Isolated muscular sarcoidosis causing fever of unknown origin: the value of gallium-67 imaging. An unusual case of a patient with a long-standing fever of unknown origin (FUO) is presented whose gallium-67 (67Ga) images revealed increased activity only in the calf muscles bilaterally. Other imaging modalities also failed to show chest or other abnormal findings. Subsequent biopsy of the right gastrocnemius muscle revealed noncaseating granulomas consistent with the diagnosis of sarcoidosis. When using 67Ga to evaluate a patient with a FUO, imaging of the extremities should always be included. Also, when abnormal Ga-67 uptake is present in the extremities, sarcoidosis should be included in the differential diagnosis. 