Chronic acquired demyelinating symmetric polyneuropathy classified by pattern of weakness

Objectives: To study a representative group of patients with chronic acquired symmetric demyelinating polyneuropathies, and to evaluate classification by pattern of weakness and by presence of immunoglobulin monoclonal protein (M protein). Methods: In Vest-Agder County, Norway, an unselected population of patients with chronic symmetric polyneuropathies who fulfill electrodiagnostic criteria for demyelination are registered in a database and followed up prospectively. Data were taken from the database on April 2, 2001. Patients with proximal as well as distal weakness were classified as having chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and patients with only distal symptoms as having distal acquired demyelinating symmetric polyneuropathy (DADS). Results: A total of 29 patients had chronic acquired symmetric demyelinating polyneuropathy; 15 had CIDP and 14 had DADS. The 2 categories differed regarding spinal protein level (mean +/- SD, 0.102 +/- 0.060 g/dL in CIDP vs 0.065 +/- 0.029 g/dL in DADS; P = .05); clinical course (remitting in 6 of 13 patients with CIDP vs 0 of 14 with DADS; P = .02); disability score at diagnosis (mean +/- SD, 3.3 +/- 1.0 in CIDP vs 1.9 +/- 0.6 in DADS; P < .001) and at peak of symptoms (mean +/- SD, 3.6 +/- 1.1 in CIDP vs 2.3 +/- 0.6 in DADS; P < .001); and response to immunosuppressive treatment (11 of 12 patients with CIDP vs 2 of 7 with DADS; P = .01). An M protein was detected in 8 patients (3 with CIDP and 5 with DADS). Patients with polyneuropathy with and without M protein were similar in clinical features, course, disability, and treatment response. Conclusion: Classification by presence or absence of proximal weakness separates patients with chronic acquired symmetric demyelinating polyneuropathy into groups that are different in clinical course, disability, and treatment response.