Which disease is characterized by the thinning of skin and easy bruising?

Cushing's disease is characterized by the thinning of skin and easy bruising due to an excess of cortisol in the body. This condition can lead to changes in the skin integrity as well as the underlying tissues. Cortisol affects the body's ability to produce collagen, a protein essential for maintaining skin's strength and elasticity. As a result, individuals with Cushing's disease often experience fragile skin that is prone to bruising, even from minor impacts.

In contrast, psoriasis is an autoimmune condition that leads to the rapid growth of skin cells, causing red, scaly patches, while eczema typically refers to a group of conditions causing inflammation and irritation of the skin. Dermatitis is a more general term covering inflammation of the skin but does not specifically denote the thinning of skin or easy bruising. Thus, Cushing's disease is uniquely associated with these particular symptoms, making it the correct choice.