Progressive multifocal leukoencephalopathy developed in a patient with rheumatoid arthritis after treatment with an immunosuppressive agent (chlorambucil). We fell that this case lends further support to the concept that an altered immunologic state is important in the appearance of this infection, which is probably viral in origin.

In independent studies, 51% and 36% of patients with rheumatoid arthritis have been shown to possess HLA-Dw4 compared to 7% and 13% of controls. In one study Dw4 positive patients more frequently had rheumatoid factor in their sera than did Dw4 negative patients. In order to determine if the Dw4 specificity is associated with the disease or with the presence of rheumatoid factor, the frequency of this HLA antigen has been determined in 24 healthy women known to have rheumatoid factor (median titer 1 :160). Only 3 were found to have the Dw4 specificity, suggesting that this specificity is not associated with rheumatoid factor in the absence of rheumatoid arthritis. The number of documented associations between HLA and disease has risen steadily over the past several years. One of the most intriguing of these associations for rheumatologists is the association between rheumatoid arthritis and HLA-Dw4. As initially described by Stastny (1) and confirmed by McMichael et al. (2), either 5 1% or 36% of patients with rheumatoid arthritis possessed the Dw4 specificity, compared to 7% or 13% of controls, respectively. The explanation for this association is unknown, as is the explanation for every other HLA and disease association. Nonetheless, because it is anticipated that immune response genes will be found in the HLA-D region (3) and because such genes have been shown to quantitatively control antibody responses to specific proteins in several species (4). the possibility that such genes or their products play a pathogenetic role in rheumatoid arthritis must be considered.I n this regard, when rheumatoid arthritis patients who were Dw4 positive were compared with those who were Dw4 negative, a higher percentage of patients with Dw4 had rheumatoid factor (2). This correlation between rheumatoid factor positivity and the presence of HLA-Dw4, although tentative, suggests a possible explanation for the association between rheumatoid arthritis and HLA-Dw4: the presence of an immune response gene, in linkage disequilibrium with HLA-Dw4, could code for an antibody response to immunoglobulin. By definition, such a gene would be found more frequently in persons with HLA-Dw4 than in a control population.

Service of the Margaret Hague Maternity Hospital with pronounced swelling, tenderness, and warmth of the left knee and right ankle joints. The infant was the product of a full-term spontaneous delivery. The mother was noted to have a thick, yellow, vaginal discharge at the time of parturition. Because of this finding, the Cred\l=e'\procedure was done with special care. Culture of the vaginal discharge of the mother yielded N. gonococcus and penicillin therapy was promptly instituted. Mother and child were discharged from the hospital on the fifth day in apparently good health. Subsequently, on the eighth day, the infant developed tenderness and swelling of the left hand and wrist which resolved spontaneously, only to be followed shortly thereafter by swelling of the left knee. At this time, the infant was brought to pédiatrie clinic and admitted to the hospital with a presumptive diagnosis of gonococcal arthritis.On examination the patient was found to have a rectal temperature of 100.4°F. (38°C.) and a heart rate of 132 per minute. The conjunctivae appeared normal. No abnormalities of the oropharynx were noted. The lungs were clear and the heart was normal except for a sinus tachycardia. On joint examination, positive findings were limited to the left knee and right ankle. The left knee was swollen and warmer than the contralateral joint, and the overlying skin was taut, glistening, and slightly erythematous. The knee was held in a position of flexion at approximately 75°. Attempts at extension elicited strong protests from the infant. The periarticular tissue was soft in consistency and obviously tender. The right ankle also had findings consistent with an acute arthritis, characterized by swelling, redness, warmth, tenderness, and functional limitation.Aspiration of the left knee yielded 4 cc. of a thick, yellow, purulent exúdate characterized by a very poor mucin clot and a white cell count of 32,000, with polymorphonuclear leukocytes predominating. Direct smear showed both intracellular and extracellular gram-negative diplococci. Joint fluid culture yielded N. gonorrhoeae, whereas cultures taken from the nares, mouth, conjunctivae, vagina, and blood were all negative for this organism. Other laboratory findings included a hemoglobin level of 16.5 gm. per 100 ml., a hematocrit of 48 per cent, and a white blood cell count of 30,350 with the following differential: