X-linked dystonia parkinsonism: clinical phenotype, genetics and therapeutics.
The clinical phenotype of X-Linked Dystonia Parkinsonism (XDP) is typically one that involves a Filipino adult male whose ancestry is mostly traced in the Philippine island of Panay. Dystonia usually starts focally in the lower limbs or oromandibular regions, then spreads to become generalized eventually. Parkinsonism sets in later into the disease and usually in combination with dystonia. /DYT3/ and /TAF1/ are the two genes associated with XDP. An SVA retrotransposon insertion in an intron of /TAF1/ may reduce neuron-specific expression of the /TAF1/ isoform in the caudate nucleus, and subsequently interfere with the transcription of many neuronal genes. Polypharmacy with oral benzodiazepines, anticholinergic agents and muscle relaxants leaves much to be desired in terms of efficacy. The medications to date that may appear beneficial, especially in disabling dystonias, are zolpidem, muscle afferent block with lidocaine-ethanol and botulinum toxin type A. Despite the few cases undergoing deep brain stimulation, this functional surgery has shown the greatest promise in XDP. An illustrative case of XDP in a family depicts the variable course of illness, including a bout of "status dystonicus," challenges in therapy, reckoning with the social impact of the disease, and eventual patient demise. Indeed, there remains some gaps in understanding some phenomenological, genetic and treatment aspects of XDP, the areas upon which future research directions may be worthwhile.
Rosales RL