Dermatology - Introduction
From Iusmicm
Revision as of 20:10, 12 October 2011 by 134.68.138.157 (Talk)
Contents |
Motivation
1. The skin is the biggest, thus most important organ 2. Skin diseases account for 17% of all primary care visits
Objectives
- Basic principles
- Introduction to dermatologists
- Common skin problems
- Complexity of dermatologic disorders
Expectations
- Structure and function of the skin
- History and physical examination
- Recognize the clinical (and histologic) hallmarks of diseases discussed
- Know how and when to refer a patient
Structure and Function
- Epidermis:
- Has keratinocytes, melanocytes, and langerhans cells
- Dermis:
- Has fibroblasts and blood vessels
- Subcutaneous
Keratinocytes
- Barrier Function: form the stratum corneum
- Produce cytokines and inflammatory molecules
- Produce antimicrobial proteins and lipids
- Metabolize drugs
- Arm skin:
- Finger skin:
Melanocytes
- Produce pigment
- Pigment protects against ultraviolet radiation
- Vitiligo: loss of melanocytes through autoimmune destruction
Langerhans cells
- Macrophage-like cells in epidermis
- Important for antigen recognition
Fibroblasts
- Found in the dermis
- Produce collagen and ground substance
Vocabulary
- Important for proper communication of observations
- Primary versus Secondary lesions
- Primary lesion: basic lesion that defines a disease process
- Secondary lesion: lesions that evolve during the skin disease process or are created by scratching or infection
Primary lesions
Macule / Patch
- Circumcised, flat (non-palpable), varies in color
- Discoloration: brown, blue, red, hypopigmented
- Large macules (~> 2cm) are called "patches"
Papule / Plaque
- Elevated, solid, 0.5-1 cm diameter
- Larger is a plaque
- Confluent papules are called "plaques"
- Can vary in color
- Note that if it is circumscribed it is a nodule
- Papules:
Nodule / Tumor
- Circumscribed, elevated, solid, 0.5-1 cm diameter
- Larger is a tumor
- Nodule:
- Tumor:
Wheal
- Firm, edematous plaque
- From infiltration of the dermis with fluid
- Wheals are transient, may only last hours
- http://itsmysocalledlife.files.wordpress.com/2009/02/190px-urtikaria_fuss.jpg%3Fw%3D190%26h%3D143
Pustule
- Circumscribed collection of leukocytes and free fluid, varies in size
Vesicle / Bulla
- Circumscribed collection of free fluid up to 0.5 cm diameter
- Bulla is over 0.5 cm diamter
- Vesicles:
- Bullae:
Secondary Lesions
Scales
- Excess dead epidermal cells that are produced by abnormal keratinization and shedding
Crusts / Erosions
- Crust: collection of dried serum and cellular debris (a scab)
- Erosion: focal loss of epidermis
- Do not penetrate below the dermal-epidermal junction and thus do not scar
Escoriations
- Erosion caused by scratching
- Often linear
Ulcers
- A focal loss of epidermis AND DERMIS
- Ulcers heal with scarring.
Fissure
- Linear loss of epidermis and dermis with sharply defined, vertical walls
Atrophy
- Depression in the skin from thinning of the epidermis or dermis
- http://mizzouderm.com/uploads/4/4/2/3/4423869/4212698_orig.jpg?214
Scar
- Abnormal form of connective tissue implying dermal damage.
- After an injury scars are initially thick and pink and become white and atrophic with time.
Special Lesions
Comedone
- Plug of subaceous and keratinaceous debris lodged in the opening of an hair follicle.
- The follicle opening may be widened (blackhead) or narrowed (whitehead).
Lichenifcation
- Area of thickened epidermis induced by scratching
- Skin lines are accentuated so that the surface looks like a washboard
Burrow
- Narrow, elevated tortuous channel in the skin, created by a parasite
- Scabies
Milia
- Small cysts under the skin; have walls containing epidermis
- Associated with scarring
Cyst
- Circumscribed with wall and lumen; may contain solid matter or fluid
Telangiectasia
- Dilated superficial blood vessels
- Also called spinder angiomas
- http://www.nytimes.com/imagepages/2007/08/01/health/adam/2998Telangiectasialegs.html
Petechiae / Purpura
- Petechiae: circumscribed deposit of blood, < 0.5 cm diameter
- Purpura: circumscribed deposit of blood, > 0.5 cm diameter
- Petechiae
- Purpura: