CHPT 8-Skin Disorders canvas ppt

Functions of the Skin

• Acts as first line of defense when unbroken.

• Prevents excessive fluid loss.

• Controls body temperature through:

  • Cutaneous vasodilation

  • Secretion and evaporation of sweat

• Active in sensory perception.

• Important defense against environmental hazards.

• Synthesizes vitamin D on exposure to small amounts of ultraviolet light.

Review of Normal Skin

• Layers of the skin:

  • Epidermis—avascular (has 5 layers)

  • Dermis

  • Subcutaneous tissue (hypodermis)

Layers of the Epidermis

• Stratum basale

  • Mitotic activity

• Stratum spinosum

  • Cells connected by desmosomes

  • Protein synthesis

• Stratum granulosum

  • Keratin formation begins

• Stratum lucidum

  • Clear layer, keratinocytes degenerate here

  • Has Eleidin which later transforms to Keratin

• Stratum corneum

  • Waterproofing barrier

Skin Cells

• Keratin

  • Waterproofing of the skin

• Melanin

  • Skin pigment—determines skin color

  • Production depends on multiple genes and environment

• Albinism

  • Lack of melatonin production

• Vitiligo

  • Small areas of hypopigmentation

• Melasma

  • Patches of darker skin

Dermis

• Connective tissue

  • Contains elastic and collagen fibers

  • Flexibility and strength of the skin

• Contains nerves and blood vessels

  • Includes sensory receptors for:

    • Pressure

    • Touch

    • Pain

    • Heat

    • Cold

Appendages of the Skin

• Nails

• Hair follicles

  • Stratum basale—hair-producing

  • Arrector pili muscle associated with hair follicle

• Sebaceous glands

  • Produce sebum

    • Secretion increases at puberty—influence of sex hormones

• Sweat glands

  • Eccrine—all over body

  • Apocrine

    • Axillae, scalp, face, external genitalia

Hypodermis

• Beneath dermis

  • Connective tissue

  • Fat cells

  • Macrophages

  • Fibroblasts

  • Larger blood vessels

  • Nerves

Resident (Normal) Flora of the Skin

• Mixed flora—components differ in various areas of the body.

• Microbes also reside under the fingernails, in hair follicles, and in glands.

• Opportunistic infections may occur because of injury or other inflammatory lesion.

• Infection may spread systemically from skin lesions.

Skin Lesions

• The physical appearance of the lesion is necessary to make a diagnosis.

• Skin lesions may be caused by:

  • Systemic disorders, e.g. Liver disease

  • Systemic infections, e.g. Chickenpox

  • Allergies to ingested food or drugs

  • Localized factors, e.g. exposure to toxins

• Types of lesions

  • Location

  • Length of time lesion has been present

  • Changes occurring over time

  • Physical appearance

    • Color

    • Elevation

    • Texture

    • Type of exudate

  • Presence of pain or pruritus (itching)

  • Review Table 8-1

Common Skin Lesions

• Macule: flat, circumscribed

• Papule: small, solid elevation

• Nodule: firm, raised, deep

• Pustule: raised, often with a "head," filled with exudate or "pus"

• Vesicle or blister: thin wall, raised, fluid filled

• Ulcer: cavity in tissue

• Plaque: Slightly elevated, flat, "scale"-like lesion

• Fissure: crack in tissue

Pruritus

• Associated with:

  • Allergic responses

  • Chemical irritation caused by insect bites

  • Infestations by parasites (e.g., scabies)

• Mechanism not totally understood

  • Release of histamine in a hypersensitivity response causes marked pruritus

  • Infection may result from breaking the skin barrier caused by scratching

Contact Dermatitis (Type IV)

• Exposure to an allergen

  • Metals, cosmetics, soaps, chemicals, plants

  • Sensitization occurs on first exposure.

  • Pruritic rash develops at site a few hours after exposure.

