Skin denervation and cutaneous vasculitis in systemic lupus erythematosus

To understand the clinical significance and mechanisms of cutaneous denervation in systemic lupus erythematosus (SLE), we assessed intraepidermal nerve fibre (IENF) density of the distal leg in 45 SLE patients (4 males and 41 females, aged 38.4 +/- 13.6 years) and analysed its correlations with pathology, lupus activity, sensory thresholds and electrophysiological parameters. Compared with age- and gender-matched control subjects, SLE patients had lower IENF densities (3.08 +/- 2.17 versus 11.27 +/- 3.96 fibres/mm, P < 0.0001); IENF densities were reduced in 38 patients (82.2%). Pathologically, 11 patients (24.4%) were found to have definite cutaneous vasculitis; the severity and extent of cutaneous vasculitis were correlated with IENF densities. Patients with active lupus had even lower IENF densities than those with quiescent lupus (1.86 +/- 1.37 versus 4.15 +/- 2.20 fibres/mm, P = 0.0002). By linear regression analysis, IENF densities were negatively correlated with the SLE disease activity index (r = 0.527, P = 0.0002) and cumulative episodes of lupus flare-up within 2 years before the skin biopsy (r = 0.616, P = 0.0014). Clinically, skin denervation was present not only in the patients with sensory neuropathy but also in the patients with neuropsychiatric syndrome involving the CNS. SLE patients had significantly elevated warm threshold temperatures (P = 0.003) and reduced cold threshold temperatures (P = 0.048); elevated warm threshold temperatures were associated with the reduced IENF densities (P = 0.032). In conclusion, cutaneous vasculitis and lupus activities underlie skin denervation with associated elevation of thermal thresholds as a major manifestation of sensory nerve injury in SLE.