Immunodeficiency in Down's syndrome: relationship between presence of human thyroglobulin antibodies and HBsAg carrier status.

The relationship between the presence of hepatitis B surface antigen (HBsAg) and antibodies to human thyroglobulin (HTgAb) has been studied in 110 subjects with Down's syndrome (DS) from 4 months to 50 years of age and in 122 controls carefully matched for sex, age and socio-environmental conditions. The overall percentage of HBsAg carriers was 22.7 in DS and 6.6 in controls and that of HTgAb-positive subjects was 41.8 in DS and 19.7 in controls. In DS the frequency of HTgAb-positive subjects was very high, even in the youngest age groups in which the percentage of HBsAg carriers was relatively low; the latter thereafter showed a marked increase with age. A positive association between the presence of HBsAg and HTgAb was found only in the oldest age group of DS subjects. It is thus concluded that in DS the high frequency of HTgAb cannot be attributed to chronic hepatitis B virus infection. On the contrary, the presence of HTgAb might well represent an early "marker" of immunodeficiency and increased susceptibility to infection with hepatitis B virus.