Birbeck granules in synovial cells from a patient with rheumatoid arthritis.

Although Langerhans cells were first described as long ago as 1868, it is only relatively recently that details of their structure and function have been ascertained. They appear to be of importance in immune reactions and have been found in mammals in most squamous epithelia, including skin, buccal mucosa, esophagus, and vaginal and rectal mucosa. One of features of these cells is the presence of organelles called Birbeck granules on electron microscopy. We report the presence of cells containing Birbeck granules in the synovium of a patient with rheumatoid arthritis.