Löfgren Syndrome on 18F-FDG PET/CT: An Acute Manifestation of Sarcoidosis.

A 58-year-old man presented with fever, erythema nodosum, and arthralgia of knee and ankle joints. Laboratory data showed signs of inflammation, and chest x-ray revealed bilateral hilar lymphadenopathy. 18F-FDG PET/CT was acquired to analyze the underlying causes and revealed FDG accumulation in thoracic lymphadenopathy and in subcutaneous lesions and periarticular uptake. This typical triad is known as Löfgren syndrome, an acute manifestation of sarcoidosis and which, as this case shows, can be visualized on 18F-FDG PET/CT. It is important to recognize this syndrome and to discriminate it from the classic presentation of sarcoidosis because of its different diagnostic and therapeutic consequences.