Follicular Bronchiolitis

Clinical History

A 40 year old male patient presented at the pulmonary medicine department with worsening dyspnoea. Until admission the diagnosis of recurrent atypical pneumonia was made and he had received treatment with various antibiotics. On admission he showed a partial ventilatory insuffiency and there were marked restrictive changes at lung function.

Imaging Findings

The initial radiograph showed marked interstitial changes associated with low lung volumes (Fig. 1). A chest high resolution computed tomography (HRCT) examination with a slice thickness of 1 mm was further indicated. The most characteristic HRCT finding were disseminated centrilobular micronodules of ground-glass opacity. There were also well defined areas of air-trapping and geographic areas of ground-glass opacity. There were no findings consistent with fibrosis and there were no consolidations (Fig. 2, 3). For further diagnosis a video assisted thoracoscopic biopsy (VATS) was performed and histologic specimens were obtained. On pathology the most prominent finding was follicular bronchiolitis. There were also slight changes consistent with fibrosing alveolitis. Consequently the diagnosis of follicular bronchiolitis, presumably caused by a hypersensitivity reaction, was established. Postoperatively the patient recovered well and symptoms improved with cortisone medication.

Discussion

Follicular bronchiolitis is characterised by a reactive hyperplasia of the pulmonary lymphoid system. Histologically a typical polyclonal hyperplasia of lymphoid tissue around bronchioles is found [1]. Follicular bronchiolitis is most often associated with connective tissue diseases, immunodeficiency, pulmonary infections or hypersensitivity reactions. It can also be idiopathic [1, 2]. Most patients present with progressive dyspnoea, like in our case [2]. HRCT is the imaging evaluation of choice. In their study of CT findings of 12 patients with histologically proven follicular bronchiolitis Howling et al. found that disseminated centrilobular nodules were the prominent finding and were present in all patients, while further peribronchial nodules and ground glass opacities could not be found in every case [1]. The typical centrilobular nodules of ground-glass opacity were also be found in our case. Coexistent slight fibrotic changes may point to an underlying disease like lung involvement in autoimmune diseases or an exogenous allergic alveolitis. In these cases, treatment should be directed to the underlying disease. In idiopathic cases however, treatment consists mainly of bronchodilatators and cortisone [2].

Differential Diagnosis List

Final Diagnosis

Follicular bronchiolitis

URL:	https://www.eurorad.org/case/9374
DOI:	10.1594/EURORAD/CASE.9374
ISSN:	1563-4086