Multiple Lung Nodules in an Asymptomatic Patient

Abstract

Primary pulmonary amyloidosis is an uncommon condition that may involve the pulmonary parenchyma or tracheobronchial tree manifested radiographically as a single nodule or multiple lung nodules. The diagnosis is confirmed by a lung biopsy that exhibits apple green birefringence under a polarized microscope after staining with Congo red dye. The clinical and radiographic features and diagnostic aspects of primary pulmonary amyloidosis are reviewed.Key Words: primary pulmonary amyloidosis, pulmonary nodules, apple green birefringence (Clin Pulm Med 2006;13: 368 -371) T he differential diagnosis of multiple pulmonary nodules is broad. Pulmonary nodules are commonly caused by a number of neoplastic (carcinoma, lymphoma) and infectious (mycobacterial, fungal, bacterial) processes and less commonly by sarcoidosis and collagen vascular diseases (Wegener granulomatosis and rheumatoid arthritis). Primary pulmonary amyloidosis is a rare cause of pulmonary nodules and its appearance may mimic nodules of other causes. 1 CASE REPORTA 57-year-old man was referred to the pulmonary clinic after initial radiologic evaluation demonstrated the presence of multiple pulmonary nodules. He had no respiratory complaints. Four weeks earlier, he was hospitalized for cellulitis of the right leg that resolved with antibiotic treatment. At that time, a chest radiograph detected the pulmonary nodules. He had a history of diabetes mellitus, hypertension, and obstructive sleep apnea. On examination, he appeared morbidly obese with a weight of 397 lbs. He was afebrile with a blood pressure of 120/60 mm Hg, pulse of 92 beats/min, respirations of 14 breaths/min, and room air pulse oximetry of 95%. Tongue and buccal mucus membranes were normal. Palatal arches were not present. Respiratory and cardiac examinations were normal. There was no rash, clubbing of the digits, or lymphadenopathy. Lower extremities showed changes of stasis dermatitis.Complete blood count and basic chemistry tests were normal. Total serum protein and serum protein electrophoresis were normal. Pulmonary function tests showed normal mechanics with a restrictive impairment: forced vital capacity 2.07 L (48% of predicted), forced expiratory volume in 1 second/forced vital capacity (%) of 84, and total lung capacity 3.45 L (54% of predicted). Chest radiography showed nodular opacities in the left mid and right lower zones (Fig. 1A). Thoracic computed tomography revealed multiple bilateral pulmonary nodules, the largest 2.9 cm in diameter ( Fig. 1B-D). Fiberoptic bronchoscopy showed no endobronchial abnormalities and a transbronchial biopsy of a right lower lobe was obtained. Congo red stain of the lung biopsy specimen under polarized microscopy revealed apple green birefringence characteristic of amyloid (Fig. 2). Bone marrow aspiration biopsy showed normal marrow cellularity without plasmacytosis. A diagnosis of primary pulmonary nodular amyloidosis was made.