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[Hereditary essential myoclonus. Report of a family]
R S Alves1, E R Barbosa, J C Limongi
1Clínica Neurológica, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (FMUSP), Brasil.
Abstract:
The occurrence of myoclonic and dystonic movements as an isolated expression of a neurologic condition of hereditary pattern have been scarcely described in literature. For this entity some authors proposed the denomination "hereditary myoclonic dystonia" while others prefer the use of the expression "hereditary essential myoclonus". We present a family in which this unusual association of abnormal movements affected several members in three generations. The propositus patient is a 14-year-old girl who have noticed the dystonic movements by 7 years of age and the myoclonic ones by 13 years of age, with a slow progression. There was no reference about the effect of alcohol (abstemious patient). There was a family history of similar cases. The supplementary investigation (seric dosage of cupper, ceruloplasmine, T3, T4, TSH; acanthocytes search; CSF examination; CT scan and MRI of the head) did not show any abnormality. Clonazepam was the only medication that lead to a clinical improvement, reducing both movements.
Insights
This study describes hereditary myoclonic dystonia, a rare inherited neurological disorder. Clonazepam effectively reduced symptoms in affected family members, offering a potential treatment avenue.
Area of Science:
- Neurology
- Genetics
- Movement Disorders
Background:
- Hereditary myoclonic dystonia is rarely documented as an isolated neurologic condition.
- Existing literature lacks a consensus on terminology, with terms like "hereditary myoclonic dystonia" and "hereditary essential myoclonus" proposed.
Observation:
- A family spanning three generations presented with a rare combination of myoclonic and dystonic movements.
- The propositus, a 14-year-old girl, experienced dystonic movements from age seven and myoclonic movements from age thirteen, with slow progression.
- Family history revealed similar cases, suggesting a hereditary pattern.
Findings:
- Comprehensive investigations, including blood tests (copper, ceruloplasmin, thyroid function), acanthocyte search, cerebrospinal fluid analysis, CT, and MRI, revealed no abnormalities.
- Clonazepam demonstrated clinical efficacy, significantly reducing both myoclonic and dystonic movements.
Implications:
- This case series expands the understanding of hereditary myoclonic dystonia, highlighting its presentation and inheritance pattern.
- Clonazepam emerges as a promising therapeutic option for managing this rare movement disorder.
- Further research is warranted to elucidate the genetic basis and pathophysiology of this condition.