In infants, the disease will usually manifest between the ages of 18 & 24 months as difficulty walking, muscle wasting and weakness, developmental delays, loss of vision and convulsions eventually leading to paralysis, dementia and death generally before the first decade. In adults, the disease almost always presents as a form of mental illness. In adults, the symptoms progress very slowly and may last for more than a decade. There is no treatment for any form of the disease, so care concentrates on alleviating some of the worse symptoms.