Aspects of beta cell and thyroid autoimmunity in children

Sammanfattning: The two most common autoimmune endocrine diseases in children are autoimmune thyroiditis (AIT) and Type 1 (insulin-dependent) diabetes mellitus (IDDM). Autoantibodies (ab) can be found several years before clinical diagnosis in both diseases. The aims of this study were to investigate the prevalence of thyroid ab in children with IDDM and in children with allergic diseases; to study islet ab and thyroid ab in schoolchildren prior to and after MMR vaccination, and 3 years later; and to investigate the prevalence of islet ab in cord blood of children born to mothers later developing IDDM (group I), and in children later developing IDDM (group II) compared to healthy controls. Thyroid peroxidase ab were found in a higher prevalence among IDDM children; 38% (20/52), and allergic children; 11% (16/140), compared to controls; 5% (20/370). Children with rubella antibodies before vaccination had higher levels of ICA than the rubella seronegative children. In contrast, thyroid ab levels and prevalences were lower among children with antibodies against measles, mumps, or both prior to vaccination than in children without those antibodies. No evidence was found that MMR vaccination in adolescence may trigger autoimmunity. The longitudinal study of ab over 3 years revealed a turnover of seropositive subjects for all investigated ab except glutamic acid decarboxylase ab. The prevalence of islet ab in cord blood was 58% (14/24) in group I, and 17% (14/81) in group II compared to 4% (12/320) among healthy controls. All ab-positive children in group I had mothers positive for the analogous ab while maternal ab were only found in 2 of the mothers of the ab-positive children in group II. These data demonstrate that islet ab are present in some newborns who later develop IDDM. It is concluded that thyroid ab and islet ab positivity may be transient occurring in many more individuals than is suggested by findings in isolated cross-sectional prevalence investigations, that natural infections may reduce thyroid autoimmunity and that the autoimmune process leading to IDDM may be initiated in utero.