This female patient complains of palpitations , insomnia , weight loss inspite of polyphagia.

What is the leision in the picture? what is the most probable diagnosis?

pretibial myxedema of Graves' disease.

Pretibial myxedema (PTM) or, more appropriately, thyroid dermopathy is a term used to describe localized lesions of the skin resulting from the deposition of hyaluronic acid, usually as a component of thyroid disease. Although the condition is most often confined to the pretibial area, it may occur anywhere on the skin. It is nearly always associated with Graves disease.

read more on it from this link: Pretibial Myxedema