INTRODUCTION: Fibrosing mediastinitis (FM) is a condition of excessive fibrous tissue deposition leading to compression or constriction of mediastinal structures, most commonly stemming from mycobacterial or fungal infections. Tracheobronchial amyloidosis (TBA) is an extremely rare condition associated with the interposition of amyloid protein in the walls of the tracheobronchial tree. The following is a case of endobronchial amyloidosis in a patient with prior history of FM, leading to concentric airway narrowing.
CASE PRESENTATION: A 34yo woman presented with progressive dyspnea, wheezing and blood streaked sputum over 1 year. Past medical history was significant for asthma. Twelve years ago, she had a biopsy of a mediastinal mass incidentally found on chest radiograph. The biopsy was consistent with FM, thought most likely from histoplasmosis. Initially, no treatment was instituted, and the patient remained in normal heath until three years ago when symptoms of airway obstruction worsened, leading to prolonged treatment with oral corticosteroids and bronchodilators. Although initial pulmonary function testing was significant only for airflow limitation (FEV1 65% predicted), recent testing showed combined obstruction and restriction with preservation of gas transfer (DLCO 101.4% of predicted). CT imaging demonstrated a large conglomeration of lymph nodes with calcifications which encased and narrowed the right main-stem bronchus, and the right middle lobe bronchus was nearly occluded. Fiberoptic bronchoscopy was undertaken with the consideration of airway stenting. Under direct visualization, the right mainstem bronchus was concentrically narrowed with hyperemic, friable mucosa. An endobronchial biopsy from the proximal right side of the main carina showed submucosal deposition of an eosinophilic, acellular material and Congo-Red stain was focally positive. Amyloid A stain was positive, consistent with a diagnosis of TBA. Retrospective analysis of the specimens obtained 12 years prior including Congo-Red staining was void of amyloid protein. A diagnosis of FM with secondary TBA was made.
DISCUSSIONS: Both FM and TBA are quite rare. In the literature, we were unable to find an association between the two entities. Scant qualitative descriptions of the airway mucosa in FM have been made. Manali (2003) reviewed 3 cases FM with airway descriptions analogous to ours. Moreover, patients with TBA have presenting symptoms consistent with our patient (Berk 2002) and similar bronchoscopic airway descriptions. The relationship between TBA and FM in our patient is unclear. An initial insult, possibly histoplasmosis, led to the development of FM. Potentially, slow progression of fibrotic airway invasion with concomitant inflammation may have led to deposition of amyloid A protein. Functionally, the two processes in concert led to a profound narrowing of the airways with mucosal disruption manifested by symptoms of airflow limitation and bleeding. Treatment options for both FM and TBA are quite limited. Steroids have been tried with variable results. For central airway constriction, airway stenting with endobronchial debridement or laser resection is possible, although the diffuse nature of the infiltrative process may limit its utility. Nevertheless, the prognosis for both disorders remains dismal. Recently, several case reports of external beam radiation as a treatment modality for TBA have been published with promising early outcomes.
CONCLUSION: We believe this case is a unique description of the mucosa in a patient with FM. Furthermore, the presence of amyloid protein from biopsies has not been described. As there is heterogeneity in patient responses to FM, with only a subset of patients developing symptoms of hemoptysis along with airflow limitation, it begs the question of whether secondary amyloidosis is an under recognized epiphenomenon in patients with airway infiltration of fibrous material.
DISCLOSURE: Jeffrey Hoag, None.