Skin Diseases and Disorders

Cellulitis develops when bacterial infestation occurs on an injury or surgical wound, causing inflammation of the dermis and subcutaneous tissues. Gram-positive bacteria like Staphylococcus aureus and Streptococcus species are common culprits. S. aureus produces leukocidins, enzymes that kill white blood cells, leading to pus formation and purulent skin infections.

Ringworm is a cutaneous mycosis caused by dermatophytes that infect only the epidermis, hair, and nails. It develops as itchy, red circular patches requiring keratin for growth. Other fungal infections include subcutaneous mycoses, which penetrate deeper tissues, and systemic mycoses, which spread throughout the body.

Hair follicles are common entry points for bacterial infections. S. aureus infections may initially manifest as folliculitis, an infection of the hair follicle. If untreated, folliculitis can progress to furuncles or deeper abscesses called carbuncles. Understanding accessory structures of the skin hair and hair follicles helps explain how infections spread through these vulnerable areas.

Impetigo is a bacterial infection causing vesicles and pustules, often around the nose and mouth. In nonbullous impetigo, cysts and pustules rupture and become encrusted sores. Bullous impetigo forms large, fluid-filled blisters called bullae that measure at least 5 millimeters in diameter, representing a more severe presentation.

Scleroderma is an autoimmune connective tissue disorder characterized by abnormal skin thickening due to collagen overproduction. This causes significant changes in skin morphology and appearance. Unlike infectious skin diseases, scleroderma results from the immune system attacking the body's own tissues, leading to progressive fibrosis and hardening of affected skin areas.

Psoriasis is an autoimmune condition characterized by red, raised epidermal patches appearing as rashes with silvery scales that itch or bleed. Vitiligo, another chronic autoimmune condition, affects melanocytes and manifests as patches of pale skin due to loss of pigmentation. Both conditions result from immune system dysfunction rather than infection.

Warts are small skin growths caused by human papillomavirus transmitted through direct contact. Many HPV types exist, leading to various presentations including common warts, plantar warts, flat warts, and filiform warts. Each type affects different body areas and has distinct morphological characteristics, though all result from viral infection of skin cells.