Dermatology - Introduction

From Iusmicm

Contents 1 Motivation 2 Objectives 3 Expectations 4 Structure and Function 4.1 Keratinocytes 4.2 Melanocytes 4.3 Langerhans cells 4.4 Fibroblasts 5 Vocabulary 5.1 Primary lesions 5.1.1 Macule / Patch 5.1.2 Papule / Plaque 5.1.3 Nodule / Tumor 5.1.4 Wheal 5.1.5 Pustule 5.1.6 Vesicle / Bulla 5.2 Secondary Lesions 5.2.1 Scales 5.2.2 Crusts (scab) / Erosions 5.2.3 Escoriations 5.2.4 Ulcers 5.2.5 Fissure 5.2.6 Atrophy 5.2.7 Scar 5.3 Special Lesions 5.3.1 Comedone 5.3.2 Lichenifcation 5.3.3 Burrow 5.3.4 Milia 5.3.5 Cyst 5.3.6 Telangiectasia 5.3.7 Petechiae / Purpura 6 Examples

[edit] Motivation

1. The skin is the biggest, thus most important organ
2. Skin diseases account for 17% of all primary care visits

[edit] Objectives

• Basic principles
• Introduction to dermatologists
• Common skin problems
• Complexity of dermatologic disorders

[edit] Expectations

• Structure and function of the skin
• History and physical examination (learn the vocab)
• Recognize the clinical (and histologic) hallmarks of diseases discussed
• Know how and when to refer a patient

[edit] Structure and Function

• Three parts: epidermis, dermis, and subcutaneous.
• Epidermis:
  • Has keratinocytes, melanocytes, and langerhans cells
• Dermis:
  • Has fibroblasts and blood vessels
• Subcutaneous

[edit] Keratinocytes

• Makes up most of the epidermis.
• Keeps in what should be in and out what should be out
• Barrier Function: form the stratum corneum
• Produce cytokines and inflammatory molecules
• Produce antimicrobial proteins and lipids; more potent than anything we can prescribe
• Metabolize drugs
• Arm skin:
• Finger skin:
  • Has different keratins than has the arm

[edit] Melanocytes

• Melanocytes determine how much melanin and therefore the pigmentation of the pt
• Produce pigment
• Pigment protects against ultraviolet radiation
• Vitiligo: loss of melanocytes through autoimmune destruction
  • 

[edit] Langerhans cells

• Macrophage-like cells in epidermis
• Important for antigen recognition
• About 1/3 of all T cells have been educated in the skin
• 
• 
• 

[edit] Fibroblasts

• Found in the dermis
• Produce collagen and ground substance
• Keloid scar is an example of excessive fibroblast activity
• 
• 
• 
• 
• 
• 

[edit] 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

[edit] Primary lesions

• Basic lesions that defines a disease process

[edit] Macule / Patch

• Macule: Circumcised, flat (non-palpable), discolored (hence you can see it)
  • Discoloration: brown, blue, red, hypopigmented
  • A tattoo is an artificial papule
• Large macules (~> 2cm) are called "patches"
  • Port-wine stain is an example of a macule
• 
• 
• 
• 
• 
• 

[edit] 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:
  • 
  • 
  • 
  • 
  • 
  • 
  • 

• Patches:
  • http://www.aad.org/Image%20Library/For%20the%20Public/Dermatology%20A%20-%20Z/herald-patch-woman.jpg?code=fcac6d1e-1f69-4953-9977-8db58c1f15a9
  • 
  • 
  • 
  • 

[edit] Nodule / Tumor

• Circumscribed, elevated, solid, 0.5-1 cm diameter
• Larger is a tumor

• Nodule:
  • 
  • 
  • 
  • 
  • 
  • 

• Tumor:
  • 
  • 
  • 
  • 

[edit] Wheal

• Firm, edematous plaque resulting because of infiltration of the dermis with fluid
  • Example is urticaria (hives) or a TB test
• Wheals are transient, may only last hours
• 
• 
• 
• http://itsmysocalledlife.files.wordpress.com/2009/02/190px-urtikaria_fuss.jpg%3Fw%3D190%26h%3D143

