Infectious Diseases Affecting the Skin and Eyes Summary

The Skin and Its Defenses

• Surface Area: 1.5 to 2 sq meters; Thickness: 1.5 mm to 4 mm
• Key Layers: Epidermis, Dermis

Epidermis Features

• Stratum Corneum: Keratin-rich, water-repellent properties, replaced every 25-45 days
• Stratum Basale: Contains stem cells; source of epidermal cells

Dermis Characteristics

• Composed of connective tissue with nerves, blood vessels, lymphatics
• Contains follicles, sweat glands, and sebaceous glands

Natural Defenses of the Skin

• Antimicrobial Peptides: Disrupt bacterial membranes, maintain low microbiome count
• Sebum: Low pH, high lipid content inhibits pathogens
• Sweat: High salt, low pH
• Lysozyme: Enzyme in bodily fluids that disrupts bacterial cell walls

Normal Biota of the Skin

• Major normal biota includes Staphylococcus epidermidis, Propionibacterium acnes
• Diverse microbial populations, more dense in moist areas

Infectious Skin Diseases

• MRSA: Resistant Staphylococcus, causes localized lesions
• Impetigo: Bacterial, caused by S. aureus or S. pyogenes
• Cellulitis: Fast-spreading infection, often in lower leg
• Gas Gangrene: Caused by Clostridium perfringens

Common Skin Reactions

• Vesicular/Pustular Rash Diseases: Includes chickenpox, smallpox, hand, foot, and mouth disease
• Warts: Caused by human papillomaviruses; vary by type (seed, plantar)

Eye Anatomy and Defense

• Conjunctiva, Cornea: Protective membranes with lubricating secretions
• Tears: Contain enzymes and antibodies for protection
• Immune Privilege: Lower immune response to protect vision

Eye Infections

• Conjunctivitis: Symptoms vary (bacterial vs viral discharge)
• Keratitis: Serious infection, potential for corneal destruction
• Trachoma: Caused by Chlamydia trachomatis, major cause of blindness
• River Blindness: Chronic parasitic infection from Onchocerca volvulus