Varicella pneumonia is a type of viral pneumonia. It is a common cause of multiple small round calcific lung lesions. Varicella-zoster virus most commonly causes self-limited benign disease (chickenpox) in children. However, in adults it tends to cause significant complications including varicella pneumonia.
Varicella pneumonia is the most serious complication of disseminated varicella-zoster virus infection with mortality rates of 9-50%. More than 90% of cases of varicella-zoster virus pneumonia in adults occur in patients with lymphoma or immune compromise.
Histologic features of varicella-zoster virus pneumonia are those of diffuse alveolar damage. With recovery from the initial disease, spherical nodules are seen, scattered randomly throughout the lung parenchyma.
- multiple 5-10 mm ill-defined nodules that may be confluent and fleeting
- small, round nodules usually resolve within a week after the disappearance of the skin lesions but may persist for months
- lesions can calcify and can persist as numerous, well-defined, randomly scattered, 2-3 mm dense calcifications
- well-defined and ill-defined nodules diffusely throughout both lungs
- nodules with a surrounding halo of ground-glass opacity, patchy ground-glass opacity, and coalescence of nodules are also seen
The differential diagnosis of very dense miliary opacities includes:
- healed varicella pneumonia
- pulmonary haemosiderosis, e.g. mitral stenosis
- repeated haemorrhage, e.g. Goodpasture syndrome
- silicosis: exposure to pure silica
- pulmonary alveolar microlithiasis
- calcified metastases, e.g. osteosarcoma
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