How is hyperpigmentation of the skin in Addison disease characterized?

Updated: Mar 11, 2020
  • Author: George T Griffing, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

Hyperpigmentation of the skin and mucous membranes often precedes all other symptoms by months to years. It is caused by the stimulant effect of excess adrenocorticotrophic hormone (ACTH) on the melanocytes to produce melanin. The hyperpigmentation is caused by high levels of circulating ACTH that bind to the melanocortin 1 receptor on the surface of dermal melanocytes. Other melanocyte-stimulating hormones produced by the pituitary and other tissues include alpha-MSH (contained within the ACTH molecule), beta-MSH, and gamma-MSH. When stimulated, the melanocyte changes the color of pigment to a dark brown or black.

Hyperpigmentation is usually generalized but most often prominent on the sun-exposed areas of the skin, extensor surfaces, knuckles, elbows, knees, and scars formed after the onset of disease. Scars formed before the onset of disease (before the ACTH is elevated) usually are not affected. Palmar creases, nail beds, mucous membranes of the oral cavity (especially the dentogingival margins and buccal areas), and the vaginal and perianal mucosa may be similarly affected.

Hyperpigmentation, however, need not be present in every long-standing case and may not be present in cases of short duration. [13]


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