16. Dermatology
Learning Objectives
- Identify the layers of the skin and explain their respective roles in protection, sensation, and immunity
- Distinguish between bacterial, fungal, viral, and parasitic skin infections based on clinical presentation and diagnostic findings
- Compare the pathophysiology of eczema and psoriasis and apply this understanding to treatment selection
- Recognize common pediatric dermatological conditions and describe age-appropriate management strategies
- Explain the indications, techniques, and postoperative care for core dermatological surgical procedures
- Apply the ABCDE criteria and other clinical tools to evaluate pigmented skin lesions
- Recall first-line pharmacological agents for common dermatoses as tested on USMLE Step 1 and Step 2
Quick Answer
Dermatology is the medical specialty focused on the diagnosis and treatment of diseases affecting the skin, hair, nails, and mucous membranes. The skin is the body's largest organ and serves as a physical barrier, immune interface, and sensory organ. Common conditions studied in this module range from infectious diseases (impetigo, tinea, herpes) to immune-mediated disorders (atopic dermatitis, psoriasis) to surgical conditions (skin cancer, Mohs surgery). A solid grasp of skin anatomy underlies all clinical reasoning in this specialty, and many dermatological presentations appear on USMLE examinations.
Topics at a Glance
| Topic | Key Focus | Importance |
|---|---|---|
| Introduction to Dermatology | Skin anatomy, diagnostic techniques, treatment overview | Foundation for all dermatology |
| Skin Infections and Infestations | Bacterial, fungal, viral, parasitic skin disease | High-yield for USMLE Step 2 |
| Eczema and Dermatitis | Atopic dermatitis, contact dermatitis, management | Common outpatient complaint |
| Psoriasis and Other Dermatoses | Autoimmune mechanism, types, biologics | Systemic comorbidities important |
| Pediatric Dermatology | Age-specific conditions, safety considerations | Frequent exam and clinical topic |
| Dermatological Surgery | Excision, Mohs surgery, chemical peels, perioperative care | Procedural knowledge for clinicians |
Key Terms
| Term | Definition | Related Concept |
|---|---|---|
| Epidermis | Outermost skin layer; provides barrier function and houses melanocytes and Langerhans cells | Skin anatomy |
| Dermis | Middle skin layer containing collagen, elastin, blood vessels, nerves, and hair follicles | Wound healing |
| Keratinocyte | Primary cell of the epidermis; produces keratin and turns over every 28 days (faster in psoriasis) | Psoriasis pathophysiology |
| Melanocyte | Pigment-producing cell located in the basal layer; loss causes vitiligo | Vitiligo, melanoma |
| Pruritus | Medical term for itch; mediated by histamine, cytokines, and nerve signals | Eczema, scabies |
| Erythema | Redness of the skin caused by vasodilation; blanches with pressure (unlike purpura) | Cellulitis, drug reactions |
| Vesicle | Small fluid-filled blister (less than 0.5 cm); seen in herpes, eczema, contact dermatitis | Bullous disorders |
| Plaque | Raised, flat-topped lesion greater than 1 cm; hallmark of psoriasis | Psoriasis |
| Koebner phenomenon | New skin lesions appearing at sites of trauma; seen in psoriasis, lichen planus, vitiligo | Psoriasis triggers |
| Atopy | Genetic tendency to develop IgE-mediated allergic diseases including eczema, asthma, and allergic rhinitis | Atopic triad |
| Dermatophyte | Fungal organism that infects keratinized tissue (skin, hair, nails); causes tinea infections | Tinea, onychomycosis |
| Mohs surgery | Staged excision technique that removes skin cancer layer by layer with real-time margin analysis | Skin cancer treatment |
Related Topics
Prerequisites: Basic histology (epithelial and connective tissue), immunology (T-cell mediated and IgE-mediated responses), microbiology (Staphylococcus, Streptococcus, dermatophytes, herpes viruses)
Related Topics: Rheumatology (psoriatic arthritis, lupus skin findings), Infectious Disease (sexually transmitted infections with skin manifestations), Pediatrics (neonatal skin conditions, childhood eczema), Oncology (melanoma staging, skin cancer screening)
Next Topics: Ophthalmology (periocular skin disease), Plastic Surgery (wound healing, skin grafting), Endocrinology (skin manifestations of thyroid disease, diabetes)