myxedema; thyroid dermopathy (includes myxedema coma)

Introduction

Hypothyroidism which first appears in older children or adults

Etiology

• removal or loss of functioning thyroid tissue
• pretibial myxedema nearly always associated with Graves disease
  • tobacco use may increase risk of pretibial myxedema
• less frequently occurs with Hashimoto's thyroiditis

Pathology

• accumulation of mucopolysaccharides (hyaluronic acid) in connective tissue throughout the body leads to skin changes & non-pitting edema

* histopathology images

Clinical manifestations

• 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
  • some patients may develop elephantiasis
• dryness & loss of hair
• subnormal temperature
• hoarseness
• muscle weakness, fatigue
• slow return of a muscle after a tendon jerk to the neutral position
• cognitive impairment: confusion, disorientation

* pretibial myxedema images

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
• treatment with T3 (Cytomel) is controversial
• treat underlying precipitating factors
• topical glucocorticoid
• compression stockings
• smoking cessation

* exception is pretibial myxedema of Graves disease

More general terms

• thyroid disease

More specific terms

• myxedema coma; hypothyroid coma