Most common types of idiopathic dystonias

What are the most common types of idiopathic dystonias? 

The classic primary torsion dystonia (DYT1) is much more common among Ashkenazi Jews and is transmitted by an autosomal dominant gene whose expression is extremely variable.

Patients with DYT1 dystonia often start in early childhood with distal dystonia, such as dystonic writer’s cramp or foot inversion.

Over several subsequent years the dystonia becomes more proximal and generalized.

In severe cases, the dystonia may cause not only abnormal postures but also the intense contractions of muscles resulting in muscle breakdown and myoglobinuria.

This severe, life-threatening dystonia is referred to as either dystonic storm or status dystonicus. 

Dopa-responsive dystonia (DRD) comprises a clinically and genetically heterogeneous group of disorders, manifested typically by generalized dystonia, with or without diurnal fluctuation, but with a robust improvement with levodopa.

Autosomal dominant GTP cyclohydrolase-1 deficiency, also known as Segawa disease, is the most studied form of DRD, but deficiencies in tyrosine hydroxylase, sepiapterin reductase, and other genetic abnormalities can interfere with the biosynthetic pathway of dopamine and result in the DRD phenotype. 

Paroxysmal dystonia encompasses a heterogeneous and relatively rare group of conditions.

One type is psychogenic dystonia.

The organic forms, whether sporadic or autosomal dominant, can be categorized as either kinesiogenic or nonkinesiogenic.

Mutations in the PRRT2 gene on chromosome 16 were recently identified in multiple families of different ethnicities affected by paroxysmal kinesiogenic dyskinesia with or without infantile convulsions.

Sudden movements precipitate attacks of kinesiogenic dystonia.

These attacks typically last less than 5 minutes and recur up to 100 times per day.

Anticonvulsants such as carbamazepine and phenytoin are usually effective in preventing the episodes. 

Three distinct mutations in the PNKD gene, previously referred to as the myofibrillogenesis regulator gene ( MR-1 ), have been identified as the causes of paroxysmal nonkinesiogenic dystonia.

In the nonkinesiogenic paroxysmal dystonia, the attacks are less frequent (three per day), last longer (minutes to hours), and often are triggered by alcohol, coffee, and fatigue. 

Sources

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