Autoimmune thyroid disease in childhood: a study of children and their families.

OBJECTIVE

To study the clinical and laboratory profile of children with autoimmune thyroid disease (AITD) and its familial prevalence.

DESIGN

Clinical and investigative evaluation of 96 children and adolescents 5 to 16 years old suspected of having AITD based on clinical and family data and similar assessment of parents and siblings of 30 confirmed cases of AITD.

SETTING AND SUBJECTS

Of these 96 cases, 66 were from a private clinic and 30 were institution based thyroid antibody positive with confirmed AITD. On initial testing 36 (55%) of 66 clinic cases were thyroid antibodies (ab) positive and 30 were (ab) negative. In 12 of 30 ab -ve cases retesting for antibodies by newer technique or FNAC confirmed AITD. Clinical and laboratory evaluation of 90 of a total of 106 parents and siblings of the 30 institution based cases.

METHODS

Clinical evaluation with goiter grading by WHO criteria was done in all. Family history of thyroid disease was inquired for in all. Clinical examination and thyroid antibody status was assessed in 90 family members as stated above. Thyroid antimicrosomal (AMA) and antithyroglobulin (ATG) antibodies were tested by standard hemogglutination kits. Titers of > 1:100 considered +ve for children and >1:400 for adults. Thyroid (ab) could be tested in ten of the ab-ve cases by ECI technique on follow up. Bone age was assessed. Ultrasonographic or TCM 99 scanning of thyroid gland and FNAC were done as indicated.

RESULTS

Of the 96 children suspected to have AITD, thyroid antibodies were positive in high titers in 66 (36+30) cases (69%) on initial testing but with more sensitive ECI technique significant antibody titres were detected in 10 more cases (79%) and FNAC confirmed AITD in 2 more subjects (total 78 - initial 66 + 12). F:M ratio was 2.9:1. Sixty one per cent of children were between 6 to 12 years of age; mean age 10.12+/-2.9 years. Seventy seven per cent had hypothyroidism, 10% had thyrotoxicosis and only 13% were euthyroid. Family history of thyroid disease was elicited in 33% of the series. Survey of 90 parents and siblings of the institution based group revealed, euthyroid goiters in 17%, subclinical hypothyroidism in 10% and significant AMA titers in 43% (65% of mothers, 30% siblings and 43% fathers).

CONCLUSION

Juvenile AITD is a common cause of acquired thyroid disease in children above 5 years of age with a 3-fold higher prevalence in girls. The manifestations are heterogeneous. Hypothyroidism was most common (77%), euthyroid goiters (13%) and thyrotoxicosis (10%) were less frequent. Familial aggregation was noted in adult family members (33%) with positive thyroid antibodies in 65% of mothers. Sibling affection was less frequent. The familial and genetic implications of AITD are important; diagnosis of AITD in children may also help detect subclinical disease in adult family members.