Phenotypic variability of DYT1-PTD: does the clinical spectrum include psychogenic dystonia?

Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous group of movement disorders, usually inherited in an autosomal dominant manner with reduced (30-40%) penetrance. The DYT1 gene on chromosome 9q34 is responsible for most cases of early limb-onset PTD. DYT1-PTD clinical spectrum is broad, as the disease may present with several degrees of body involvement and severity. We identified an Italian family with 4 members definitely affected by PTD, genetically diagnosed as carriers of the GAG mutation at DYT1 gene. Phenotype was homogeneous when considering the presentation at onset (limb involvement and early onset), the disease progression was variable; in the subjects of the last generation, the disease progressed to a severe, generalized PTD; in the remaining 2 subjects, dystonia presented with writer's cramp or upper body segmental dystonia of mild severity. One family member, carrier of the GAG mutation on DYT1 gene and mother of the most severely affected individual, presented with a clinically established psychogenic movement disorder resembling dystonia initially diagnosed as a severe generalized PTD. Psychogenic movement disorders are among the most controversial and challenging diseases to diagnose, in particular when the affected individual belongs to a family with an inherited movement disorder.