HLA typing and immunological characterization of young‐onset diabetes mellitus in a Hong Kong Chinese population

SUMMARY Aims  A study of the Hong Kong Chinese showed that the majority of subjects with young‐onset diabetes (age of diagnosis < 35 years) present with a phenotype suggestive of Type 2 diabetes mellitus, although up to 50% subsequently need insulin treatment. The aim of this study was to use a combination of clinical, genetic and immunological markers to characterize the disease phenotype further in such individuals and to determine whether the requirement for insulin is the result of autoimmune disease.Methods  One hundred and thirty‐seven Hong Kong Chinese with young‐onset diabetes were studied, irrespective of their mode of presentation. The subjects were typed for alleles of the HLA‐DR and ‐DQ genes and investigated for the presence of autoantibodies to glutamic acid decarboxylase (GAD). Plasma C‐peptide concentration and requirement for insulin were also determined.Results  One hundred and three subjects presented with a syndrome resembling Type 2 diabetes, while 34 presented with Type 1 diabetes. Of the former group, 35 patients (34.0%) were insulin‐deficient, 16 (15.5%) were insulin‐treated and seven (6.9%) were positive for GAD autoantibodies. Among the GAD‐positive su