Incidence and Natural History of Idiopathic Chronic Inflammatory Demyelinating Polyneuropathy: A Population-Based Study in Iceland.

BACKGROUND AND AIM: We report a population-based study conducted in Iceland to determine the incidence, clinical characteristics and prognosis of idiopathic chronic inflammatory demyelinating polyneuropathy (CIDP) during a 21-year period.

METHODS: Cases were identified from the records of all practicing neurologists in the country, the only neurology department in the country and both neurophysiology laboratories. All index cases met the 2010 European Federation of Neurological Societies/Peripheral Nerve Society criteria for CIDP.

RESULTS: Nineteen individuals fulfilled the diagnostic criteria during the study period. The average annual incidence was 0.3/100,000 (95% CI 0.04-2.47). There were 14 men (74%) in a gender ratio of 1:2.8. The mean age at diagnosis was 57 (range 19-81 years): women, 36 years and men, 63 years; p = 0.0006. The disease course was remitting-relapsing in 21% and chronic progressive or monophasic in 79%. The average length of follow-up was 6.9 years. The standardized mortality ratio for the 21-year study period was 0.9 (95% CI 0.3-2.2).

CONCLUSION: We believe we have identified all diagnosed with CIDP in Iceland during a 21-year period. Many had no or only limited disease progression over the years and mortality is not increased compared with the general population.