Boston's sign is the spasmodic lowering of the upper eyelid on downward rotation of the eye, indicating exophthalmic goiter.
[1] Similar to von Graefe's sign, it is observed in people with Graves-Basedow disease, a type of hyperthyroidism.
In this disease, the immune system attacks the thyroid gland and the soft tissues surrounding the eyes.
As a result, the eyes are often pushed forward in the eye sockets, a condition known as exophthalmos.
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