D-dimer levels as a marker of cutaneous disease activity: case reports of cutaneous polyarteritis nodosa and atypical recurrent urticaria.

IMPORTANCE Biochemical markers of disease allow clinicians to monitor disease severity, progression, and response to treatment. C-reactive protein and erythrocyte sedimentation rate are commonly used biochemical markers of inflammatory disease. We present 2 cases that indicate that D-dimer levels may be useful as a potential biochemical marker of disease activity in certain cutaneous inflammatory conditions. OBSERVATIONS We report 2 cases in which clinical disease activity correlates with D-dimer levels. The first case is a woman in her 50s with a diagnosis of cutaneous polyarteritis nodosa. The second case is a man in his 20s with recurrent urticaria. In both patients, plasma D-dimer levels increased with clinical evidence of disease activity and decreased with treatment and resolution of the disease flare. Interestingly, serum C-reactive protein levels did not correlate with disease activity and were found to be normal during clinically active disease. CONCLUSIONS AND RELEVANCE We show the potential value of D-dimer measurements as a marker of vasculocentric and/or vasculopathic inflammation and suggest that vascular endothelial damage may be ongoing in certain cutaneous inflammatory conditions.