A 48-year-old woman presented with intermittent cough and expectoration, which she had been experiencing since May 2018. In early October 2018, the aforementioned symptoms significantly progressed with dyspnea on exertion. A chest radiograph recorded at a local clinic showed increased and disordered lung markings and scattered small patchy shadows in bilateral lungs. She was diagnosed with bronchopneumonia and was administered antibiotics; however, there was no improvement in dyspnea. On 8 October 2018, her chest radiograph of regular occupational medical check-ups at the local occupational disease hospital showed diffuse punctate and nodular shadows in the bilateral lungs (Figure 1B), while the initial chest radiograph taken on June 2016 (before work) was normal (Figure 1A). Chest CT scans revealed diffuse ill-defined centrilobular nodules, as well as patchy ground-glass opacities (GGOs) in bilateral lungs, and no pleural effusion was present (Figures 2A, B). The patient quit work and was admitted to a local occupational hospital for further evaluation.
On admission, arterial oxygen tension (PaO2) was 88 mmHg at rest in room air. Her routine hematological and biochemical blood tests were normal. Autoantibodies such as an antinuclear antibody, rheumatoid factor, anti-single stranded DNA antibody, anti-double stranded DNA antibody, anti-extractable nuclear antigen antibodies, and anti-neutrophil cytoplasmic antibodies were negative. At initial presentation, pulmonary function revealed a mild obstructive pattern, with forced vital capacity (FVC) of 3.02 L (101% predicted), total lung capacity (TLC) of 5.24 L (110% predicted), forced expiratory volume in 1 s (FEV1) of 2.28 L (89% predicted), FEV1/FVC ratio of 0.75, and a reduction of diffusing capacity of carbon monoxide (DLco) of 66% predicted (Figure 2). The histological findings of transbronchial lung biopsy (TBLB) revealed sarcoid-like granulomas with multinucleated giant cells, while birefringent particles were observed in the granulomas under a polarizing microscope.