Interesting that you mention the thymus gland. I'm going to have a chest scan of my thymus. I have had symptoms of Myasthenia Gravis for many years. I tested positive for Cogan's lid twitch, enhanced ptosis (curtain sign), counting test to name a few. I have 4 other autoimmune diseases including Hashimoto's thyroiditis. There is a link between thyroid disease and MG. One study for instance finding 10% with MG had autoimmune thyroid disease.
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"Heterogeneous echogenicity of the thyroid gland is a non-specific finding and is associated with conditions diffusely affecting the thyroid gland. These include:
Hashimoto thyroiditis
Graves disease"*
*Radiopaedia - Heterogeneous thyroid echotexture