Deficiency of mannose‐binding lectin has been shown to be a risk factor for cystic fibrosis (CF) patients. We, therefore, decided to treat a patient with CF, mannose‐binding lectin deficiency, severe bronchopulmonary Pseudomonas aeruginosa infection, and rapid deterioration of lung function with purified mannose‐binding lectin in an attempt to ameliorate the course of the lung disease. The mannose‐binding lectin used originated from pooled human donor plasma and was given as an intravenous infusion twice a week for a period of 3 months.

The patients's clinical condition was stabilized during the treatment period, but was not improved. No adverse events were observed. However, the lung function assessed as percent forced expiratory volume in 1 sec (FEV₁%) and percent forced vital capacirt (FVC%) correlated significantly with the mannose‐binding serum lectin levels (rho = + 0.68, P = 0.008, and rho = + 0.73, P = 0.004). Additionally, an inverse correlation with the acute phase‐reactant C‐reactive protein and the proinflammatory cytokine IL‐6 was observed (rho = −0.49, P = 0.007 and rho = −0.41, P = 0.04, respectively).

The results emphasize the importance of mannose‐binding lectin as a secondary disease modifier in CF. Moreover, purified mannose‐binding lectin can safely be administered to chronically ill patients, and may be a potential treatment in CF and other diseases in which mannose‐binding lectin deficiency plays a pathophysiological role. Pediatr Pulmonol. 2002; 33:201–207. © 2002 Wiley‐Liss, Inc.