This investigation reports the prevalence and clinical profile of subacute 
sclerosing panencephalitis in two developed cities of southern China. A 
territory-wide survey was conducted to identify all subacute sclerosing 
panencephalitis cases diagnosed during 1988-2002 in Hong Kong and Macau. 
Altogether, 10 cases (male:female = 7:3) were identified of whom six were still 
alive. The prevalence rate of subacute sclerosing panencephalitis in Hong Kong 
and Macau in 2002 was 1 per million total population or 5.5 per million 
children. The mean age of presentation was 9.4 years (range = 4-14 years). 
Presenting features included myoclonus (60%), deterioration in school 
performance (30%), and transient visual impairment (10%). The clinical course 
was highly variable. Most had subacute course, but two deteriorated rapidly and 
died within 6 months. Seven children had measles infection, and the majority of 
infection (86%) occurred during the world measles epidemic in 1988. The mean 
interval between measles infection and onset of subacute sclerosing 
panencephalitis was 6.5 years (range = 3-11 years). There has been an increasing 
trend of subacute sclerosing panencephalitis in southern China after the measles 
outbreak in 1988. Active surveillance of subacute sclerosing panencephalitis for 
those with measles infection during the 1988 outbreak is necessary to conduct 
multicenter drug trials for this devastating disease.