Clinicopathologic characteristics of the lungs of patients with human T cell lymphotropic virus type 1-associated myelopathy.

Lung autopsy specimens were evaluated histologically in the six patients with human T cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM). The results revealed two histologic changes. First, lymphoid infiltrates were distributed widely in peribronchiolar and perivascular regions, subpleural regions, and the alveolus. Lymphoid infiltrates were also observed in bronchial mucosal glands in relatively large bronchi, in which the acinar epithelium was sometimes degenerated. Second, chronic inflammatory changes, such as smooth muscle hypertrophy, fibrosis, or squamous cell metaplasia, were increased significantly in the membranous bronchioles of HAM patients compared with specimens from lung cancer control patients. Such histologic changes were subclinical in most cases, but one case had an abnormal chest shadow, and two cases had recurrent pneumonia. In HAM patients, high levels of HTLV-1-specific cytotoxic T lymphocytes are believed to attack the HTLV-1-bearing cells in the lung, resulting in inflammatory reactions.