Evoked potential testing in relatives of multiple sclerosis patients

Multiple sclerosis immunopathic trait and HLA-DR(2)15 as independent risk factors in multiple sclerosis

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. Multiple Sclerosis 2007; 13: 441-445. http://msj.sagepub.com

The human magno and parvo systems and selective impairments of their functions

The magno and parvo systems, consisting of large and small cells respectively and showing the greatest differences in temporospatial characteristics, are two of the most interesting channels in the organization of retinotopic input pathways of the human visual system. We tested the hypothesis that selective lesions of fibers of a specified diameter occurring in pathology of the conducting pathways, i.e., multiple sclerosis, could be used as a "key" for studies of the different functional properties of the magno and parvo systems. Measurements were made of spatial-frequency contrast sensitivity in healthy subjects and patients in the early stages of multiple sclerosis. Decreased sensitivity at low and intermediate or at high spatial frequencies provided indirect reflections of changes in the activities of the magno and parvo systems. These psychophysical data are compared with electrophysiological results. The amplitudes of the early components of visual evoked potentials reflect activation of the two systems in healthy people and patients with multiple sclerosis. We identified two groups of patients, with statistically significantly dominant lesions of the magno and parvo systems respectively.

Clinical multiple sclerosis occurs at one end of a spectrum of CNS pathology: a modified threshold liability model leads to new ways of thinking about the cause of clinical multiple sclerosis

Multiple sclerosis (MS) is a complex trait, the causes of which are elusive. A threshold liability model influences thinking about the causes of this disorder. According to this model, a population has a normal distribution of genetic liability to MS. In addition, a threshold exists, so that MS begins when an individual's liability exceeds the MS threshold; environmental and other causative factors may increase or decrease an individual's MS liability. It is argued here, however, that this model is misleading, as it is based on the incorrect assumption that MS is a disorder that one either has or does not have. This paper hypothesizes, instead, that patients with a diagnosis of MS share identical CNS pathology, termed MS pathology, with some individuals who have a diagnosis of possible MS and with some apparently healthy individuals, who may never have a diagnosis of MS. In order to accommodate this hypothesis, the current threshold liability model is modified as follows. (1) In addition to a normal distribution of MS liability within a population, a spectrum of MS pathology occurs in some who have a high MS liability. (2) A clinical MS threshold exists at a point on this liability distribution, where the burden and distribution of MS pathology permits a diagnosis of clinical MS. (3) Additional thresholds exist that correspond to a lower MS liability and a lesser burden of MS pathology than occur at the clinical MS threshold. This modified threshold model leads to the postulate that causes act at various time points to increase MS liability and induce MS pathology. The accumulation of MS pathology sometimes leads to a diagnosis of clinical MS. One implication of this model is that the MS pathology in clinical MS and in some with possible MS differs only in the extent but not in the type of CNS injury. Thus, it may be possible to obtain insight into the causative environmental factors that increase MS liability and induce MS pathology by focusing on patients who have clinical MS; some environmental factors that induce new lesions in patients with clinical MS may be identical to those that induce MS pathology in genetically susceptible individuals who do not have clinical MS. Identification of these causative factors has importance, as specific treatment may prevent the accumulation of MS pathology that leads to the significant CNS damage associated with clinical MS.

The multiple sclerosis trait: a disease waiting to happen?

There is increasing evidence that the etiology of MS is heterogeneous. MS is often described as a "disease waiting to happen". The pathogenesis of the critical transition to clinical disease according to diagnostic criteria is largely unknown. The role of environment and chance must also be considered. Implications for counselling "at risk" individuals, based on family history, are discussed.

A whole genome screen for association in Polish multiple sclerosis patients

We have performed the first systematic search for MS susceptibility genes completed in the Polish population. This screen was performed using 6000 microsatellite markers typed in pooled DNA from cases (n=200), controls (n=200) and trio families (n=129). Five associated markers are identified, one (D6S2444) from the HLA region and four are from novel regions not previously associated with MS, 2p16 (D2S2153), 3p13 (D3S3568), 7p22 (D7S2521) and 15q26 (D15S649).

MTR discloses subtle changes in the normal-appearing tissue from relatives of patients with MS

The presence of normal-appearing brain tissue (NABT) changes was investigated in 30 first-degree relatives of patients with MS, using magnetization transfer ratio (MTR) histograms. When compared with controls, relatives of patients with familial (p = 0.01) and sporadic (p = 0.01) MS had lower NABT MTR histogram peak heights. This study suggests a reduction of truly normal NABT in asymptomatic relatives of patients with MS.

The epidemiology of multiple sclerosis

Although the cause of multiple sclerosis (MS) is unknown, epidemiologic studies support both genetic and environmental components of susceptibility. Reports of clusters, small "epidemics," geographic variation in prevalence, and alteration of MS susceptibility by migration support an environmental factor (or factors). The higher risk for MS in Europeans and in relatives of patients and the existence of MS-resistant ethnic groups support genetic predisposition. Findings from epidemiologic studies are most consistent with an environmental influence occurring on a background of genetic susceptibility as the cause of MS. Currently, there is little evidence for a single or unique environmental cause of MS.

