Intraepidermal nerve fiber densities in chronic inflammatory autoimmune diseases.

BACKGROUND: Some patients with systemic lupus erythematosus have selective loss of small-diameter nerve fibers, while larger nerve fibers are unaffected.

OBJECTIVE: To determine intraepidermal nerve fiber densities in patients with different chronic inflammatory autoimmune diseases.

DESIGN: Cross-sectional study.

SETTING: Stavanger University Hospital, Stavanger, and Haukeland University Hospital, Haukeland, Norway.

PATIENTS: Sixty patients with systemic lupus erythematosus (SLE) (mean +/- SD age, 43.2 +/- 13.5 years), 61 patients with primary Sjögren syndrome (age, 57.1 +/- 14.7 years), and 52 patients with rheumatoid arthritis (age, 57.4 +/- 12.3 years) were compared with 106 healthy subjects (age, 49.0 +/- 19.6 years).

INTERVENTIONS: Skin biopsy specimens.

MAIN OUTCOME MEASURES: To evaluate small-diameter nerve fiber loss, intraepidermal nerve fiber densities were measured in skin punch biopsy specimens obtained from the distal part of the leg.

RESULTS: The mean +/- SD densities were 7.5 +/- 3.8 fibers/mm in patients with SLE, 9.2 +/- 3.8 fibers/mm in primary Sjögren syndrome, and 10.9 +/- 5.4 fibers/mm in rheumatoid arthritis vs 12.4 +/- 4.6 fibers/mm in healthy subjects. Densities were significantly less in patients with SLE vs patients with rheumatoid arthritis and vs healthy subjects (P<.001 for both), as well as in patients with primary Sjögren syndrome vs healthy subjects (P<.001). Eight patients (13%) with SLE, 2 patients (3%) with primary Sjögren syndrome, and 2 patients (4%) with rheumatoid arthritis had densities below the lower reference limit of 3.4 fibers/mm, consistent with small-diameter nerve fiber neuropathy.

CONCLUSION: The degree of loss of small-diameter nerve fibers differs among patients with these chronic inflammatory autoimmune diseases, likely reflecting differences in pathogenesis and organ affinity of the individual disease entities.