Organizing pneumonia as a pulmonary sequela of swine flu.

Comments on: Pulmonary sequelae in a patient recovered from swine flu

Sir,

We read with great interest the case reported by Singh, et al.,[1] who described pulmonary sequelae in a 29-year-old female patient who had recovered from swine flu (H1N1 influenza). The patient presented initially with ground-glass opacities detected by computed tomography (CT), and developed interstitial lung disease after recovery. The authors discussed the long-term consequences of swine flu, especially the development of pulmonary fibrosis. Subsequently, Joob, et al.[2] commented on the observations of Singh, et al.[1] and suggested that the long-lasting presentation in patients with swine flu could be due to the presence of concomitant underlying pulmonary disease or the possible role of swine flu infection in the deterioration of concomitant cardiovascular disease.

Recently, Lee, et al.[3] reviewed serial CT findings from patients with influenza A (H1N1) virus infection. They concluded that the lesions observed on initial CT scans tended to resolve to fibrosis, which then resolved completely or displayed substantially reduced residual disease. They also suggested that the pathophysiological mechanism underlying lung fibrotic changes caused by H1N1 might differ from those of other lung diseases and the patients with H1N1 and lung fibrotic changes were capable of self-rehabilitation. Histopathological studies have shown that these later changes are due to secondary organizing pneumonia (OP) in most cases.[4-8]

This issue is very important because pulmonary fibrosis observed in the recovery phase may, at least in part, account for the respiratory symptoms observed in these patients. The diagnosis of secondary OP after H1N1 infection is important because proper treatment of OP requires corticosteroid therapy. Physicians should be aware that OP may complicate the recovery of patients with H1N1 infection, and the development of late opacities observed on CT scans during recovery should suggest this diagnosis.[478]