Myxedema is a term used synonymously with severe hypothyroidism. It is also used to describe a dermatological change that can occur in hypothyroidism, and some forms of hyperthyroidism. This article discusses the dermatological changes. In this context, myxoedema refers to mucopolysaccharides deposition in the dermis.
This results in swelling of the affected area. One manifestation of myxoedema occurring in the lower limb is pretibial myxedema, a hallmark of Graves disease. Myxoedema can occur in Hashimoto's thyroiditis and other long-standing forms of hypothyroidism, as well as Graves disease, an autoimmune form of hyperthyroidism. The word myxoedema originates from μύξα, taken from ancient Greek to convey 'mucus' or 'slimy substance' and ὁίδημα for swelling. Signs and symptoms Myxoedema can occur in the lower leg and behind the eyes.
Cause Myxoedema is known to occur in various forms of hypothyroidism, and also in Graves' disease. One of the hallmarks of Grave's disease is pretibial myxedema, myxoedema of the lower limb. Myxoedema is more common in women than in men.
Myxedema can occur in: Hyperthyroidism, associated with pretibial myxedema and exophthalmos. Pretibial myxedema can occur in 1-4% of patients with Graves' disease, a cause of hyperthyroidism. Hypothyroidism, including Hashimoto's thyroiditis. Pathophysiology Myxedema describes a specific form of cutaneous and dermal edema secondary to increased deposition of connective tissue components.
These can include glycosaminoglycans, hyaluronic acid, and other mucopolysaccharides. The increased deposition of glycosaminoglycan is not fully understood, however two mechanisms predominate: Fibroblast stimulation. It is thought that fibroblast stimulation by the thyroid stimulating hormone receptor increases the deposition of glycosaminoglycan. This results in an osmotic edema and fluid retention. It is thought that many cells responsible for forming connective tissue react to increases in TSH levels. Lymphocyte stimulation.
In Basedow-Graves' thyroid disease, lymphocytes react against the TSH receptor. Lymphocytes react not only against thyroid receptors, but also any tissue with cells expressing the receptor. This can lead to tissue damage and scar tissue formation, explaining the deposition of glycosaminoglycans. References.
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