BackgroundThe relationship between prevalence of multiple sclerosis (MS) and latitude may be due to both genetic and environmental factors. The hypothesis that, in Ireland, MS prevalence is increasing and that northesouth differences relate to variation in serum 25-hydroxyvitamin D (25(OH)D) levels was tested in this study.

The contribution of human leucocyte antigen (HLA) to the genetic risk for multiple sclerosis (MS) in patients of Northern European Caucasoid ancestry has been known since the 1970s. The northern part of Ireland, including county Donegal, is known to be a high-risk area for the development of MS. Recorded prevalence rates for county Wexford in the south-east Ireland have been markedly lower and suggest the existence of a prevalence gradient within the island. To evaluate the association of HLA-DRB1 and -DQB1 haplotypes with MS in both Wexford and Donegal, we examined a total of 118 patients and 400 regionally matched controls. The aim of this exploratory study was to test the possibility of heterogeneity in HLA class II associations with MS and to identify potential predisposing or protective haplotypes, associated with MS risk in Ireland. We confirmed the association of DRB1*1501-DQB1*0602 haplotype carriage with MS in both Wexford [odds ratio (OR) = 2.95, P= 0.0020, P(cor)= 0.0220] and Donegal (OR = 2.29, P= 0.0030, P(cor)= 0.0420). A higher frequency and a significantly higher homozygosity rate of this haplotype in Donegal are likely contributing factors to the higher prevalence of MS in Donegal compared with Wexford. The distribution of HLA class II alleles among Irish MS patients and controls establishes that there is heterogeneity in HLA class II associations with MS within Ireland.

The two main categories of pain, nociceptive and neuropathic, are caused by tissue damage and nerve damage respectively. Psychogenic pain is also described in the literature but it is becoming a pejorative term as the concept of central control of pain is now gaining momentum. There is considerable overlap in brain areas that deal with pain and where mood disorders develop. Some neurotransmitters, e.g. serotonin and noradrenaline, are involved in receiving and processing signals and regulate mood as well. It is no coincidence that many drugs used to treat mood disorders are effective when used for pain relief. This article highlights this interplay of neurotransmission and affective/pain symptomatology.

Although the numbers tested in this study were small the results suggest one of the factors accounting for the difference in MS prevalence across the island of Ireland is likely to be variation in the genetic predisposition to MS within the Irish population.

Fibromyalgia is a musculoskeletal pain disorder which predominantly affects women and is often associated with depression. Both conditions have much in common, so assessment and treatment of physical and mental health symptoms with dual-acting medications and other appropriate interventions would seem advantageous.