Importance of low serum DNase I activity and polyspecific anti-neutrophil cytoplasmic antibodies in propylthiouracil-induced lupus-like syndrome.

Objective: To study the role of deoxyribonuclease (DNase) I activity and ANCA in propylthiouracil (PTU)-induced lupus-like syndrome (LLS).

Methods: We compared 36 SLE patients with 17 PTU-induced LLS patients diagnosed from 2008 to 2014. We studied ANCA profile (MPO, PR3, lactoferrin, CTG, elastase, bactericidal/permeability-increasing protein), anti-dsDNA, anti-ENA, anti-nucleosome, anti-histone, anti-C1q, anti-aCL, complement components, cryoglobulins and serum DNase I activity. Healthy persons and patients without LLS treated with PTU comprised the control groups. Twelve LLS patients were serologically and clinically followed for 4.1 (S.D. 2.0) years.

Results: PTU-induced LLS patients less frequently had arthritis, renal and neurological manifestations, but more frequently had fever, purpura, urticarial-like vasculitis and ulceration (P < 0.01). PTU-induced LLS patients more frequently had polyspecific ANCA (anti-MPO, anti-elastase and anti-PR3 were most commonly detected) (P < 0.01). SLE patients more frequently had anti-dsDNA, anti-ENA, anti-nucleosome, anti-C1q (P < 0.01) and anti-histone antibodies (P < 0.05). PTU-induced LLS patients had lower DNase I activity than SLE patients and controls (P < 0.01). Discontinuation of PTU increased DNase I activity, although it did not reach the levels of controls (P < 0.01). After remission, MPO-ANCA decreased (P < 0.01), but persisted for a long time.

Conclusion: PTU, as a trigger, and low DNase I activity, as a predisposing factor, may lead to LLS. Polyspecific ANCAs are useful markers for differentiating SLE from PTU-induced LLS. Low DNase I activity might be an important prognostic biomarker for PTU-induced LLS. Monitoring of ANCA and DNase I activity may prevent long-lasting exposure to causal drugs, unnecessary immunosuppressive therapy and severe complications of LLS.