• Direct chemical or mechanical irritation

  • Does not involve immune response

  • Is inflammatory because of direct exposure

    • Removal of irritant

    • Reduction of inflammation with topical glucocorticoids

Pathophysiology of Contact Dermatitis

• Sensitization occurs on first exposure

• Subsequent exposure results in manifestations, i.e. pruritic rash

• Location of lesions is clue to identity of the allergen, i.e. poison ivy

• Signs and Symptoms:

  • Pruritic area

  • Erythematous area

  • Edematous area

  • Area often covered with small vesicles

• Chemical Irritation Manifestation

  • Edematous area

  • Erythematous area

  • May be pruritic or painful

Uticaria

• Pathophysiology:

  • Result of type I hypersensitivity

    • Ingestion of substances

      • Examples: shellfish, drugs, certain fruits

• Signs and Symptoms:

  • Eruption of hard, raised, erythematous lesion

  • Lesions are highly pruritic

  • Found:

    • Skin

    • May be scattered all over body

    • Occasionally in pharyngeal mucosa

      • Airway obstruction

Atopic Dermatitis (Eczema)

• Atopic—inherited tendency (Type I)

• Common problem in infancy

  • Rash is erythematous, with serous exudate.

  • Commonly occurs on face, chest, and shoulders

• In adults, rash is dry, scaly, and pruritic, often on flexor surfaces.

• Pathophysiology

  • Chronic inflammation results from response to allergens.

    • Eosinophilia and increased serum IgE levels

  • Affected areas become sensitive to irritants:

    • Soaps

    • Certain fabrics

    • Temperature changes

  • Potential complication

    • Secondary infections due to scratching

Psoriasis

• Chronic inflammatory skin disorder

• Autoimmune disease

• Affects 1 – 3% of the population

• Believed to be genetic in origin

• Pathophysiology:

  • Onset usually in the teenage years

  • Marked by remission and exacerbations

  • Cases vary in severity

  • Results from abnormal T cell activation.

    • Excessive proliferation of keratinocytes

    • Cellular proliferation is greatly increased leading to thickening of the dermis and epidermis

    • Shedding occurs in one day rather than two week intervals

• Signs and Symptoms

  • Red patches of skin covered with silvery scales

  • Small scaling spots (commonly seen in children)

  • Dry, cracked skin that may bleed

  • Itching, burning or soreness

  • Thickened, pitted or ridged nails

  • Swollen and stiff joints

  • (Can affect multiple organs)

Pemphigus

• Autoimmune disorder

• Mainly two forms

  • Pemphigus vulgaris (mucosal)

  • Pemphigus foliaceous (Skin)

• Severity varies among individuals

• Autoantibodies disrupt cohesion between epidermal cells.

  • Causes blisters (bullae) to form

  • Skin sheds, leaving area painful and open to secondary infection.

  • May be life-threatening if extensive (e.g., Stevens-Johnson syndrome)

• Signs and Symptoms

  • Blisters in mouth

  • Blisters spreading to the skin

  • Blisters are painful but not pruritic

  • Breathing difficulty due to swollen mouth and throat

Scleroderma

• May occur as skin disorder

• May be systemic and affect viscera

• Primary cause unknown

• Pathophysiology:

  • Increased collagen deposition

  • Inflammation and fibrosis with decreased capillary networks

  • May cause renal failure, intestinal obstruction, respiratory failure caused by distortion of tissues

• Signs and Symptoms:

  • Hard, shiny, tight, immovable areas of skin

  • Fingertips narrowed and shortened

    • Raynaud's phenomenon may be present (lack of blood flow to toes and fingers)

  • Facial expression is lost

    • Skin tightens, movement of the mouth and eyes may be impaired

  • The cutaneous form may also affect the microcirculation of various organs, eventually causing renal failure, intestinal obstruction, or respiratory failure due to pulmonary hypertension.

