The myxedema is edema or "swelling" nonpitting skin, especially the skin of the face, giving it a rough appearance and accompanying hypothyroidism. Hypothyroidism is a disease characterized by a decrease in circulating thyroid hormones.
The term "myxedema" is also used to refer to a condition of advanced or severe and untreated hypothyroidism. The skin contains several proteins complexed with polysaccharides, hyaluronic acid and chondroitin sulfuric acid. In hypothyroidism, these complexes accumulate and promote sodium and water retention, causing a characteristic diffuse and non-depressible edema, which is called myxedema.
Before and after treatment for myxedema (Source: Unknown author / Public domain via Wikimedia Commons)
This accumulation of mucopolysaccharides also occurs in the larynx and is the cause of the hoarseness that often accompanies hypothyroidism. The skin is dry and cold, the hair is brittle with loss of shine and there is usually hair loss from the scalp and from the side of the eyebrows.
Pretibial myxedema or thyrotoxic dermopathy is characteristic of Graves disease, and these patients invariably also present with ophthalmopathy.
It is a non-depressible edema that can be nodular, discoid, and even polypoid. The skin in the pretibial area takes on an orange peel appearance and is thickened.
Some authors classify myxedema into various types according to the time of its appearance, the duration and extent. Others directly associate it with congenital problems related to the thyroid gland, hypothyroidism, and pretibial myxedema related to thyrotoxicosis.
The so-called "myxedematous coma" or the "myxedematous crisis" is the most severe form of hypothyroidism, with a high mortality rate. It can be triggered by exposure to cold, sepsis, by the use of sedative or narcotic anesthetics, and / or the suppression of replacement therapy with thyroid hormones, among others.
Hypothyroidism and myxedema
Hypothyroidism involves a reduction in circulating thyroid hormones. The decrease in thyroid hormones can occur due to failures in the synthesis of these hormones or failures in the axis of stimulation of the synthesis or hypothalamic-pituitary-thyroid axis.
Hypothyroidism can be congenital or acquired in origin. Among those of acquired origin are Hashimoto's thyroiditis, severe iodine deficiency, lymphocytic thyroiditis, surgical resection and failure of hormone replacement, radiation therapy for head and neck tumors, among others.
Among the acquired causes are those of central origin due to alteration of the hypothalamus (TRH) or pituitary (TSH) and drugs such as, for example, inorganic iodine, amiodarone, thioamides and lithium.
Growth of the thyroid gland, characteristic of hypothyroidism (Source: http://www.scientificaimations.com / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0) via Wikimedia Commons)
The symptoms of hypothyroidism can be summed up as slow thinking, lethargy, dry and cold skin. The skin sometimes turns a yellow-orange color, as thyroid hormone is required to convert carotenes to vitamin A.
In addition, there may be weight gain, constipation, menorrhagia, decreased libido, and intolerance to cold.
Among the signs the following can be described: slowness in speaking, hypokinesia, thick and flaky dry skin, brittle and sparse dry hair, dry nails with longitudinal striae, cardiac functional alterations, depression, among others.
Among the skin alterations is edema, which generally affects the face. It acquires a coarse appearance, is puffy, edematous, with rounded and periorbital edema.
The edema does not leave pitting and is called myxedema, being characteristic of hypothyroidism, but not exclusive. This edema includes the lips, tongue, and larynx.
With the administration of thyroid hormones, the protein complexes of mucopolysaccharides responsible for myxedema are mobilized, diuresis increases, and myxedema disappears.
Graves disease and myxedema
Graves' disease is one of the most frequent causes of hyperthyroidism, it is accompanied by a symmetrical goiter with a gland that can triple its weight. Most of these patients have an antibody against the TSH receptor site on the thyroid follicles.
These patients present with the symptoms of hyperthyroidism that include increased alertness, emotional lability, nervousness, irritability, palpitations, great appetite and weight loss, increased frequency of bowel movements, and intolerance to heat.
Signs include hyperkinesis, proximal muscle weakness, fine tremor, periorbital edema, exophthalmos, tachycardia, atrial fibrillation, dyspnea among other findings. The classic triad of Graves' disease is hyperthyroid goiter, exophthalmos, and pretibial myxedema.
Peritibial myxedema (Source: Herbert L. Fred, MD and Hendrik A. van Dijk / CC BY (https://creativecommons.org/licenses/by/2.0) via Wikimedia Commons)
However, not all patients with Graves disease have pretibial myxedema. Pretibial myxedema appears in the region of the skin that covers the tibia or pretibial region. In this area the skin takes on an orange peel appearance. This myxedema can be nodular, discoid, or polypoid.
Classically, from the clinical point of view, infiltrated plaques of firm or indurated consistency appear, erythematous, which can acquire a purplish color. A dilation of the orifices of the hair follicles is observed, giving the appearance of "orange peel".
Myxedema or "thyroid dermopathy" may have other clinical presentations than the classical form previously described. Between these presentations it can appear in the lower extremities as a diffuse myxedema with small papules around the hair follicles.
Another form includes well-differentiated and symmetrically distributed nodules on both extremities, with a shiny purplish or brown surface, which may be slightly tender to the touch.
Sometimes myxedematous changes can extend to the surface of the skin covering the patella and to the feet.
References
- Flores, SM, Hidalgo, LG, & Topete, RO (2011). Atypical clinical presentations of pretibial myxedema. Dermatology Revista Mexicana, 55 (6), 347-351.
- Fatourechi, V. (2005). Pretibial myxedema. American journal of clinical dermatology, 6 (5), 295-309.
- Chen, JJ, & Ladenson, PW (1987). Euthyroid pretibial myxedema. The American journal of medicine, 82 (2), 318-320.
- Hammer, GD, & McPhee, SJ (2014). Pathophysiology of disease: An Introduction to Clinical Medicine 7 / E. McGraw-Hill Education.
- Hammer, GD, & McPhee, SJ (2014). Pathophysiology of disease: An Introduction to Clinical Medicine 7 / E. McGraw-Hill Education.