BACKGROUND AND PURPOSE: The prevalence of Huntington's disease (HD) among East Asians is less than one-tenth of that among Caucasians. Such a low prevalence may be attributable to a lack of carriers of specific predisposing haplogroups associated with the high instability of the Huntingtin gene (HTT). The aim of this study was to evaluate the association between specific HTT haplogroups and the occurrence of HD in a Thai population. METHODS: CAG-repeat sizes and HTT haplotypes were analyzed in 18 Thai HD patients and 215 control subjects. Twenty-two tagging single-nucleotide polymorphisms (tSNPs) were genotyped. RESULTS: Only 18 patients from 15 unrelated families were identified over the last 17 years. Pathological CAG-repeat alleles ranged from 39 to 48 repeats (43.5+/-3.0, mean+/-SD), and normal alleles ranged from 9 to 24 repeats (16.49+/-1.74). Only two of the chromosomes studied comprised intermediate alleles. Unlike the Caucasian data, all but 1 of the 22 tSNPs were not associated with the occurrence of HD. The predisposing haplogroups for Caucasian HD (haplogroups A1 and A2) are very rare in Thai patients (<4%). Both HD and normal chromosomes are commonly haplogroups A5 and C, in contrast to the case for Chinese and Japanese patients, in whom only haplogroup C was common in HD chromosomes. The frequency of CAG-repeat sizes of haplogroup A5 and C were also similarly distributed. CONCLUSIONS: HD chromosomes of Thai patients may arise randomly from each haplogroup, with a similar mutation rate. This rate is much lower than the CAG expansions from Caucasian HD haplogroups. These data suggest that the different mechanisms underlie CAG expansion in Thai and Caucasian patients.
Alleles ; Asian Continental Ancestry Group ; Haplotypes* ; Humans ; Huntington Disease* ; Mutation Rate ; Prevalence*

Objectives: To determine the prevalence of Thai demyelinating diseases regarding demographic data, symptoms and signs, associated diseases, disease progression, cerebrospinal fluid analysis and imaging findings. Methods: A multicenter retrospective study of 107 MS patients attending the Neurological Centers in Thailand during June and December 2004 was performed. Each had an initial diagnosis of demyelinating diseases. Results: From 107 patients, there were 78.5% female and 21.5% male with the female: male ratio of 3.7:1. The age at onset was 32.7±11.5 years. The mean disease duration was 3.8±5.1 years and the mean number of relapses was 4.6±4.4 with annual relapse rate of 1.5±1.3 times. None reported a family history of MS. Recurrent optico-spinal form was 27.1% followed by 17.8% of spinal form and 15% of western form of MS. The most common presenting symptom was visual impairment (51.4%). Only 24.1% demonstrated oligoclonal bands in CSF. The median score of EDSS at their latest visits was 3.0 with mean score of 3.8±3.0. Conclusions: MS in Thailand is different from Western countries. There were no occurrence of MS in families, higher incidence of visual impairment at onset, more common recurrent optico-spinal form and lower incidence of oligoclonal bands in the CSF.

DYT1 and DYT6 dystonias are the two most common genetic primary dystonias. However, they are rare in the Asian population and have never been reported in Thailand. DYT6 dystonia typically presents with craniosegmental dystonia with speech involvement, whereas DYT1 dystonia typically presents with lower limb dystonia, which tends to become generalized over time. Methods: Blood samples were collected from 14 patients with primary dystonia evaluated in five tertiary hospitals in Thailand. Genotyping of the TOR1A and THAP1 gene was performed. Results: Two patients were found to have a missense mutation, p.M143V (c.427A>G), in exon 3 of the THAP1 gene confirming the diagnosis of DYT6 dystonia. One patient was a woman who developed blepharospasm and lower cranial dystonia at the age of 38 years. Her dystonia spread to the neck and arm six months later. The other patient developed focal hand dystonia at the age of 34 years. The TOR1A mutation was not identified in any of these 14 patients.