Acetylcholine receptor antibodies in the elderly and in Down's syndrome.

Serum antibodies to the acetylcholine receptor (anti-AChR) have been reported in Japanese individuals who were elderly or had Down's syndrome at frequencies of 18% and 24%, respectively. We have measured serum anti-AChR in 3 Caucasoid groups: 53 elderly patients (aged 65-92 years) with miscellaneous (non-myasthenic) disorders, 30 individuals with Down's syndrome, and 40 elderly patients (aged 71-93 years) known to have strongly positive thyroid autoantibodies. A raised titre (greater than 0.2 nmol/l) was confined to 3 patients in the third group (7.5%). We conclude that an increased frequency of anti-AChR antibodies is not a feature of Caucasians who are elderly or have Down's syndrome, and that, even in an elderly group with a high titre of another autoantibody, the frequency of anti-AChR is lower than in elderly Japanese individuals.