To the Editor: The review of dystonia by Tarsy and Simon (Aug.24 issue)1 contains misleading statements about dystonia 3 (alsoreferred to as X-linked dystonia–parkinsonism [XDP] andlubag), which is an important differential diagnosis in peopleof Filipino descent who present with dystonia, parkinsonism,or both. Table 2 of the article by Tarsy and Simon incorrectlystates that dystonia 3 is "endemic in Panay, Philippines." Althoughthe disorder originated through a founder effect on the Philippineisland of Panay, it is not "endemic" there. Rather, XDP occursin people of Filipino descent independently of their location.Several cases have been diagnosed in the United States, Canada,and Europe. The table also states that there is no known mutationin dystonia 3. In fact, there are several disease-specific sequencechanges (DSCs) within the TAF1/DYT3 transcript system, includingone in a transcribed exon (DSC3), that facilitate the unequivocalmolecular diagnosis of dystonia 3.2
Ulrich Müller, M.D., Ph.D. Institut für Humangenetik D-35392 Giessen, Germany
References
Tarsy D, Simon DK. Dystonia. N Engl J Med 2006;355:818-829. [Free Full Text]
Nolte D, Niemann S, Müller U. Specific sequence changes in multiple transcript system DYT3 are associated with X-linked dystonia parkinsonism. Proc Natl Acad Sci U S A 2003;100:10347-10352. [Free Full Text]
The authors reply: We thank Müller for pointing out thatTable 2 incorrectly lists the mutations for dystonia 3 as unknown.The mutations in the TAF1/DYT3 multiple transcript system shouldhave been listed.1 In the table, the mutation involved in dystonia8 was also incorrectly listed as unknown, whereas, in fact,mutations have been reported in the myofibrillogenesis regulator1 (MR-1) gene in association with this disorder.2,3
In their original report, Lee and colleagues described 28 Filipinomen with torsion dystonia that was thought to be X-linked, 23of whom were from the island of Panay.4 A subsequent study confirmedthat the prevalence of dystonia 3 in Panay was 13 times thatin the general Philippine population. The prevalence in theprovince of Capiz (which is on the island of Panay) is about1 case per 4500 men, which is 60 times that in the general population.5Lee et al. state that "the figures suggest that XDP is endemicin Panay, particularly in Capiz." We agree with these authors'use of the term "endemic," meaning a disease usually presentor always present in a region or population. Its presence elsewheredoes not contradict this designation.
David K. Simon, M.D., Ph.D. Daniel Tarsy, M.D. Beth Israel Deaconess Medical Center Boston, MA 02215 dtarsy{at}bidmc.harvard.edu
References
Nolte D, Niemann S, Müller U. Specific sequence changes in multiple transcript system DYT3 are associated with X-linked dystonia parkinsonism. Proc Natl Acad Sci U S A 2003;100:10347-10352. [Free Full Text]
Rainier S, Thomas D, Tokarz D, et al. Myofibrillogenesis regulator 1 gene mutations cause paroxysmal dystonic choreoathetosis. Arch Neurol 2004;61:1025-1029. [Free Full Text]
Lee HY, Xu Y, Huang Y, et al. The gene for paroxysmal non-kinesigenic dyskinesia encodes an enzyme in a stress response pathway. Hum Mol Genet 2004;13:3161-3170. [Free Full Text]
Lee LV, Pascasio FM, Fuentes FD, Viterbo GH. Torsion dystonia in Panay, Philippines. Adv Neurol 1976;14:137-151. [Medline]
Lee LV, Munoz EL, Tan KT, Reyes MT. Sex linked recessive dystonia parkinsonism of Panay, Philippines (XDP). Mol Pathol 2001;54:362-368. [Free Full Text]
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