[edit] Pustule

• Circumscribed collection of leukocytes and free fluid, varies in size
• 
• 
• 
• 
• 
• 
• 
• 

[edit] Vesicle / Bulla

• Circumscribed collection of free fluid up to 0.5 cm diameter
  • In contrast to a pustule, contents are clear
  • Varicella zoster makes vesicles
• Bulla is over 0.5 cm diamter
  • Look differently depending on where the fluid resides: under the stratum corneum or under the whole epidermis

• Vesicles:
  • 
  • 

• Bullae:
  • 
  • 
  • 

[edit] Secondary Lesions

• Lesions that evolve from pt interaction with a disease process: scratching, picking, et cetera

[edit] Scales

• Excess dead epidermal cells that are produced by abnormal keratinization and shedding
• 
• 
• 
• 
• 

[edit] Crusts (scab) / Erosions

• Crust: collection of dried serum and cellular debris (a scab)
  • 
  • 

• Erosion: focal loss of epidermis
  • Any scratch that doesn't scar
  • Do not penetrate below the dermal-epidermal junction and thus do not scar
  • 
  • 
  • 

[edit] Escoriations

• Erosion caused by scratching
• Often linear

[edit] Ulcers

• A focal loss of epidermis and dermis
• Ulcers heal with scarring
• 
• 
• 
• 
• 
• 

[edit] Fissure

• Linear loss of epidermis and dermis with sharply defined, vertical walls
  • Chapped lips, for example
  • Think of corners of mouth
• 
• 
• 
• 
• 

[edit] Atrophy

• Depression in the skin from thinning of the epidermis or dermis
  • feels like cigarette paper
  • morvea: localized scleroderma
• http://mizzouderm.com/uploads/4/4/2/3/4423869/4212698_orig.jpg?214
• 
• 
• 

[edit] 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.
• To scar, one must get to the dermal papillary level, to the erector pili muscle.
• One year until the scar looks like it's final product
• 

[edit] Special Lesions

[edit] 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).
  • A type of acne.
• 
• 
• 
• 
• 

[edit] Lichenifcation

• Area of thickened epidermis induced by scratching.
  • These pts did it to themselves.
• Skin lines are accentuated so that the surface looks like a washboard
• How many times do you have to scratch yourself to induce lichenification: 200k scratches / rubs to get this response!
• 
• 

[edit] Burrow

• Narrow, elevated tortuous channel in the skin, created by a parasite
• Scabies most common
• 

[edit] Milia

• Small cysts under the skin; have walls containing epidermis
• Associated with scarring; when skin is scarring from injury, skin may form milia
• Porphyria can occur secondary to hepatitis C; makes skin of hands fragile, thus producing milia
• 
• 
• 
• 

[edit] Cyst

• Circumscribed with wall and lumen; may contain solid matter or fluid
  • A larger milia
• 
• 
• 
• 
• 
• 

[edit] Telangiectasia

• Dilated superficial blood vessels
  • Can indicate liver disease
• Also called spider angiomas is a form of telangiectasias with a lesion
• 
• 
• 
• 
• http://www.nytimes.com/imagepages/2007/08/01/health/adam/2998Telangiectasialegs.html

[edit] Petechiae / Purpura

• Petechiae: circumscribed deposit of blood, < 0.5 cm diameter
• Purpura: circumscribed deposit of blood, > 0.5 cm diameter

• Petechiae
  • 
  • 
  • 
  • 

• Purpura:
  • 
  • 
  • 
  • 

[edit] Examples

• Vitiligo: white macule at the nasal bridge, right edge of the nose, and inferior medial border of the right eye
• Port-wine stain: red macule across the distributuion of trigeminal V2
• Lichen planus: collection of papules forming a plaque on the right hand and wrist, linear in distribution
• Deep hemangioma: 2 cm tumor at the lateral, inferior border of the left eye, lacks ulceration, telangeictasia, or eruption