GYNAECOLOGY AND OBSTETRICS
Year : 2005 | Volume
: 15 | Issue : 1 | Page : 89--90
Signs : "Halo sign" in early angioinvasive aspergillus's
S Mahajan, P Nagtode, RR Khandelwal, S Ingole
Imaging Point, Ramdaspeth, Nagpur, India
Consultant Radiologist, Imaging Point, Ramdaspeth, NAGPUR - 440002
|How to cite this article:|
Mahajan S, Nagtode P, Khandelwal R R, Ingole S. Signs : "Halo sign" in early angioinvasive aspergillus's.Indian J Radiol Imaging 2005;15:89-90
|How to cite this URL:|
Mahajan S, Nagtode P, Khandelwal R R, Ingole S. Signs : "Halo sign" in early angioinvasive aspergillus's. Indian J Radiol Imaging [serial online] 2005 [cited 2020 Jul 14 ];15:89-90
Available from: http://www.ijri.org/text.asp?2005/15/1/89/28755
CT appearance of halo of ground glass opacity surrounding focal dense parenchymal nodules or focal area of consolidation in angioinvasive aspergillosis is termed the "Halo sign". We would like to illustrate this with an example.
A young leukemic woman had complaints of cough and chest pain since two months. Plain radiograph revealed focal areas of consolidation mainly in upper zones. CT thorax was done due to non responding nature of infection to routine antibiotic and anti-tubercular trials. CT revealed focal areas of consolidation with air-bronchogram within and surrounding ground-glass opacity, the halo sign. The diagnosis was confirmed on histopathology. Patient responded well to I.V.Amphoterecin.
Aspergillosis is a serious pathologic condition caused by Aspergillus organisms and is frequently seen in immunocompromised patients, most commonly leukemia, lymphoma, with neutropenia, granulocytopenia and absolute neutrophil count <500.. Angioinvasive aspergillosis is the most common form of invasive aspergillosis . Angioinvasive aspergillosis is characterized at histologic analysis by the invasion and occlusion of small to medium-sized pulmonary arteries by fungal hyphae. This leads to the formation of necrotic hemorrhagic nodules or pleural-based, wedge-shaped hemorrhagic infarcts . The clinical diagnosis is difficult, and the mortality rate is high.
Characteristic CT findings consist of nodules surrounded by a halo of ground-glass attenuation ("halo sign") or pleural-based, wedge-shaped areas of consolidation. The halo surrounding the nodule is characteristically lower in attenuation than the nodule itself . Many of these characteristic lesions are associated with vessels. These findings correspond to hemorrhagic infarcts.
Hruban et al  have clarified the etiology of the halo sign. In their patients, the halo and central nodule reflected a rim of coagulation necrosis or hemorrhage surrounding a central fungal nodule or infarct, respectively.
Some authors , have concluded that, in an appropriate population, the CT appearance of early invasive aspergillosis with a visible halo sign is sufficiently characteristic to justify a presumptive diagnosis and treatment . However, a similar appearance has been described in a number of other conditions, including infection by Mucorales and Candida, herpes simplex and cytomegalovirus, Wegener granulomatosis, Kaposi sarcoma and hemorrhagic metastases .
So we would like to conclude that aspergillosis is a serious complication that is frequently seen in immunocompromised patients. The radiologist plays a major role in the diagnosis of early pulmonary Aspergillus infection. When radiographic findings are subtle or equivocal, CT frequently allows identification of the disease process. Although imaging findings in various types of pulmonary aspergillosis may be nonspecific, in the appropriate clinical setting, familiarity with the thin-section CT findings of "halo sign" may suggest and even help establish the specific diagnosis of angioinvasive aspergillosis.
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