Increasing incidence of childhood Graves' disease in Hong Kong: a follow-up study

Childhood Graves' disease has been reported to be rare but preliminary epidemiological data on its incidence appeared to be high in Hong Kong Chinese children. The aim of this study is to determine the incidence of childhood Graves' disease in Hong Kong and to analyse whether there is an increasing trend of the incidence.

We established a registry of childhood Graves' disease at our centre to collect cases from four districts in Hong Kong. The diagnosis of Graves' disease was based on clinical features, diffused enlargement of thyroid gland, raised free thyroxine or triiodothyronine levels, suppressed TSH levels, and the presence of thyroid receptor antibodies. Confirmed cases of Graves' disease who resided in any of the four districts were used to calculate the incidence for the study period between 1989 and 1998.

One hundred and eighteen Chinese children under 15 years of age had a confirmed diagnosis of Graves' disease during the study period from January 1989 to December 1998. There were 11 boys and 107 girls giving a male to female ratio of 1 : 9.7. The overall incidence rates were 3.2/100 000/year and 6.5/100 000/year for the two periods 1989-93 and 1994-98, respectively. The incidence rates for girls have increased significantly (P < 0.001) from 3.8/100 000/year in 1989 to 14.1/100 000/year in 1998. The current incidence of childhood Graves' disease in our population is about eight times that reported in Danish children.

This study confirms the high incidence of childhood Graves' disease in Hong Kong and documents an increasing trend for girls. Further studies are required to reveal possible genetic or environmental factors responsible for such epidemiology in Hong Kong Chinese children.