Ultrasound findings in Löfgren's syndrome: is ankle swelling caused by arthritis, tenosynovitis or periarthritis?

Arthritis of acute sarcoidosis or Löfgren's syndrome commonly affects the ankles. However, it is often difficult to determine by clinical means whether swelling of the ankles is due to frank arthritis or involvement of periarticular tissues. Therefore, sonographic examinations were performed in 24 consecutive patients with acute sarcoidosis, 16 of them with the typical triad of Löfgren's syndrome. Joint effusions could be demonstrated only by ultrasound in 6 patients. Sonographic findings consistent with tenosynovitis were found in 8 cases. In the majority of cases (20/24) the predominant abnormalities were hypoechogenic structures within the subcutis and periarticular tissues. Thus, frank arthritis is rather a rare cause of ankle swelling in Löfgren's syndrome; more often presumed joint manifestations can be attributed to subcutaneous or periarticular inflammation.