Dupuytrens Contracture

• Pathophysiology

  • Progressive hand deformity

  • Cause is unknown

  • Knots of tissue under skin of palms

  • Fingers eventually pulled into bent position

Skin Infections

• May be caused by bacteria, viruses, fungi, other types of microbes, parasites

• Caused by opportunistic microbes

• Minor abrasions or cuts

• Serious infections may develop.

• Causative organism needs to be identified for appropriate treatment

• Bacterial Infections:

  • Primary

    • Often caused by resident flora

  • Secondary

    • Developing in wounds or pruritic lesions

Cellulitis (erysipelas)

• Infection of the dermis and subcutaneous tissue

• Usually secondary to an injury

• Causative organism

  • Usually Staphylococcus aureus

  • Sometimes Streptococcus

  • Frequently in lower trunks and legs

    • Especially in individuals with restricted circulation in the extremities; also in immunocompromised individuals

  • Area becomes red, swollen, and painful

  • Red streaks may develop, running along lymph vessels proximal to infected area

• Signs and Symptoms

  • Reddened area

  • Edematous (swollen)

  • Pain

  • Red streaks along the lymph vessels proximal to the infected area

Furuncules (boils)

• Usually caused by S. aureus

• Begins at hair follicles

• Face, neck, back

• Frequently drains large amounts of purulent exudate

• Autoinoculation

  • Squeezing boils can result in spread of infection to other areas of the skin.

Impetigo

• Common infection in infants and children

  • May also occur in adults

  • S. aureus—highly contagious in neonates

• Lesions commonly on face

• Transmission may occur through close physical contact or through fomites

• Pruritus common

  • Leads to scratching and further spread of infection

• Signs and Symptoms

  • Small red vesicles, which rapidly enlarge

  • Vesicles rupture forming yellowish-brown crusty masses

  • Additional vesicles develop around the primary site by autoinoculation with hands, towels, or clothes

  • Pruritus is common, leading to scratching and further spread of infection

Acute Necrotizing Fasciitis

• Fascia is the connective tissue that surrounds the blood vessels/nerve and muscles

• Mixture of aerobic and anaerobic bacteria usually at site of infection

• Severe inflammation and tissue necrosis

  • Usually caused by virulent strain of gram-positive, group A beta-hemolytic Streptococcus

  • Bacteria secrete toxins that break down fascia and connective tissue, causing massive tissue destruction.

• Often a history of minor trauma or infection in the skin and subcutaneous tissue of an extremity

• Signs and Symptoms

  • Local S/S:

    • Infected area appears markedly inflamed

    • Very painful

    • Infected area rapidly increases in size

    • Dermal gangrene is apparent

  • Systemic S/S:

    • Fever

    • Tachycardia

    • Hypotension

    • Mental confusion and disorientation

    • Possible organ failure

Leprosy (Hansen’s Disease)

• Caused by Mycobacterium leprae

• Chronic disease classified into three major types

• Clinical signs and symptoms vary.

  • Generally affects skin, mucous membranes, and peripheral nerves

  • Damage can lead to loss of limbs.

• Mechanism of pathogenicity largely unknown

Herpes Simplex

• Herpes simplex type 1 (HSV-1)

  • Most common cause of cold sores or fever blisters

• Herpes simplex type 2 (HSV-2)—genital herpes

• Both types of HSV cause similar effects.

• Primary infection may be asymptomatic

  • Virus remains latent in sensory nerve ganglia.

• Recurrence may be triggered by:

  • Common cold, sun exposure, stress

• Spread by direct contact with fluid from lesion

• Spread of infection to others possible prior to appearance of lesions

• Potential complication:

  • Spread of virus to eye

    • Keratitis

  • Herpetic whitlow

    • Painful infection of the fingers

Verrucae (Warts)

• Human papillomavirus (HPV) types 1 to 4

  • Frequently develop in children and young adults

• Plantar warts are common.

• Spreads by viral shedding of the skin surface

• May resolve spontaneously with time

• Genital warts (HPV types 6 and 11)

Fungal Infections (Mycoses)

• Most are superficial

  • Candida infection is associated with diabetes.

