Intra-cutaneous Congo red in rheumatoid arthritis.

It has been claimed that, in patients with amyloidosis, the presence of amyloid material in the skin may be demonstrated by the intracutaneous injection of Congo red (Philpott and Freshman, 1936; Nomland, 1936). In the presence of amyloidosis, the area of staining is said to be more intense and to persist for a longer time than in normal skin. Recently this technique has been employed by Laine, Holopainen, and Makinen (1956) in a series of patients with rheumatoid arthritis. The fixation of the dye in the skin was measured by the time taken for the stained area to fade to a standard intensity and this was found to be significantly longer in 55 patients with rheumatoid arthritis than in thirty normal control subjects. From these results, Laine and his co-workers concluded that this phenomenon might be due to the presence of amyloid in the skin of patients with rheumatoid arthritis. This seemed quite possible since, with the decline of tuberculosis, rheumatoid arthritis is one of the chief causes of secondary amyloid. At the Postgraduate School of Medicine, London, amyloid was found in eight out of 48 autopsied cases (Missen and Taylor, 1956). Using a modified method of assessment, we have confirmed Laine's results, but our experience leads us to differ somewhat from Laine and his colleagues in their tentative conclusions cited above.