GM2 Gangliosidosis. Childhood subacute form. Hexosaminidase A deficiency.
Incidence
Approximately 20 patients have been reported. AR condition. No ethnic prevalence.
Clinical Characteristics
Onset is generally between age 3 and 6 years and deterioration is severe and rapid. Neurological signs are those with diffuse encephalopathy. These include progressive loss of speech, dysarthria, walking difficulties due to spastic paraparesis with pyramidal signs and cerebellar ataxia. Generally there is such combination of these signs. Dystonia and choreoatethosis also has been reported. Occasionally they may be startling response. Tonic clonic or myoclonic seizures and myoclonus are prominent features in some children. Irritability and aggressively and periods either of adinamia, apathy and desinterest or bizarre behavior may occasionally be observed as early signs. Mental deterioration is always present but may not be obvious initially. Loss of vision and retinal changes are inconstant or when present are likely to have developed late. Optic atrophy, macular cherry red spots and pigmentary degeneration in the retina all has been described. Signs of denervation atrophy in the EMG has been recorded. Nerve conduction velocity and CSF is normal. Neuroimaging does not help. After a period of three to ten years, the patient is usually bed-ridden and demented. A few patients with an onset at two to three years of age have a rapid downhill course, have cherry red spots and startling response as in Tay-Sachs disease. They may represent compounded heterozigotes with B-1 and Tay-Sachs.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB-W, EB-F. Hexosaminidase A deficiency.