Final answer:
Cutaneous small vessel vasculitis is an inflammatory condition of the skin's small blood vessels, leading to petechiae. It often involves a type III hypersensitivity reaction with immune complex deposition in blood vessels.
Step-by-step explanation:
Cutaneous small vessel vasculitis is a condition involving inflammation of the small blood vessels in the skin. This inflammation can lead to blood leaking from the damaged vessels, resulting in the appearance of petechiae, which are small red or purple spots on the skin. The underlying mechanisms may involve a type III hypersensitivity inflammatory reaction, which is induced by the formation of immune complexes and their subsequent deposition in tissues and blood vessels.
Conditions like cellulitis and erysipelas are bacterial skin infections that also affect the deeper layers of the skin such as the dermis, hypodermis, leading to inflammation and a painful, reddened, and warm area of the skin. However, cutaneous small vessel vasculitis specifically pertains to the vasculature within the skin.