Background Proliferating cell nuclear antigen (PCNA) antibodies are a rare type of antinuclear antibodies (ANA), historically considered highly specific for systemic lupus erythematosus (SLE). Recent studies showed they can be present in other autoimmune diseases, viral infections or tumors. Our aim was to clinically describe patients positive for anti-PCNA antibodies.
Methods We retrospectively identified patients with a PCNA pattern by indirect immunofluorescence (IIF), subsequently confirmed by immunoblot, selected among patients tested for ANA, between January 2006 and August 2019. Clinical and analytical data were obtained from medical records.
Results 11014 samples (excluding follow-up tests) were tested for ANA, 2642 (23.99%) were positive (titer >1/160), 26 (0.98%) had a PCNA pattern by IIF but only 6 (0.23%) were anti-PCNA positive. Mean patients’ age was 51.5±17.93 years-old and the majority were female (83%). Half had SLE (including one Overlap Syndrome). Other autoimmune diseases included Antiphospholipid syndrome [n=2, 33%], Systemic Sclerosis [n=1, 17%] and Behçet Disease [n=1, 17%]. One patient developed metastasis from an occult neoplasia and none had viral disease. Almost all patients had cutaneous manifestations [n=5, 83%]. Half had articular [n=3, 50%] and neurological manifestations [n=3, 50%]. Median ESR and RCP were slightly elevated. None had complement consumption. Mean GFR was normal, with one patient showing low level of proteinuria. Anti-dsDNA, anti-SSA, anti-M2 and anti-cardiolipin were also found in the sera. Two patients were under hydroxychloroquine [n=2, 33%] and one under prednisolone 10 mg [n=1, 17%] (table 1).
Conclusions Our study confirmed that anti-PCNA antibodies can be present in other autoimmune diseases and are not SLE specific. Given its rare prevalence, evidence about the clinical relevance of anti-PCNA antibodies is lacking. Larger studies are needed to further evaluate its role.
Skin: Malar rash and/or photosensitivity and/or oral/genital ulcers and/or Raynaud phenomenon and/or telangiectasias and/or microstomy and/or digital ulcers and/or skin sclerosis;
Joints: Arthralgias and/or arthritis;
Neurological: Focal neurological symptoms and/or dementia and/or cerebrovascular disease;
Constitutional: Fatigue and/or weight loss; Renal: serum creatinine elevation and/or proteinuria and/or hematuria; Muscle: Myalgias and/or myositis;
Sicca: Dry mouth/eyes;
RCP: Reactive C protein;
ESR: Erythrocyte sedimentation rate;
GFR: Glomerular filtration rate.
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