  • May spread systemically in immunocompromised individuals

Tinea

• Tinea capitis

  • Infection of the scalp

  • Common in school-age children

  • Erythema may be apparent.

• Tinea corporis

  • Infection of the body, particularly of nonhairy parts

  • Round lesion with clear center (ringworm)

  • Pruritus may be present.

• Tinea pedis

  • Athlete’s foot—involves the feet, particularly the toes

  • Associated with swimming pools and gymnasiums

  • May be part of normal flora that becomes opportunistic

  • Secondary bacterial infection may occur

• Tinea unguium

  • Infection of the nails, particularly the toenails

    • Nails turn white, then brown.

    • Nail thickens and cracks.

    • Infection tends to spread to other nails.

Other Infections

• Scabies

  • Invasion by mite Sarcoptes scabiei

  • Female burrows into epidermis

    • Lays eggs over a period of several weeks

    • Male dies after fertilizing the female

    • Female dies after laying the eggs.

  • Larvae migrate to skin surface.

    • Burrow into skin in search of nutrients

    • Intensely pruritic!

  • Larvae mature and cycle is repeated

  • Burrows appear on skin as tiny, light brown lines.

• Pediculosis (lice)

  • Pediculus humanus corporis—body louse

  • Pediculus humanus capitis—head louse

  • Pediculus humanus pubis—pubic louse

  • Female lice lay eggs on hair shafts.

  • After hatching, louse bites human host, sucking blood for production of ova

  • Excoriations result from scratching.

Skin Tumors: Keratoses

• Benign lesions usually associated with aging or skin damage.

• Seborrheic keratoses

  • Proliferation of basal cells

    • Lead to oval elevation

    • May be smooth or rough

• Actinic keratoses

  • On skin exposed to ultraviolet radiation

  • Commonly in fair-skinned persons

  • Lesion appears as pigmented, scaly patch

Warning Signs of Skin Cancer

• A sore that does not heal

• A change in shape, size, color, or texture of a lesion, especially an expanding, irregular circumference or surface

• New moles or odd-shaped lesions that develop

• A skin lesion that bleeds repeatedly, oozes fluid, or itches

Guidelines to Reduce Risk of Skin Cancers

• Reducing sun exposure at midday and early afternoon

• Covering up with clothing

  • Remaining in shade

  • Wearing broad-brimmed hats to protect face and neck

• Applying sunscreen or sunblock

• Protecting infants and children from exposure and sun damage to skin

Squamous Cell Carcinoma

• Painless, malignant tumor of the epidermis

• Lesions most commonly found on exposed areas of the skin but also in oral cavity

  • Face and neck

  • Base of tongue

• Excellent prognosis when lesion is removed within reasonable time

• Invasive type arises from premalignant condition.

Malignant Melanoma

• Highly metastatic form of skin cancer

• Develops in melanocytes

  • From a nevus (mole)

• Often appear as multicolored lesion with irregular border

• Grow quickly

• Change in shape, color, size, texture

• May bleed

The ABCD of Melanoma

• Melanoma is suspected in any nevus that shows:

  • Change in appearance

  • Change in border

  • Change in color

  • Increase in diameter

Kaposi’s Sarcoma

• Occurs in those with AIDS and other immunodeficiencies

• May affect viscera as well as skin

• Malignant cells arise from endothelium in small blood vessels

  • Purplish macules

  • Nonpruritic, nonpainful

• In immunocompromised patients, lesions develop rapidly over upper body.

Functions of the Skin

• Acts as first line of defense when unbroken, preventing pathogen entry and physical damage.

• Prevents excessive fluid loss, maintaining hydration and electrolyte balance.

• Controls body temperature through:

  • Cutaneous vasodilation: Increases blood flow to the skin surface, dissipating heat.

  • Secretion and evaporation of sweat: Cools the body as sweat evaporates.

