Understanding XDP through imaging,pathology,and genetics

The X-linked dystonia-parkinsonism (XDP) is a severe progressive, adult-onset X-linked endemic disorder in Filipinos, which is characterized by dystonic movements that start in the third of fourth decade, and replaced by parkinsonism beyond the 10th year of illness. Understanding the pathophysiology of XDP and development of rational therapies will depend on observations from imaging pathological and genetic studies. In this paper we summarize the results of these studies on patients with XDP. The cranial magnetic resonance imaging shows hy-perintense putaminal rim in both dystonic and parkinsonian stages, and atrophy of the caudate head or putamen in the parkinsonian stage. Neuropathological findings show atrophy of the caudate nucleus and putamen, with mild to severe neuronal loss and gliosis. In the neostriatum, the dystonic phase of XDP shows the involvement of striosomes and matrix sparing, while the later, i.e., p[arkinsonian phase, shows matrix involvement as well. In the dystonic phase, the loss of striosomal inhibitory projections lead to disinhibition of nigral dopaminergic neurons, perhaps resulting in a hyperkinetic state; while in the parkinsonian phase, severe and critical reduction of matrix-based projection may result in extranigral parkinsonism. Genetic sequencing of the XDP critical region in Xq13.1 has revealed an SVA retronsposon insertion in an intron of TAF1. This may reduce neuron-specific expression of the TAF1 isoform in the caudade nucleus, and subsequently interfere with the transcription of many neuronal genes, including DRD2. Findings from imaging, pahtology, and genetics studies are gradually shedding light on the pathophysiology of XDP, which hopefully will lead to mare rational and directed therapies.

A Randomized, double-blind, placebo-controlled study comparing the efficacy, safety and tolerability of levodopa-carbidopa versus placebo in patients with X-linked dystonia-parkinsonism (XDP)

BACKGROUND: XDP is an X-linked recessive disorder characterized by parkinsonism and dystonia described among Filipinos. Oral medications are frequently ineffective. Lately, DBS have been promising. However these are not generally available or affordable for the vast majority of patients. We then decided to evaluate the effectiveness of levodopa-carbidopa for XDP. OBJECTIVE: To compare the efficacy, safety and tolerability of levodopa-carbidopa vs. placebo in XDP patients. METHODS: After informed consent and randomization, the BFM and the UPDRS parts III and IV were performed at baseline and monthly up to 6 months. Patients were randomized to receive either levodopa-carbidopa at a starting dose of 125 mg levodopa/ day in 2 divided doses or corresponding placebo. Gradual uptitration was done to a maximum of 1000 mg levodopa/ day or until side effects appeared. Homogeneity of the characteristics of patients in the 2 groups was determined using Independent t-test and Chi-square test. To determine the significance of changes in the efficacy parameters within each group, Wilcoxon Matched Pairs Signed Ranks Test was used. To compare the scores of the different efficacy parameters of the 2 groups, Mann Whitney U Test was applied to the data. A p?0.050 was considered significant.RESULTS: A total of 107 patients were recruited. There were 13 screen failures, and 94 were subsequently enrolled. The baseline characteristics (age, duration of illness, baseline BFM and UPDRS (motor) scores were not significant between levodopa and placebo (age in years: 47 + 9.35 vs. 50 + 9.51; duration of illness in years 6.3 + 7 vs. 6.2 + 5.2; BFM score: 32.8 + 24.5 vs. 28.4 + 26.5; UPDRS score 29.9 + 20.7 vs. 34.8 + 26.8). There was a decrease in BFM scores from baseline to all follow-up periods in patients given levodopa but were statistically significant only on visit 2 and visit 9. In the placebo group, decrease in scores was also observed in some observation periods but no statistical significance was shown. A comparison of the 2 groups showed that the magnitude of decrease in the levodopa group was statistically greater than the placebo group on the second visit. There were no significant differences observed in all other follow-up periods. Both groups showed a decrease in UPDRS scores but significant decrease was observed in visits 2, 5, 6, 7, 9 of the levodopa group. While in the placebo group, a significant decrease was observed only on visit 2. Comparison of the 2 groups did not show any significant differences. There were 17 patients from the levodopa group who reported adverse events (most common: increased involuntary movements, nausea/ vomiting/ dizziness, headache, and generalized weakness. In the placebo group, there were 11 patients (most common: increased involuntary movements, abdominal pain). There were 9 patients who dropped out (levodopa: 4, placebo: 5). CONCLUSION: There was a significant decrease in the BFM and UPDRS scores in XDP patients given levodopa compared to placebo. Levodopa is a safe and effective drug that may be considered in patients with XDP. NOTE: This study was supported by an unrestricted grant by Torrent Pharma Philippines, Inc.

The unique phenomenology of sex-linked dystonia parkinsonism (XDP, DYT3, "Lubag")

Sex-linked dystonia parkinsonism (XDP, DYT3, "Lubag") is an adult-onset, progressive, debilitating movement disorder first described in Filipino males from Panay Island in 1975. XDP manifests predominantly as torsion dystonia, later combined with or sometimes replaced with parkinsonism. Within the Island of Panay, the preva-lence rate is highest in the province of Capiz, where 1:4000 men suffer from the disorder. There is a high degree of penetrance and generalization. While women often serve as carriers, XDP is not limited to men. An updated XDP Philippine registry (as of January 2010) has identified 505 cases, with 500 males and 5 females. While some report that females may carry a milder form of the disorder, in our experience, both sexes generally follow a similar progressive clinical course.