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Cutaneous Manifestations of Endocrinologic Disease

»	How does endocrinologic disease cause skin disorders?
»	What is necrobiosis lipoidica?
»	Do all patients with necrobiosis lipoidica have diabetes?
»	Is necrobiosis lipoidica diabeticorum common in patients with diabetes?
»	Does glucose control affect necrobiosis lipoidica diabeticorum?
»	What other skin findings are associated with insulin resistance?
»	What does acanthosis nigricans look like?
»	Is diabetes the only condition associated with acanthosis nigricans?
»	What bacterial infections are more common in diabetic patients?
»	What are the most common fungal skin infections associated with diabetes?
»	Are there more dangerous fungal infections associated with diabetes?
»	Why are diabetic patients in ketoacidosis especially prone to mucormycosis?
»	What other skin disorders are commonly encountered in diabetic patients?
»	Describe the clinical manifestation of pretibial myxedema.
»	Why does treatment of Graves’ disease have no effect on pretibial myxedema?
»	What are the skin manifestations of hypothyroidism?
»	Why do hypothyroid patients have yellow skin?
»	Why do hypothyroid patients have thickened skin?
»	How does the myxedema of hypothyroidism differ from pretibial myxedema of Graves’ disease?
»	Are the skin changes of hypothyroidism reversible with thyroid replacement?
»	What are the skin manifestations of hyperthyroidism?
»	Which hormone gives the skin a darkened or tanned appearance?
»	What skin disease is associated with insulin-dependent diabetes, hypothyroidism, and Addison’s disease?
»	What skin findings are associated with glucocorticoid excess or Cushing’s disease?
»	Are the skin changes caused by excess glucocorticoids reversible?
»	Which hormones have the greatest effect on sebaceous glands and hair?
»	Are there medications and nutritional supplements that may cause acne?
»	What hormonal methods are available to treat acne?
»	What are xanthelasma?
»	What are eruptive xanthomas?
»	How do eruptive xanthomas differ from tuberous xanthomas?
»	What are the cutaneous features of acromegaly?
»	How does panhypopituitarism affect the skin?
»	How do you diagnose endocrine disease from skin findings?

Describe the clinical manifestation of pretibial myxedema.

Pretibial myxedema. A, Large indurated skin-colored plaques. B, A positive 'string sign' of mucin extending from the biopsy site to the surgical glove. (Panel B courtesy of Scott Freeman, MD.)

Fig. 36.3 Pretibial myxedema. A, Large indurated skin-colored plaques. B, A positive 'string sign' of mucin extending from the biopsy site to the surgical glove. (Panel B courtesy of Scott Freeman, MD.)

Pretibial myxedema is characterized by brawny, indurated plaques over the pretibial areas. These plaques may be skin-colored or have an unusual brownish-red color (Fig. 36-3A). On biopsy, the skin is infiltrated by mucinous ground substance (Fig. 36-3B). Pretibial myxedema is specific for Graves’ disease, a frequent cause of hyperthyroidism, but occurs in only 3% to 5% of patients with the disease. Pretibial myxedema is often associated with Graves’ ophthalmopathy (bulging eyes or exophthalmos) and acropachy (clubbed nails). Treatment of hyperthyroidism has no effect on pretibial myxedema.

Ai J, Leonhardt JM, Heymann WR: Autoimmune thyroid diseases: etiology, pathogenesis, and dermatologic manifestations, J Am Acad Dermatol 48:641–659, 2003.