• Active in sensory perception:

  • Contains receptors for touch, pressure, pain, and temperature.

• Important defense against environmental hazards:

  • UV radiation, pollutants, and mechanical irritants.

• Synthesizes vitamin D on exposure to small amounts of ultraviolet light:

  • Essential for calcium absorption and bone health.

Review of Normal Skin

• Layers of the skin:

  • Epidermis—avascular (has 5 layers):

    • Outermost layer, provides a waterproof barrier and creates our skin tone.

    • Relies on the dermis for nutrient supply.

  • Dermis:

    • Contains blood vessels, nerves, hair follicles, and glands.

    • Provides structural support and elasticity.

  • Subcutaneous tissue (hypodermis):

    • Adipose tissue for insulation and cushioning.

    • Contains larger blood vessels and nerves.

Layers of the Epidermis

• Stratum basale:

  • Mitotic activity: Cell division to replenish skin cells.

  • Contains melanocytes that produce melanin.

• Stratum spinosum:

  • Cells connected by desmosomes: Provides strength and flexibility.

  • Protein synthesis: Production of keratin and other proteins.

• Stratum granulosum:

  • Keratin formation begins: Cells accumulate granules containing keratin.

  • Cells begin to die as they move away from nutrient source.

• Stratum lucidum:

  • Clear layer, keratinocytes degenerate here

  • Has Eleidin which later transforms to Keratin

• Stratum corneum:

  • Waterproofing barrier: Dead, flattened cells filled with keratin.

  • Protects against abrasion and penetration.

Skin Cells

• Keratin:

  • Waterproofing of the skin: Provides a protective barrier.

  • Produced by keratinocytes.

• Melanin:

  • Skin pigment—determines skin color

  • Production depends on multiple genes and environment

  • Protects against UV radiation.

• Albinism:

  • Lack of melatonin production

  • Genetic condition resulting in absence of pigment in skin, hair, and eyes.

• Vitiligo:

  • Small areas of hypopigmentation

  • Autoimmune condition causing loss of melanocytes.

• Melasma:

  • Patches of darker skin

  • Often associated with hormonal changes, such as pregnancy.

Dermis

• Connective tissue:

  • Contains elastic and collagen fibers

  • Flexibility and strength of the skin

  • Supports epidermis and provides structure.

• Contains nerves and blood vessels:

  • Includes sensory receptors for:

    • Pressure

    • Touch

    • Pain

    • Heat

    • Cold

Appendages of the Skin

• Nails:

  • Protective keratinized structures on fingers and toes.

• Hair follicles:

  • Stratum basale—hair-producing

  • Arrector pili muscle associated with hair follicle

  • Hair provides insulation and protection.

• Sebaceous glands:

  • Produce sebum

  • Secretion increases at puberty—influence of sex hormones

  • Lubricates skin and hair.

• Sweat glands:

  • Eccrine—all over body

    • Regulates body temperature through perspiration.

  • Apocrine:

    • Axillae, scalp, face, external genitalia

    • Produce thicker sweat with pheromones.

Hypodermis

• Beneath dermis

• Connective tissue:

  • Fat cells: Provide insulation and energy storage.

  • Macrophages: Immune cells that engulf pathogens and debris.

  • Fibroblasts: Produce collagen and elastin.

  • Larger blood vessels

  • Nerves

Resident (Normal) Flora of the Skin

• Mixed flora—components differ in various areas of the body.

  • Includes bacteria, fungi, and viruses.

• Microbes also reside under the fingernails, in hair follicles, and in glands.

  • Serve as a reservoir for potential infections.

• Opportunistic infections may occur because of injury or other inflammatory lesion.

  • Disruption of skin barrier allows entry of pathogens.

• Infection may spread systemically from skin lesions.

  • Bacteria can enter the bloodstream and cause widespread infection.

Skin Lesions

• The physical appearance of the lesion is necessary to make a diagnosis.

  • Distribution, size, shape, color, and texture are important.