British Isles survey of multiple sclerosis in twins: MRI

64/105 subjects who have a twin with multiple sclerosis included in a study of clinical concordance also underwent MRI of the brain. 8/23 monozygotic and 1/41 dizygotic co-twins from this subgroup were clinically concordant of whom 8/9 had MRI appearances typical of multiple sclerosis. Of the 48 clinically discordant twins aged less than 60, abnormalities on MRI were detected in 6/15 (40%) monozygotic and 13/33 (39%) dizygotic twins compared with 7/37 (19%) healthy age-matched controls. Abnormalities on MRI typical of multiple sclerosis (defined by the Fazekas criteria) were, however, present in only 2/15 (13%) monozygotic and 3/33 (9%) dizygotic twins and 0/37 controls. These results suggest that about 10% of monozygotic and dizygotic twins have "subclinical multiple sclerosis". It is likely that most of the MRI abnormalities seen in clinically discordant twins, however, represent incidental pathology.

Multiple sclerosis: occurrence of myelin basic protein peptide-reactive T cells in healthy family members

Genetic factors influence the susceptibility to multiple sclerosis (MS). This disease is accompanied by augmented T cell responses to CNS myelin components such as myelin basic protein. To evaluate the familial occurrence of such T cell autoreactivity, we have studied 12 MS families including 37 healthy first-degree relatives for occurrence of numbers of interferon-gamma (IFN-gamma) secreting cells among blood mononuclear after culture in presence of myelin basic protein (MBP), eight synthetic MBP peptides and the control antigen acetylcholine receptor (AChR). There were no differences between MS patients and healthy family members regarding frequencies of autoreactive T cells recognizing MBP, the eight different MBP peptides or AChR. None of the MBP peptides predominated as T cell antigen among the MS patients or their unaffected family members. In some families the highest number of MBP peptide reactive T cells were found among unaffected family members. No correlation was observed between numbers of MBP or MBP peptide reactive T cells in various subjects and their HLA-DR-DQ phenotypes. In conclusion, this study has revealed the presence of MBP and MBP peptide reactive T cells of similar frequencies in MS patients and their healthy family members.

A population-based study of multiple sclerosis in twins: update

This study is a 7.5-year follow-up of a population-based series of twins with multiple sclerosis (MS) whose mean age now exceeds 50 years. The twin pairs were identified through the Canadian nationwide system of MS clinics and were drawn from a population of 5,463 patients. After 7.5 years, the monozygotic concordance rate increased from 25.9 to 30.8% and the dizygotic-like sex concordance rate from 2.4 to 4.7%. These results are very similar to those of other population-based studies and to our own modified replication twin data reported here. We interpret the data to mean that MS susceptibility is genetically influenced, and a single dominant or even a single recessive gene is unlikely to account for this effect. The difference in concordance rates suggests that at least two or more genes are operative. These data also have important implications for the nature of the environmental effect(s) in MS susceptibility. Most monozygotic twins are discordant even after a correction for age and magnetic resonance imaging findings. This unambiguously demonstrates the powerful effect of nonheritable factors.

Multiple sclerosis in 54 twinships: concordance rate is independent of zygosity. French Research Group on Multiple Sclerosis

In a large population-based multiple sclerosis (MS) sample (n = 7,951), 116 twins were identified (1.4%), of which it was possible to contact 97. In 27 pairs, the twin of the patient with MS was dead. Among the 70 remaining pairs, 16 were excluded because either the index patient or their twin did not accept protocol requirements. The final sample included 54 pairs. Twin zygosity was determined by DNA fingerprint analysis. We found 17 monozygotic pairs and 37 dizygotic pairs. One of the 17 monozygotic pairs (5.9%) and 1 of the 37 dizygotic pairs (2.7%) were concordant for MS. In 42 of the clinically unaffected twins, magnetic resonance imaging (MRI) of the brain was performed, and 9 scans were classified as indicative of MS. Three of these 42 patients had abnormal visual-evoked potentials, but all 3 had normal MRI scans. The overall proportion of pairs in which the co-twin had some form of clinical, radiological, or electrophysiological abnormality was approximately 30%; this proportion was independent of zygosity.

Familial multiple sclerosis: MRI findings in clinically affected and unaffected siblings

Subclinical demyelinating lesions may occur in the brains of asymptomatic individuals, and the first-degree relatives of multiple sclerosis (MS) patients are at particular risk. Clinical and MRI examinations were performed in nine sibships from families with two or more cases of MS. These included 14 patients with clinically definite MS, three patients with clinically probable MS, and 27 asymptomatic siblings. Systematic criteria were applied to MRI interpretations to increase their specificity for MS. Thirteen (76%) of the 17 patients with MS showed lesions suggesting MS. Lesions were also found in six (38%) of the 16 asymptomatic siblings under age 50 and in eight (73%) of the 11 over age 50. Judged by stringent criteria, the lesions of only three (11%) of the 27 asymptomatic siblings were considered to be due to demyelination. The results demonstrate the occurrence of subclinical demyelination in asymptomatic siblings of MS patients and stress the importance of clinical follow up and MRI studies of the first-degree relatives when classifying them as healthy in family studies.

Magnetic resonance imaging studies in multiple sclerosis twins

Magnetic resonance (MR) imaging examinations were performed on a series of seven sets of twins (four monozygotic and three dizygotic) and one set of triplets who were clinically discordant for multiple sclerosis (MS). MR abnormalities were detected in some of the unaffected monozygotic pairs of twins.

Familial multiple sclerosis

Siblings of patients with multiple sclerosis have an increased risk of developing the disease. In this report we describe 3 families with multiple affected members, representing the largest published aggregation of cases in first degree relatives. In the 2 families in which HLA tissue-typing was performed the affected individuals shared part of the haplotype HLA-DR2 (+ HLA-DQW1), BfS (+ C2C), C4A3, C4B1. The implications of these findings for the aetiology of multiple sclerosis are discussed.