Resorption of intracutaneously injected Congo red.

Since the introduction of the intravenous Congo red test by Bennhold (1923), a number of writers have recorded observations on the intracutaneous injection of Congo red dye. Philpott and Freshman (1936) and Nomland (1936) observed intense and prolonged staining of cutaneous amyloid deposits in patients following the local injection of Congo red solution. Laine, Holopainen, and Makinen (1956) noted that Congo red solution injected into the apparently healthy skin of a group of rheumatoid arthritics disappeared more slowly than in control subjects. Shannon, Fessel, and Bywaters (1957) confirmed Laine's findings in a group of juvenile arthritics and observed that the delay in fading was most marked in the younger age groups. They noted that another dye, Evans' blue, failed to show this difference in fading. No cause is known for this apparent dermal avidity for Congo red in patients with rheumatoid arthritis, but Shannon and others suggest a relationship to the increased tissue retention of intravenously injected Congo red demonstrated in these subjects by Dixon, Ramcharan, and Ropes (1955). If this were so, then the skin of rheumatoid patients with secondary amyloidosis might be expected to show this delay in fading rate, perhaps to a more marked degree. The purpose of this paper is to report a study of the fading rate of intracutaneously injected Congo red in a group of mainly adult patients with rheumatoid arthritis and to compare these with a small group of patients with amyloidosis. The results are compared with those in a control group.