Summary:Bone marrow transplantation (BMT) recipients, particularly those with chronic graft-versus-host disease (GVHD), suffer from respiratory tract problems, including bronchiolitis obliterans (BO) and recurrent lower respiratory tract infections. Minute cilia beat continuously on the surface of respiratory mucosa, and this beating maintains the sterility of the lower respiratory tract. Dysfunction of respiratory cilia could lead to development of recurrent respiratory tract infections, which are also features of BMT recipients, although ciliary function has not been systematically studied among these subjects. We have, therefore, investigated the ciliary beat frequency (CBF) of 36 Chinese patients who had undergone allogeneic BMT. The CBF was significantly lower in the BMT group compared to controls (P Ͻ 0.001). The reduction in CBF was more severe in patients with cGVHD and BO compared with their counterparts (P = 0.048 and P = 0.077, respectively). There was a correlation between CBF with forced expiratory flow rate FEF (P = 0.024) and forced expiratory volume FEV (P = 0.044). We conclude that abnormal ciliary clearance is a common feature after allogeneic BMT, particularly among patients with BO and cGVHD. Further studies are indicated to evaluate this important phenomenon, which could be an important cause of the susceptibility for BMT recipients to respiratory infections. Bone Marrow Transplantation (2001) 27, 1147-1151. Keywords: bone marrow transplantation; ciliary function; bronchiolitis obliterans; graft-versus-host disease Survivors of bone marrow transplantation (BMT) often suffer from respiratory complications. These include conditioning toxicity, infective complications and bronchiliotis obliterans (BO). 1 BO is characterized histologically by obliteration and destruction of lumen of respiratory bronchioles by granulation tissue, mononuclear cell infiltration, and fibrosis. Clinically, it manifests itself as an irreversible obstructive defect affecting small airways, usually in the absence of proven infection. The exact mechanism for the cause of such abnormalities after BMT is unknown, but there is a documented association with chronic graftversus-host disease (cGVHD), total body irradiation, and prior chemotherapy exposure. 2,3 Cilia are minute hair-like structures present on the surface of respiratory mucosa. Each of these cilia beat continuously at 10-18 Hz, and this beating creates a constant flow of periciliary fluid, which is responsible for maintaining the sterility of the lower respiratory tract. Ciliary structure and function are highly conserved among all species and at different levels of the respiratory tract. 4 Dysfunction of respiratory cilia leads to development of recurrent upper and lower respiratory tract infections, bronchiectasis and small airway obstruction. This is exemplified by Kartagener's syndrome (sinusitis, bronchiectasis and dextrocardia) which is the most obvious clinical expression of a spectrum of diseases caused by abnormal ciliary function. 5 Defects in ciliary ...