Objective: To determine the frequency of autoantibodies directed against the nucleolar organizer antigen NOR-90 [human upstream binding factor (hUBF)] in pediatric patients with systemic rheumatic diseases. Two children with antibodies to NOR-90 are reported.
Methods: Two hundred thirty-eight sera from children with systemic rheumatic diseases were screened for autoantibodies directed against hUBF by indirect immunofluorescence and immunoblotting using MOLT-4 cell extracts. Reactivity with hUBF was confirmed by immunoprecipitation of the recombinant hUBF protein.
Results: Two sera out of 238 (< 1.0%) with reactivity against hUBF were identified. One patient had recurrent abdominal pain, headache, and Raynaud's phenomenon. There has been no evidence of an active systemic rheumatic disease in more than 8 years of followup. The 2nd patient had Raynaud's phenomenon and systemic lupus erythematosus.
Conclusion: Antibodies to hUBF are rare in children with systemic rheumatic diseases. Raynaud's phenomenon was a clinical feature common to both patients.