Role of antiribosomal P protein antibodies in the diagnosis of lupus isolated to the central nervous system

Background: When lupus presents with isolated central nervous system findings, the usual serologic markers are often absent and diagnostic difficulty with a delay in treatment is common. Objective: To report the usefulness of antiribosomal P protein antibodies in the diagnosis of lupus isolated to the central nervous system when results of tests for anti-double-stranded DNA antibodies are negative. Design: Case report. Setting: University medical center. Patient: The patient was evaluated and treated on referral and followed up for 1 year. Result: We describe a patient with acute onset of psychosis followed by coma and focal clonic movements with undetectable DNA antibodies. Serum antiribosomal P protein antibody levels were elevated. Steroid therapy was followed by marked clinical improvement and a decrease in antibody titer. Conclusion: Antiribosomal P protein antibodies provide an important confirmatory test for the diagnosis of lupus isolated to the central nervous system when results of tests for anti-double-stranded DNA antibodies are negative.