High-resolution CT (HRCT) is an important diagnostic tool in detecting parenchymal and mediastinal abnormalities not typically seen on the plain chest radiograph. Accurate diagnosis relies on knowledge of the abnormal distributions in the lung parenchyma and requires pattern-based approach. Atypical patterns pose a challenge in the recognition of the disease warranting an increased awareness. We present an atypical case of sarcoidosis with ‘tree-in-bud’ pulmonary infiltrates and discuss differential diagnoses.
48-year-old male with a history of hypothyroidism and remote exposure to aerosolized chemicals and burn pits who is a lifetime nonsmoker presented with dry cough of a few months duration. Chest X-ray was obtained and revealed prominent lesion in the right lung. HRCT subsequently demonstrated multiple clusters of ‘tree-in-bud’ nodular opacities in the right upper and lower and left lower lobes. Fiber bronchoscopy showed signs of chronic bronchitis and bronchoalveolar lavage (BAL) revealed normal cell counts, with 14% neutrophils, 85% macrophages, and 1% lymphocytes. Infections with Mycobacterium tuberculosis, nontuberculous mycobacteria, Legionella pneumophilia, Mycoplasma pneumoniae, cytomegalovirus, Aspergillus species, Pneumocystis jirovecii, Histoplasma capsulatum, Blastomyces species and Cryptococcus were excluded. Bacterial cultures remained negative. Due to persistent symptoms and progressively worsening nodules on imaging, a repeat bronchoscopy with transbronchial biopsy was performed. Findings were largely nondiagnostic, showing lymphoplasmacytic infiltrates with no evidence of malignancy or granulomatous disease. Pulmonary function test was normal. Ultimately, video-assisted thoracoscopic surgery (VATS) directed lung biopsy was performed which confirmed sarcoidosis. The patient was managed conservatively. On follow-up HRCT one year later, complete resolution of lung disease was noted and patient had no clinical symptoms.
‘Tree-in-bud’ pattern on HRCT represents dilated bronchioles due to their filling by mucus, pus or fluid. This morphologic pattern can be seen in a wide variety of diseases, most commonly in infections with Mycobacterium tuberculosis, nontuberculous mycobacteria, and other bacterial, fungal, or viral pathogens. Connective tissue disorders like sarcoidosis typically show small nodules in perilymphatic distribution but in some cases nodules associated with centrilobular arteries may mimic the appearance of the ‘tree-in-bud’ pattern. Other causes include immunological, congenital and idiopathic disorders as well as aspiration or inhalation of toxic agents and in rare cases, malignancy. Awareness of alternate diagnoses for ‘tree-in-bud’ pattern is key to help guide further investigation such as bronchi alveolar lavage, transbronchial lung biopsy and VATS for timely diagnosis and appropriate management as demonstrated in our case.
Full conference title:
- ATS 2018