patients, like patients with hematologic disorders (leukaemia, lymphoma) and those who have undergone bone marrow or other organ transplantation. Specifically, invasive aspergillosis should be suspected in any patient with neutropenia who develops fever not responding to antibiotics. Owing to its intrinsic high mortality rate, early diagnosis and treatment are essential for a successful clinical outcome in these patients. A tissue diagnosis may be difficult, because sputum cultures are positive in only 10% of patients. Alternatively, more invasive diagnostic approaches, including bronchoscopy with transbronchial biopsy, percutaneous needle aspiration biopsy, or open lung biopsy, may be required. However, possible thrombocytopenia or compromised respiratory status may be a relative contraindication to these invasive procedures. For these reasons, imaging findings that suggest the diagnosis of invasive aspergillosis are important.
Initially, in the invasive pulmonary aspergillosis, chest radiograph may be normal, but as the infection progresses, single or multiple rounded opacities, pleural-based infiltrates (pulmonary infarctions) and cavitation can develop. In the early stages of infection, CT is more sensitive and specific than radiography. Typical chest CT scan findings are multiple nodules, the halo sign (zone of low attenuation due to haemorrhage surrounding the pulmonary nodule) and the air crescent sign (crescent-shaped lucency secondary to necrosis) that marks the recovery phase of the infection. Extensive paranasal sinus involvement is frequently associated with disseminated aspergillosis. In this particular involvement, CT scan can show focal or diffuse areas of increased attenuation in paranasal sinus. CT and MRI can also demonstrate invasive processes of the skull base and the facial bones, defining periorbital and intracranial spread. Moreover, the gastrointestinal tract can be affected by aspergillosis. In this site, aspergillosis can cause bowel infarction or diffuse peritonitis from a small bowel perforation. Findings of abdominal CT such as small bowel obstruction secondary to segmental mural thickening, diffuse small bowel distention, and inflammation of the peri-enteric fat, may be non-specific.
The gold standard of systemic antimycotic treatment is voriconazole, which has proved to be significantly superior to conventional amphotericin B. Combined therapy with two antimycotic compounds may be a promising future strategy for first-line treatment.
Differential Diagnosis List