• Skin lesions may be caused by:

  • Systemic disorders, e.g. Liver disease

    • Manifestations of internal diseases on the skin.

  • Systemic infections, e.g. Chickenpox

    • Viral or bacterial infections causing skin eruptions.

  • Allergies to ingested food or drugs

    • Immune responses triggered by allergens.

  • Localized factors, e.g. exposure to toxins

    • Irritants or chemicals causing local skin reactions.

• Types of lesions

  • Location

  • Length of time lesion has been present

  • Changes occurring over time

  • Physical appearance

    • Color

    • Elevation

    • Texture

    • Type of exudate

  • Presence of pain or pruritus (itching)

  • Review Table 8-1

Common Skin Lesions

• Macule: flat, circumscribed

• Papule: small, solid elevation

• Nodule: firm, raised, deep

• Pustule: raised, often with a "head," filled with exudate or "pus"

• Vesicle or blister: thin wall, raised, fluid filled

• Ulcer: cavity in tissue

• Plaque: Slightly elevated, flat, "scale"-like lesion

• Fissure: crack in tissue

Pruritus

• Associated with:

  • Allergic responses

    • Histamine release causes itching.

  • Chemical irritation caused by insect bites

    • Irritants trigger inflammatory response.

  • Infestations by parasites (e.g., scabies)

    • Mites burrowing into skin cause intense itching.

• Mechanism not totally understood

  • Release of histamine in a hypersensitivity response causes marked pruritus

  • Infection may result from breaking the skin barrier caused by scratching

    • Secondary bacterial infections common.

Contact Dermatitis (Type IV)

• Exposure to an allergen

  • Metals, cosmetics, soaps, chemicals, plants

  • Sensitization occurs on first exposure.

  • Pruritic rash develops at site a few hours after exposure.

• Direct chemical or mechanical irritation

  • Does not involve immune response

  • Is inflammatory because of direct exposure

    • Removal of irritant

    • Reduction of inflammation with topical glucocorticoids

Pathophysiology of Contact Dermatitis

• Sensitization occurs on first exposure

• Subsequent exposure results in manifestations, i.e. pruritic rash

• Location of lesions is clue to identity of the allergen, i.e. poison ivy

• Signs and Symptoms:

  • Pruritic area

  • Erythematous area

  • Edematous area

  • Area often covered with small vesicles

• Chemical Irritation Manifestation

  • Edematous area

  • Erythematous area

  • May be pruritic or painful

Uticaria

• Pathophysiology:

  • Result of type I hypersensitivity

  • Ingestion of substances

  • Examples: shellfish, drugs, certain fruits

• Signs and Symptoms:

  • Eruption of hard, raised, erythematous lesion

  • Lesions are highly pruritic

  • Found:

    • Skin

    • May be scattered all over body

    • Occasionally in pharyngeal mucosa

      • Airway obstruction

Atopic Dermatitis (Eczema)

• Atopic—inherited tendency (Type I)

• Common problem in infancy

  • Rash is erythematous, with serous exudate.

  • Commonly occurs on face, chest, and shoulders

• In adults, rash is dry, scaly, and pruritic, often on flexor surfaces.

• Pathophysiology

  • Chronic inflammation results from response to allergens.

    • Eosinophilia and increased serum IgE levels

  • Affected areas become sensitive to irritants:

    • Soaps

    • Certain fabrics

    • Temperature changes

  • Potential complication

    • Secondary infections due to scratching

Psoriasis

• Chronic inflammatory skin disorder

• Autoimmune disease

• Affects 1 – 3% of the population

• Believed to be genetic in origin

• Pathophysiology:

  • Onset usually in the teenage years

  • Marked by remission and exacerbations

  • Cases vary in severity

  • Results from abnormal T cell activation.

