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Babies and Children's Hospital of New York Columbia-Presbyterian Medical Center New York, NY 10032
Calcification of tracheobronchial cartilage on chest radiographs has long been recognized as an age-related phenomenon [1]. Although CT has been shown to be more sensitive to the presence of tracheobronchial calcification than conventional radiography [2], this finding is still age-related, occurring almost exclusively in patients who are more than 40 years old. We report a case of tracheobronchial calcification on CT in an 18-year-old woman receiving long-term warfarin sodium therapy.
An 18-year-old woman with a history of congenital mitral valve regurgitation presented with increasing dyspnea and exercise intolerance. Because she had undergone mitral valve replacement at age 14 months and again at 11 years, she had received long-term warfarin sodium therapy. In addition, she had been treated for ventricular ectopy with amiodarone for the past 3 years. Recent declines in pulmonary function test results and cardiac catheterization findings of pulmonary arterial hypertension prompted a high-resolution CT examination of the chest to exclude drug-induced pulmonary interstitial fibrosis. CT failed to reveal any interstitial lung disease but clearly showed the incidental finding of tracheobronchial cartilage calcification (Fig. 3A,3B), which could easily have been missed on a chest radiograph obtained the same day.
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During the past 15 years, two articles have reported tracheobronchial cartilage calcification on chest radiographs of children who had undergone mitral valve replacement surgery. In these reports, four of five patients were known to be treated with warfarin sodium, implicating the drug as an etiologic agent [3, 4]. Subsequent work showed an increased incidence of tracheobronchial calcification in adults receiving warfarin sodium versus that in age-matched control subjects (47% versus 19%, respectively) [5].
The mechanism of warfarin sodium-induced tracheobronchial cartilage calcification remains obscure because it is also a normal age-related process. However, because warfarin embryopathy manifests as calcifications in and around joints and airway and nasal cartilages, it is possible that the mechanisms of these two entities are related. Researchers studying rats have found calcification of cartilage and elastic connective tissue in animals maintained on warfarin [6,7,8]. These findings support the hypothesis that warfarin inhibits normal formation of a vitamin K-dependent protein that prevents calcification of cartilage and connective tissue.
As more CT examinations are performed on younger patients receiving warfarin, more cases of tracheobronchial calcification will be seen. Radiologists should realize that this finding is not normal in pediatric or young adult patients and should be aware of its association with warfarin sodium therapy.
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