Some patients with systemic lupus erythematosus have selective loss of small-diameter nerve fibers, while larger nerve fibers are unaffected.
To determine intraepidermal nerve fiber densities in patients with different chronic inflammatory autoimmune diseases.
Stavanger University Hospital, Stavanger, and Haukeland University Hospital, Haukeland, Norway.
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).
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.
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.
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.