Study objectives: Human T-cell lymphotropic virus type 1 (HTLV-1)-associated bronchiolitis and diffuse panbronchiolitis might overlap. We examined whether these conditions can be differentiated by comparing their clinical features and the effect of long-term macrolide treatment.
Patients and methods: Fifty-eight Japanese patients, including 15 with HTLV-1–associated bronchiolitis and 43 with diffuse panbronchiolitis. Both conditions were clinically compared using the clinical criteria for diffuse panbronchiolitis, including findings from CT scans and BAL fluid testing. Pulmonary function, blood gas levels, and cold hemagglutinin (CHA) levels were assessed before and after long-term treatment with macrolides. Interleukin-2 receptor (IL-2R) expression in T cells obtained from the BAL fluid of patients with HTLV-1–associated bronchiolitis or diffuse panbronchiolitis was analyzed by flow cytometry.
Results: Clinical, laboratory, radiologic, and bacterial features were strikingly similar in both groups, except for the fact that patients with HTLV-1–associated bronchiolitis had a higher ratio of IL-2R–positive cells in the BAL fluid. The histopathologic features were also similar. Long-term treatment with macrolides improved Pao2, FEV1, and CHA in patients with HTLV-1–associated bronchiolitis to a lesser extent than in those with diffuse panbronchiolitis, and Pao2 and FEV1 in the group of patients with HTLV-1–associated bronchiolitis who had high IL-2R levels did not respond after therapy.
Conclusions: These findings showed that the clinicopathologic features of the two conditions are quite similar, suggesting that diffuse panbronchiolitis is a chronic pulmonary manifestation of HTLV-1 infection. However, HTLV-1–associated bronchiolitis might be associated with conditions that are distinct from those of diffuse panbronchiolitis based on the different responses to macrolide treatment and the difference in the number of activated T cells bearing IL-2R in the lungs.