    • Excessive proliferation of keratinocytes

    • Cellular proliferation is greatly increased leading to thickening of the dermis and epidermis

    • Shedding occurs in one day rather than two week intervals

• Signs and Symptoms

  • Red patches of skin covered with silvery scales

  • Small scaling spots (commonly seen in children)

  • Dry, cracked skin that may bleed

  • Itching, burning or soreness

  • Thickened, pitted or ridged nails

  • Swollen and stiff joints

  • (Can affect multiple organs)

Pemphigus

• Autoimmune disorder

• Mainly two forms

  • Pemphigus vulgaris (mucosal)

  • Pemphigus foliaceous (Skin)

• Severity varies among individuals

• Autoantibodies disrupt cohesion between epidermal cells.

  • Causes blisters (bullae) to form

  • Skin sheds, leaving area painful and open to secondary infection.

  • May be life-threatening if extensive (e.g., Stevens-Johnson syndrome)

• Signs and Symptoms

  • Blisters in mouth

  • Blisters spreading to the skin

  • Blisters are painful but not pruritic

  • Breathing difficulty due to swollen mouth and throat

Scleroderma

• May occur as skin disorder

• May be systemic and affect viscera

• Primary cause unknown

• Pathophysiology:

  • Increased collagen deposition

  • Inflammation and fibrosis with decreased capillary networks

  • May cause renal failure, intestinal obstruction, respiratory failure caused by distortion of tissues

• Signs and Symptoms:

  • Hard, shiny, tight, immovable areas of skin

  • Fingertips narrowed and shortened

    • Raynaud's phenomenon may be present (lack of blood flow to toes and fingers)

  • Facial expression is lost

    • Skin tightens, movement of the mouth and eyes may be impaired

  • The cutaneous form may also affect the microcirculation of various organs, eventually causing renal failure, intestinal obstruction, or respiratory failure due to pulmonary hypertension.

Dupuytrens Contracture

• Pathophysiology

  • Progressive hand deformity

  • Cause is unknown

  • Knots of tissue under skin of palms

  • Fingers eventually pulled into bent position

Skin Infections

• May be caused by bacteria, viruses, fungi, other types of microbes, parasites

• Caused by opportunistic microbes

• Minor abrasions or cuts

• Serious infections may develop.

• Causative organism needs to be identified for appropriate treatment

• Bacterial Infections:

  • Primary

    • Often caused by resident flora

  • Secondary

    • Developing in wounds or pruritic lesions

Cellulitis (erysipelas)

• Infection of the dermis and subcutaneous tissue

• Usually secondary to an injury

• Causative organism

  • Usually Staphylococcus aureus

  • Sometimes Streptococcus

  • Frequently in lower trunks and legs

    • Especially in individuals with restricted circulation in the extremities; also in immunocompromised individuals

  • Area becomes red, swollen, and painful

  • Red streaks may develop, running along lymph vessels proximal to infected area

• Signs and Symptoms

  • Reddened area

  • Edematous (swollen)

  • Pain

  • Red streaks along the lymph vessels proximal to the infected area

Furuncules (boils)

• Usually caused by S. aureus

• Begins at hair follicles

• Face, neck, back

• Frequently drains large amounts of purulent exudate

• Autoinoculation

  • Squeezing boils can result in spread of infection to other areas of the skin.

Impetigo

• Common infection in infants and children

  • May also occur in adults

  • S. aureus—highly contagious in neonates

• Lesions commonly on face

• Transmission may occur through close physical contact or through fomites

• Pruritus common

  • Leads to scratching and further spread of infection

• Signs and Symptoms

  • Small red vesicles, which rapidly enlarge

  • Vesicles rupture forming yellowish-brown crusty masses

  • Additional vesicles develop around the primary site by autoinoculation with hands, towels, or clothes

  • Pruritus is common, leading to scratching and further spread of infection

Acute Necrotizing Fasciitis

• Fascia is the connective tissue that surrounds the blood vessels/nerve and muscles

• Mixture of aerobic and anaerobic bacteria usually at site of infection

• Severe inflammation and tissue necrosis

  • Usually caused by virulent strain of gram-positive, group A beta-hemolytic Streptococcus

  • Bacteria secrete toxins that break down fascia and connective tissue, causing massive tissue destruction.

