The patient, a 56-year-old woman, presented with symptoms of a lower respiratory infection, severe hypoxemia, and diffuse pulmonary infiltrates seen on a chest roentgenogram. She was a lifelong smoker whose medical history was relevant for hypertension, depression, and type II diabetes mellitus. The initial diagnosis was severe community-acquired pneumonia with ARDS. She was treated with a bilevel, positive-airway-pressure mask, antibiotics, and supportive care, and responded well to therapy. A 2-year-old chest roentgenogram obtained from another hospital revealed a similar diffuse lung process. A CT scan of the chest revealed diffuse ground-glass densities. A diagnosis of desquamative interstitial pneumonia (DIP) was suspected and was confirmed by a thoracoscopic open lung biopsy (Fig 1)
. There was no evidence of organizing pneumonia, eosinophilia, or granulomatous inflammation. The findings of all cultures of lung tissue, including those for acid-fast bacilli and fungus, were negative. Pulmonary function testing revealed restrictive disease of moderate severity (lung volumes were decreased to 62% predicted; single-breath diffusing capacity of the lung for carbon monoxide was 40%). The arterial oxygen saturation was 91% at rest while breathing room air, and 81% after walking 100 feet at a slow pace. Despite smoking cessation and treatment with prednisone, 1 mg/kg/d, the disease progressed over the next several months, with worsening restrictive disease seen on lung function test results, worsening dyspnea and hypoxemia, and the progression of infiltrates seen on chest roentgenograms (Fig 2
, top, A). The patient’s oxygen saturation while breathing room air was then 83%. In addition, she became increasingly intolerant to steroid therapy, with worsening of her diabetes. Extensive lower extremity edema and poorly healing, infected leg ulcers developed. Because our patient had not responded to treatment with corticosteroids and significant steroid morbidity was developing, the prednisone dosage was decreased to 20 mg/d. Before the institution of treatment with alternative immunosuppressant agents, she was treated with clarithromycin, 500 mg po/bid, based on the reported efficacy of macrolide antibiotics in other inflammatory lung disorders. The patient returned for follow-up after 2 weeks of antibiotic treatment, and reported a dramatic improvement in exercise tolerance and the disappearance of her previously refractory cough. Her arterial oxygen saturation was then 97% while breathing room air, falling to 91% with exercise, and a repeat chest roentgenogram obtained after 28 days of treatment showed partial clearing of the lung infiltrates (Fig 2, bottom, B). Pulmonary function testing showed improvement in vital capacity and diffusing capacity of the lung carbon monoxide, though significant restrictive disease persisted. To date, our patient has remained in remission for 3 months while receiving continued macrolide therapy, although attempts at decreasing the prednisone dosage to < 20 mg/d have been unsuccessful.