Follicular Bronchiolitis

distribution. A genetic susceptibility has been well documented over the years and has been identified as a human leukocyte antigen (HLA)-associated major susceptibility gene [26].

Symptoms and Signs

Common symptoms of DPB are persistent cough, large amount of purulent sputum, and progressive exertional dyspnea [27]. Wheezing and crackles are heard. Superimposed pneumonia can occur. More than 80 % of patients have a history or coexistence of chronic paranasal sinusitis.

CT Findings

The characteristic TSCT findings include centrilobular small nodules and branching linear opacity lesions, bronchiolectasis, bronchiectasis, and mosaic areas of decreased parenchymal attenuation [10] (Fig. 18.6). The presence of these findings is related to the stage of disease: the earliest manifestation consists of centrilobular small nodules, followed by branching opacity lesions that connect to the nodules, followed by bronchiolectasis and, eventually, bronchiectasis. Cystic bronchiectasis may be seen in the late stage [28]. The nodular bronchiectatic form of nontuberculous mycobacterial lung disease and DPB shows similar imaging findings. However, the number of lobes involved with bronchiectasis and cellular bronchiolitis on TSCT are more numerous in DPB patients [29].

CT–Pathology Comparisons

TSCT findings of centrilobular small nodules and branching linear opacity lesions, bronchiolectasis, and bronchiectasis have been shown to correspond to bronchiolar wall and peribronchiolar inflammation and fibrosis, bronchiolar dilatation with the presence of intraluminal secretions, and dilated airfilled bronchioles. Mosaic areas of decreased parenchymal attenuation are related to air trapping caused by bronchiolar narrowing in the subpleural areas [10].

Patient Prognosis

Long-term low-dose erythromycin therapy is effective for DPB with a 5-year survival rate of 91 % [30]. Prognosis is poor in the advanced cases with extensive bronchiectasis or respiratory failure.

Follicular Bronchiolitis

Pathology and Pathogenesis

Follicular bronchiolitis is characterized by lymphoid follicles containing reactive germinal centers in the walls of bronchioles and occasionally pleura, especially in patients with rheumatoid arthritis (Fig. 18.7). There may be postobstructive changes such as mucostasis and organizing pneumonia and absence of significant lymphoid infiltrate in the adjacent lung parenchyma [31].

Symptoms and Signs

Presenting symptoms include cough, dyspnea, fever, recurrent pneumonia, weight loss, and fatigue [32]. Since follicular bronchiolitis is commonly associated with underlying systemic diseases such as immunodeficiencies and connective tissue diseases, particularly rheumatoid arthritis and Sjögren’s syndrome, clinical manifestations of underlying disease can be found.

CT Findings

The main TSCT findings of follicular bronchiolitis include bilateral centrilobular small nodules and peribronchiolar nodules [11] (Fig. 18.7). Most nodules measure less than 3 mm in diameter but occasionally are as large as 1–2 cm in diameter. Other findings include patchy GGO areas, bronchial wall thickening, and patchy areas of low attenuation.

CT–Pathology Comparisons

Centrilobular small nodules and peribronchiolar nodules on TSCT reflect peribronchiolar inflammation and coalescent germinal centers [11].

Patient Prognosis

The management of follicular bronchiolitis is principally directed at the underlying disease. Corticosteroids and azathioprine therapy have been used with some success in those with progressive follicular bronchiolitis. Prognosis is generally favorable but depends on the underlying condition and the age at the time of biopsy [32].