Proliferating cell nuclear antigen (PCNA) is an intranuclear protein that plays a role in DNA repair and replication. Anti-PCNA antibodies are considered a rare but highly specific marker for systemic lupus erythematosus (SLE).1 Anti-PCNA antibodies are reported to occur in approximately 2–6% of patients with SLE.2 3 Given the rare occurrence, however, little is known about the clinical relevance of a positive anti-PCNA test.

To examine whether anti-PCNA antibodies are specifically associated with SLE, we retrospectively identified all patients with anti-PCNA antibodies at the University Hospitals Leuven over a 10-year period (January 1998–December 2007). Patient sera submitted for antinuclear antibody testing were tested by conventional immunofluorescence using Hep2 …