Rapid-onset dystonia-parkinsonism with ATP1A3 mutation and left lower limb paroxysmal dystonia

BACKGROUND

Rapid-onset dystonia-parkinsonism (RDP) is a disease characterized by an abrupt onset of dystonia accompanied by signs of parkinsonism and prominent bulbar symptoms.

CASE REPORT

We describe a case of a female patient, born after normal delivery, but diagnosed with mild intellectual disability at age 7. She presented with an abrupt onset of upper limb dystonia and bradykinesia without tremor in parkinsonism, as well as dysarthria and dysphagia caused by prominent bulbar symptoms, at age 9. She had normal findings on brain magnetic resonance imaging, electroencephalography, and blood examination but was diagnosed with a psychogenic disorder. At age 10, she developed left lower limb paroxysmal stiffness with pain, and at 14, she was hospitalized due to lasting paroxysmal symptoms. Whole-exome sequencing was performed for this index case and her parents, and a de novo missense variant c.829G > A, p.Glu277Lys in ATP1A3 was identified.

DISCUSSION

This RDP case highlights a rare clinical feature of paroxysmal dystonia that affects the lower left limb and develops after the abrupt onset of permanent dystonia. Currently, there are only three reported RDP cases associated with the same missense mutation, and we summarized the clinical features of all cases including ours, such as onset of age, time for stable, RDP score, relapse and exacerbation. Various symptoms owing to ATP1A3 mutation could develop as ATP1A3-related neurological disorders beyond classical phenotypes such as alternating hemiplegia of childhood (AHC) or RDP. Although RDP is extremely rare during childhood, it is important to understand its clinical characteristics in children.

ECHS1 deficiency-associated paroxysmal exercise-induced dyskinesias: case presentation and initial benefit of intervention

Paroxysmal exercise-induced dyskinesias (PED) are paroxysmal dyskinesias which manifest as dystonic movements brought on by sustained exercise. ECHS1 deficiency-induced EID was recently described by Olgiati et al. Our patient is an 8-year-old boy, who presented with intermittent episodes of stiffness and contractions affecting the legs which were always brought on by vigorous exertion. They began with curling of the toes and flexion, followed by stiffening of gait. These episodes were asymmetric, uncomfortable and often began in the left leg, often spreading to the right leg. They generally lasted for about 30-40 min. The phenomenology was noted to be dystonic affecting mostly the left leg, with equinus at the ankle and hyperextension at the knee. MRI of the brain showed regions of increased T2 and FLAIR signal and of T1 low signal in the globus pallidus bilaterally with mild diffusion restriction. Using Ambry's ExomeNext^TM, an integrated exome sequencing assay, the patient was found to be heterozygous for alterations in the ECHS1 gene: missense mutations in c.518C>T (p.A173V) and c.817A>G (p.K273E). After 3 months of treatment with a mitochondrial cocktail, the patient reported that his attacks were somewhat less frequent and less severe. We decided to continue the patient on the cocktail and prescribed clonazepam 0.5 mg 1 tab to be given, as needed, for acute dystonic episodes of severe degree. The missense mutation c.817A>G has never been associated with PED before. Further, we present the first case of ECH1-associated PED with initial symptomatic improvement with a mitochondrial cocktail.

Paroxysmal movement disorders

Paroxysmal dyskinesias represent a group of episodic abnormal involuntary movements manifested by recurrent attacks of dystonia, chorea, athetosis, or a combination of these disorders. Paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, paroxysmal exertion-induced dyskinesia, and paroxysmal hypnogenic dyskinesia are distinguished clinically by precipitating factors, duration and frequency of attacks, and response to medication. Primary paroxysmal dyskinesias are usually autosomal dominant genetic conditions. Secondary paroxysmal dyskinesias can be the symptoms of different neurologic and medical disorders. This review summarizes the updates on etiology, pathophysiology, genetics, clinical presentation, differential diagnosis, and treatment of paroxysmal dyskinesias and other episodic movement disorders.