Progressive myoclonic epilepsy type 1

Progressive myoclonic epilepsy type 1 (PME type 1), also known as Unverricht-Lundborg disease (ULD) or EPM1, is a rare inherited neurological disorder characterized by the onset of stimulus-sensitive myoclonus and tonic-clonic seizures, typically beginning between the ages of 6 and 16 years. It is caused by mutations in the CSTB gene (cystatin B) on chromosome 21q22.3, most commonly a dodecamer repeat expansion in the promoter region of the gene. The disease primarily affects the central nervous system, leading to progressive myoclonus, epileptic seizures, and gradual cerebellar ataxia. The hallmark feature of ULD is action-sensitive and stimulus-sensitive myoclonus, which can be severely disabling and tends to worsen over time, particularly in the first several years after onset. Generalized tonic-clonic seizures also occur but may become less frequent with age and appropriate treatment. Patients typically develop progressive ataxia, incoordination, intentional tremor, and dysarthria. Cognitive function is relatively preserved early in the disease course, though mild cognitive decline may occur over decades. Unlike some other forms of progressive myoclonic epilepsy, ULD does not typically cause severe dementia or rapid neurological deterioration, and life expectancy, while reduced, has improved significantly with modern management. There is no cure for Unverricht-Lundborg disease. Treatment is symptomatic and focuses on seizure and myoclonus control. Valproic acid and clonazepam are commonly used antiepileptic medications, and levetiracetam has also shown benefit. Certain antiepileptic drugs, particularly phenytoin, should be avoided as they may worsen myoclonus and cerebellar symptoms. Piracetam and brivaracetam may be used as adjunctive therapies for myoclonus. Physical therapy, occupational therapy, and psychosocial support are important components of comprehensive care. The disease is most prevalent in Finland and other Baltic regions, though cases have been reported worldwide.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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