Previous epidemiological studies have indicated that the county of Värmland in western Sweden may be a high-risk zone for multiple sclerosis (MS). The objective of this study was to determine the prevalence in the area. Hospital and general practice medical files were scrutinized. The diagnostic criteria of Poser were used, with 31 December 2002 as prevalence day. The prevalence was 170.07 per 100,000 inhabitants. The average annual incidence was 6.39 to 6.46 per 100,000 (1991-1995, 1996-2000). Multiple sclerosis was 2.3 times more common among women than men. There was a variation in prevalence among the 16 municipalities, however it was not statistically significant. The rates seemed highest in the southwestern part of the county, roughly similar in location to findings some 70 years earlier. When the prevalence ratios by geographical units for the county in 1933 were applied to the current prevalence, the distribution from these estimated cases differed from homogeneity with very high significance (p < 0.00001 ). In conclusion, this study supports previous reports indicating that Värmland continues to be a high-risk zone for MS and shares in the diffusion of the disease at the county level which we had presented for the country as a whole.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01994720.

Epidemiological studies show that susceptibility to multiple sclerosis (MS) has a strong genetic component, but apart from the HLA gene complex, additional genetic factors have proven difficult to map in the general population. Thus, localized populations, where MS patients are assumed to be more closely related, may offer a better opportunity to identify shared chromosomal regions. We have performed a genome-wide scan with 834 microsatellite markers in a data set consisting of 54 MS patients and 114 healthy family members. A group of families from a small village were possible to track back to common ancestors living in the 17th century. We used single marker-and haplotype-based transmission disequilibrium test (TDT) analysis and nonparametric linkage analysis to analyze genotyping data. Regions on chromosomes 2q23-31, 6p24-21, 6q25-27, 14q24-32, 16p13-12 and 17q12-24 were found to be in transmission disequilibrium with MS. Strong transmission disequilibrium was detected in 14q24-32, where several dimarker haplotypes were in transmission disequilibrium in affected individuals. Several regions showed modest evidence for linkage, but linkage and TDT were both clearly positive only for 17q12-24. All patients and controls were also typed for HLA class II genes; however, no evidence for a gene-gene interaction was observed.

We analysed HLA haplotypes in pairs of 78 sporadic multiple sclerosis (MS) patients and 78 healthy siblings. The presence of 2 oligoclonal IgG bands, detected by immunoblotting of the cerebrospinal fluid in healthy siblings, has previously been defined as MS immunopathic trait (MSIT), based on a cut-off derived from healthy unrelated volunteers. The frequency of MSIT was 17.9% (n=14/78 siblings). The HLA-DR(15)2 allelle was present in 21.4% (n=3/14) of the siblings with MSIT, in 40.6% (n =26/64) of the siblings without MSIT, and in 59% (n =46/78) of the patients with clinically-definite (CD) MS. The distribution of zero, one or two HLA-DR(2)15 alleles was significantly skewed towards a lower allelle count in the siblings with MSIT compared with the group of unrelated siblings with MS (P=0.002), and also lower than their related siblings with MS (P=0.1). These results suggest that the MS susceptibility gene, HLA-DR(2)15 type, does not induce MSIT, and conceivably these are two separate risk factors in the development of MS. The effect of HLA-DR(2)15 and MSIT in sporadic MS appears to be synergistic.

We report a cluster of MS cases with a common ancestry indicating heredity for MS in 85% of the cases. Lysvik is a parish where Finnish immigration was pronounced in the 17th century and there has been inbreeding to a certain extent through marriage between cousins. Thus, we interpret this aggregation as possibly being genetically based, and neurogenetic studies are now being performed. However, as two of the cases were adopted environmental factors must also be considered.