A 60-year-old Japanese man with a history of arteriosclerosis obliterans visited our hospital. He had a history of smoking until a month before the visit (40 pack-years) and no history of environmental exposure. About a year prior to the visit, he became aware of dyspnea on exertion, which gradually increased. Approximately six months leading up to his visit, Raynaud's phenomenon appeared in his left index finger from time to time. His family doctor observed an abnormal shadow on the patient's chest radiographs and referred him to our hospital for further examination.
On the patient's first visit to our hospital, his vital signs were as follows: heart rate, 72 bpm; blood pressure, 134/93 mmHg; and body temperature, 35.9  C. His percutaneous arterial blood oxygen saturation was 96% on room air, and his respiratory rate was 14 breaths/min. Chest examination revealed fine crackles in both lower lung fields. No skin rash, joint pain and swelling, muscle weakness, or other physical findings suggestive of connective tissue disease were observed. Laboratory testing on admission revealed a white blood cell count of 6300/muL, a hemoglobin concentration of 15.0 g/dL, and a platelet count of 21.6 x 103/muL. The patient had a C-reactive protein concentration of 0.50 mg/dL and a lactate dehydrogenase concentration of 351 IU/L. His Krebs von den Lungen-6 concentration was 526 U/mL, and that of his surfactant protein-D was 166 ng/mL. Antinuclear antibodies were detected at a titer of 1:320 (with a cytoplasmic pattern), although no antibodies specific for connective tissue disease or markers of vasculitis were detected.
High-resolution computed tomography (HRCT) of the patient's chest revealed patchy, bilateral ground-glass opacities and reticular abnormalities in the upper to lower lobes. In addition, there were cystic spaces in the ground-glass opacities (Fig. 1). Pulmonary function tests demonstrated neither restrictive impairment nor airway obstruction; however, a reduced diffusing capacity of the lung for carbon monoxide (DLCO) was observed (59% of the predicted capacity). Bronchoalveolar lavage fluid from the right middle lobe (B5) revealed a total cell count of 5 x 105 cells/mL (82% macrophages, 7% lymphocytes, 6% neutrophils, and 5% eosinophils). TBLC was performed on S8a and S8b of the right lung. The biopsy specimens were 5.5 x 2.5 mm (S8a) and 4.4 x 3.0 mm (S8b) in size. Histologically, alveolar macrophages with abundant eosinophilic cytoplasm uniformly fill the air spaces. The alveolar and interlobular septa were infiltrated with inflammatory cells (Fig. 2). The fibrosis was mild, and the alveolar architecture was relatively well maintained. The lesion was compatible with a histological diagnosis of DIP.
Despite three continuous months of cessation of smoking, the patient's dyspnea on exertion worsened, and his DLCO deteriorated to 45% of the predicted capacity. Subsequently, we started immunosuppressive treatment with prednisolone (30 mg/day; 0.5 mg/kg/day), with gradual tapering of the dose, which led to an improvement in pulmonary symptoms. Moreover, HRCT performed 3 months later confirmed this improvement, and the patient's DLCO had improved to 75% of the predicted capacity, and no adverse or unexpected events had occurred.