A great variety of skin manifestations and the frequent occurrence of cold sensitivity, vascular symptoms with peripheral painful ulcerations, headache of migraine type, and muscle and joint symptoms are described in a series of 12 patients with an overlap syndrome compatible with mixed connective tissue disease (MCTD). The patients have been followed up for an average of 7 years. The peripheral symptoms on the extremities in particular were exacerbated by exposure to cold and caused much inconvenience and early disability for the patients. In addition to the symptoms generally connected with MCTD, some of the patients presented signs of other diseases of autoimmune type as well. For instance 2 of the patients presented autoimmune thyroiditis and one patient developed myasthenia gravis and cold agglutinin syndrome.

A total of fifty-five biopsies from fifty-two intradermal DNA skin tests were studied. The biopsies were taken, 6, 8-10, 24 or 48 h after the injection of the DNA material. Necrosis of the vessel wall was taken to be the main characteristic of a specific reaction. In forty of the fifty-two tests the results of the histological evaluation closely matched the clinical results. In five of the fifteen cases with discrepancies, the histological evaluation ruled out clinically false positive test results. In three cases of SLE on corticosteroid treatment, the histological examination gave a positive result despite a clinically negative result. In seven of the fifteen cases the discrepancies occurred in borderline cases with reactions of 5 to 6 mm diameter. The amount of inflammatory cells in positive as well as in negative reactions was also recorded. The number of polymorphonuclear cells in positive reactions increased with the age of the reaction. The number of lymphocytes was not found to increase in the positive reactions, thus differing from the delayed hypersensitivity type of reactions. Rather, the reaction was characterized by an Arthus type of hypersensitivity. On the basis of the present study it may be concluded that clinically positive tests at 6 or 8 h may merely be expressions of nonspecific vascular alterations. On the other hand, in late reactions, even in patients on systemic treatment, histological examination revealed clinically negative results to be positive. By using the histological picture of hypersensitivity angiitis as the main diagnostic criterion the specificity of the clinical reactions may be established.

A clinical evaluation of the intradermal DNA-test was carried out on a series of patients with untreated or with treated definite systemic lupus erythematosus (SLE), or with suspected SLE with or without circulating antinuclear factors. A saline solution of a commercially available DNA-preparation was used. The course of the DNA reaction was followed for 24-48 h after the injection. All nine cases of untreated definite SLE had a positive DNA test 6 h after the injection, and eight cases a positive result at 24 h. All seven patients with definite SLE who were on low-dosage systemic steroid treatment had a clinically positive. DNA test at 6 h. In all except one of these cases the test was still positive at 24 h. All five patients with definite SLE on antimalarial treatment had a positive test at 6 h which had become negative at 24 h after the injection. Eleven of the twelve patients with suspected SLE and circulating antinuclear factors had a positive DNA test at 6 h, which in nine cases persisted for 24 h. On the other hand, of the eleven ANF negative patients with various connective tissue diseases five had a positive test at 6 h. In only one of these cases it persisted for 24 h. Two of the eighteen control patients with various dermatoses exhibited a positive test at 6 h, and in one of these the positive reaction persisted for 24 h. It is concluded that the intradermal skin test using native DNA is a useful diagnostic tool for the detection of SLE when the reaction is followed up for 24 h. Antimalarial treatment seems to decrease skin reactivity to native DNA.

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