Familial progressive myoclonic epilepsy with Lafora bodies. Lafora disease.
Incidence
It is an autosomal recessive disease of adolescents. The gene has been mapped to chromosome six. More than sixty cases has been reported by 1980. It is inherited as autosomal recessive. It is distributed worldwide.
Clinical Characteristics
Seizures, polymyoclonus and dementia are the cardinal signs of this disease. It is an autosomal recessive disease of adolescents with rapid progressive course characterized by the presence of specific cytoplasmic inclusions (the Lafora bodies). These bodies are composed by polyglucosans in the neurons of the central nervous system. The biochemical defect is unknown. The average course of the disease is five years. Lafora bodies can be found in skin, liver and muscle. The mean age of onset is fourteen years (from 9 to 20 years) but few have begun in mid adulthood. A previous normal individual begin with tonic-clonic or myoclonic seizures, then polymyoclonus, or may present as isolated unexplained mental retardation. Seizures may precede other signs of the disease by several months or even years. The intention myoclonus has the same characteristic as the Umberricht-Lumdborg disease. The disease is rapidly incapacitating with mental deterioration constantly present but not always an early sign. Personality change and bizarre behavior may occur. Some 30 to 50 percent of cases have occipital seizures and visual hallucinatory phenomena. Cerebellar ataxia is always present. Optic atrophy may occur and deafness can be an early finding. Rigidity and exaggerated tendon reflexes may develop later in the disease. The EEG shows polyspike and slow wave complexes and progressive slowing background rhythms. Background activity may remain normal for several years. There is no photosensitivity. There may be giant somesthetic sensory evoked potentials. MRI reveal moderately cerebellar atrophy. Detection of Lafora bodies in the epithelium of sweat glands in biopsy specimens of the skin especially in the axillary skin and in the liver or muscle tissue remain as the only definite diagnostic test. The demonstration of typical inclusions in this tissues is not always possible. A negative biopsy does not exclude the diagnosis. There is no effective treatment. Clinical course generally goes for 2 to 10 years and most patients die by the age of twenty years.
Precipitants
Movements produce intention myoclonus.
Provocation Tests
no
Diagnostic Procedures
Detection of Lafora bodies in the epithelium of sweat glands in biopsy specimens of the skin especially in the axillary skin and in the liver or muscle tissue remain as the only definite diagnostic test. The demonstration of typical inclusions in this tissues is not always possible. A negative biopsy does not exclude the diagnosis. The EEG shows polyspike and slow wave complexes and progressive slowing background rhythms. There may be giant somesthetic sensory evoked potentials.