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myxedema; thyroid dermopathy (includes myxedema coma)

Hypothyroidism which first appears in older children or adults Etiology: 1) removal or loss of functioning thyroid tissue 2) pretibial myxedema nearly always associated with Graves disease [5] - tobacco use may increase risk of pretibial myxedema [3] 3) less frequently occurs with Hashimoto's thyroiditis [7] Pathology: - accumulation of mucopolysaccharides (hyaluronic acid) in connective tissue throughout the body leads to skin changes & non-pitting edema * histopathology images [5,6] Clinical manifestations: 1) relatively hard, not-pitting edema of the subcutaneous tissue - most often confined to the pretibial area (pretibial myxedema) - firm, but compressible indurated woody plaques - occurs 1-2 years after onset of Graves disease [2] - some patients may develop elephantiasis [3] 2) dryness & loss of hair 3) subnormal temperature 4) hoarseness 5) muscle weakness, fatigue 6) slow return of a muscle after a tendon jerk to the neutral position 7) cognitive impairment: confusion, disorientation [4] * pretibial myxedema images [5,6,8] Laboratory: - thyroid function tests - serum TSH is high* ' - serum thyroxine is low* - serum sodium: hypnoatremia* (generally not severe) * exception is pretibial myxedema of Graves disease - values dependent upon treatment status Management: - primary therapy is thyroxine* (T4) - treatment is often administered intravenously, since there may be edema of the gut wall that limits oral absorption [4] - treatment with T3 (Cytomel) is controversial - treat underlying precipitating factors - topical glucocorticoid [6] - compression stockings [6] - smoking cessation [3] * exception is pretibial myxedema of Graves disease

Specific

myxedema coma; hypothyroid coma

General

thyroid disease

References

  1. Stedman's Medical Dictionary 24th ed, Williams & Wilkins, Baltimore, 1982
  2. Cotran et al Robbins Pathologic Basis of Disease, 5th ed. W.B. Saunders Co, Philadelphia, PA 1994 pg 1125-26
  3. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17. American College of Physicians, Philadelphia 2009, 2012, 2015
  4. Kim J Myxedema N Engl J Med 2015; 372:764. February 19, 2015 PMID: 25693016 http://www.nejm.org/doi/full/10.1056/NEJMicm1403210
  5. vonHilsheimer GE, Elston DM Medscape: Pretibial Myxedema http://emedicine.medscape.com/article/1103765-overview
  6. DermNet NZ: Pretibial myxoedema (images) http://www.dermnetnz.org/dermal-infiltrative/pretibial-myxoedema.html
  7. Fatourechi V Pretibial myxedema: pathophysiology and treatment options. Am J Clin Dermatol. 2005;6(5):295-309. PMID: 16252929
  8. Xie F, Johnson EF, Youssef MJ Thyroid Dermopathy and Acropachy Mayo Clinic Proceedings, 2022. 97(12):2314-15 https://www.mayoclinicproceedings.org/article/S0025-6196(22)00469-4/fulltext
  9. Wikipedia: Myxedema https://en.wikipedia.org/wiki/Myxedema