What is the pathophysiology of carbuncle?

Carbuncle is a skin infection that involves multiple hair follicles grouped closely together. It is caused by bacteria, usually Staphylococcus aureus. They start as folliculitis (inflamed hair follicles), which then form furuncles (boils) that eventually merge together to form a carbuncle.

Pathogenesis:

- Entry of bacteria: S. aureus is the most common causative agent of carbuncles, though other bacteria, such as Streptococcus pyogenes or Pseudomonas aeruginosa, may also be involved. The bacteria enter the skin through breaks in the skin such as cuts, abrasions, or insect bites.

- Folliculitis: S. aureus multiplies within the hair follicles, causing inflammation and the formation of pustules (small pus-filled lesions). This is known as folliculitis.

- Furuncles: As the infection spreads and deepens within the skin, the furuncles develop. Furuncles are larger, deeper, and more severe than folliculitis, with central necrotic cores surrounded by inflamed tissue.

- Carbuncle formation: When multiple furuncles coalesce, they form a carbuncle. Carbuncles are characterized by a collection of interconnected furuncles that appear as a large, swollen, and tender area with multiple draining sinuses.

- Deeper tissue involvement: In severe cases, the infection can extend deeper into the skin and affect the underlying tissues, causing cellulitis (spreading bacterial infection of the connective tissues). Rarely, it may also involve the bloodstream, leading to bacteremia.

- Predisposing factors: Certain factors can increase the risk of developing carbuncles, including poor hygiene, obesity, diabetes, immune system disorders, malnutrition, and prolonged use of corticosteroids or other immunosuppressive medications.

Carbuncles require prompt treatment with antibiotics, pain management, and proper wound care to prevent complications.