A 49-year-old woman with no significant medical history other than a 1-month history of arthralgia of the ankle, wrist, and finger joints presented with dyspnea, which she had been experiencing for 3 days. A physical examination revealed erythema nodosum below the knees, while chest radiography and computed tomography imaging revealed bilateral hilar and mediastinal lymphadenopathy. Although this patient was initially diagnosed as having Löfgren's syndrome, only a few cases of Löfgren's syndrome with dyspnea have been reported. Therefore a video-assisted thoracic lung biopsy was performed to exclude the possibility of other diseases such as tuberculosis and malignant lymphoma. Biopsy specimens of the lung and lymph node revealed noncaseous epithelioid cell granulomas, confirming the diagnosis of sarcoidosis. The patient's dyspnea improved within 2 weeks without initiation of steroid therapy, and her arthralgia and erythema nodosum improved within 3 and 7 months from the onset of symptoms. Many authors mention that no routine biopsy is needed in a typical case of Löfgren's syndrome, but it is difficult to decide whether a biopsy should be performed in cases that present with rare symptoms, such as the present case.