Primary genetic dystonia and first episode of psychosis

To the Editor

The association of spontaneous dyskinetic movement disorders and psychosis in anti-psychotic naïve patients has been established (Pappa and Dazzan, 2009). In a high-risk population, baseline dyskinesia warrants thorough evaluation for psychosis (Callaway et al., 2014). We present a case of an adolescent with primary genetic dystonia (PGD) who developed an early-onset first episode of psychosis (FEP).

At 10 years of age, B was diagnosed with a PGD with superior intellect. She initially presented with facial dystonia, dysarthria, difficulty with handwriting, gait problems and bradykinesia. Genetic testing revealed 1.1 Mb duplication at chromosome 8p23.2 to 8p23.3. She was prescribed dopaminergic drugs for the movement disorder with no significant clinical improvement. At the age of 14 years, she exhibited negative symptoms of a prodromal psychotic illness followed by distressing auditory hallucinations and persecutory delusions. Movement disorder was the only identifiable risk factor for psychosis. She was treated with low-dose olanzapine and positive symptoms resolved in 4 weeks. The primary movement disorder symptoms were unaffected with olanzapine as evident by stable scores of 4 on Abnormal Involuntary Movement Scale.

PGD, which presents with dyskinesia, can be an independent risk factor for the development of FEP. These dyskinetic movements are biological predictor of pathogenesis intrinsic to psychosis. In the population with baseline movement disorders, the prevalence of psychosis is up to 20% (Callaway et al., 2014). Patients with PGD present with movement abnormalities hence are at high risk for the development of psychosis.

It is clinically pertinent to frequently screen patients with PGD for prodrome and symptoms of psychosis. Close clinical observation and cognitive behavioral therapy in suspected cases are advised. Longer duration of untreated psychosis are associated with worse clinical, functional and cognitive outcomes in FEP (Díaz-Caneja et al., 2015).

For the treatment of psychosis, it is prudent to consider lower doses of anti-psychotic medications with favorable extra pyramidal symptoms (EPS) side effects. The ratio of affinity for D₂ and 5-HT_2A receptors determines the EPS liability of these medications. EPS side effects could be hard to distinguish from primary dystonia itself.

Clinicians should periodically screen PGD patients for prodromal symptoms and psychosis and if appropriate refer to the specialized care. Larger scale studies controlling for confounding factors are necessary to establish a correlation of PGD and psychosis.