Three unrelated children (one girl and two boys) have had since birth a syndrome characterized by a permanent skin rash which becomes more intense during flare-ups associated with fever, lymphadenopathy, splenomegaly, and arthritis symmetrically involving the large joints. In one boy, typical psoriasis was observed at age 3 years. In two patients, roentgenograms of the joints showed early patellar ossification and an abnormal epiphyseal appearance. The three children also had neurologic involvement, with mental retardation, enlarged head circumference, eye lesions, late closure of the anterior fontanel, and a chronic meningitis with infiltration by polymorphonuclear cells. No immunologic abnormalities were found, but polymorphonuclear cells infiltrated the skin, lymph nodes, synovial fluid, and CSF.