Hyperpigmentation of nails in primary adrenal insufficiency

Fingers of a 28-year-old White female with Addison's disease (underneath) compared with those of a female without Addison's disease (top).

Adrenal insufficiency caused hyperpigmentation (darkening) of the skin and the top half of the fingernails. The bottom half of the nails have hypopigmentation (lack of color); this is a result of the reduction in corticotropin (ACTH) secretion after starting treatment with glucocorticoids.