• Often a history of minor trauma or infection in the skin and subcutaneous tissue of an extremity

• Signs and Symptoms

  • Local S/S:

    • Infected area appears markedly inflamed

    • Very painful

    • Infected area rapidly increases in size

    • Dermal gangrene is apparent

  • Systemic S/S:

    • Fever

    • Tachycardia

    • Hypotension

    • Mental confusion and disorientation

    • Possible organ failure

Leprosy (Hansen’s Disease)

• Caused by Mycobacterium leprae

• Chronic disease classified into three major types

• Clinical signs and symptoms vary.

  • Generally affects skin, mucous membranes, and peripheral nerves

  • Damage can lead to loss of limbs.

• Mechanism of pathogenicity largely unknown

Herpes Simplex

• Herpes simplex type 1 (HSV-1)

  • Most common cause of cold sores or fever blisters

• Herpes simplex type 2 (HSV-2)—genital herpes

• Both types of HSV cause similar effects.

• Primary infection may be asymptomatic

  • Virus remains latent in sensory nerve ganglia.

• Recurrence may be triggered by:

  • Common cold, sun exposure, stress

• Spread by direct contact with fluid from lesion

• Spread of infection to others possible prior to appearance of lesions

• Potential complication:

  • Spread of virus to eye

    • Keratitis

  • Herpetic whitlow

    • Painful infection of the fingers

Verrucae (Warts)

• Human papillomavirus (HPV) types 1 to 4

  • Frequently develop in children and young adults

• Plantar warts are common.

• Spreads by viral shedding of the skin surface

• May resolve spontaneously with time

• Genital warts (HPV types 6 and 11)

Fungal Infections (Mycoses)

• Most are superficial

  • Candida infection is associated with diabetes.

  • May spread systemically in immunocompromised individuals

Tinea

• Tinea capitis

  • Infection of the scalp

  • Common in school-age children

  • Erythema may be apparent.

• Tinea corporis

  • Infection of the body, particularly of nonhairy parts

  • Round lesion with clear center (ringworm)

  • Pruritus may be present.

• Tinea pedis

  • Athlete’s foot—involves the feet, particularly the toes

  • Associated with swimming pools and gymnasiums

  • May be part of normal flora that becomes opportunistic

  • Secondary bacterial infection may occur

• Tinea unguium

  • Infection of the nails, particularly the toenails

    • Nails turn white, then brown.

    • Nail thickens and cracks.

    • Infection tends to spread to other nails.

Other Infections

• Scabies

  • Invasion by mite Sarcoptes scabiei

  • Female burrows into epidermis

    • Lays eggs over a period of several weeks

    • Male dies after fertilizing the female

    • Female dies after laying the eggs.

  • Larvae migrate to skin surface.

    • Burrow into skin in search of nutrients

    • Intensely pruritic!

  • Larvae mature and cycle is repeated

  • Burrows appear on skin as tiny, light brown lines.

• Pediculosis (lice)

  • Pediculus humanus corporis—body louse

  • Pediculus humanus capitis—head louse

  • Pediculus humanus pubis—pubic louse

  • Female lice lay eggs on hair shafts.

  • After hatching, louse bites human host, sucking blood for production of ova

  • Excoriations result from scratching.

Skin Tumors: Keratoses

• Benign lesions usually associated with aging or skin damage.

• Seborrheic keratoses

  • Proliferation of basal cells

  • Lead to oval elevation

    • May be smooth or rough

• Actinic keratoses

  • On skin exposed to ultraviolet radiation

  • Commonly in fair-skinned persons

  • Lesion appears as pigmented, scaly patch

Warning Signs of Skin Cancer

• A sore that does not heal

• A change in shape, size, color, or texture of a lesion, especially an expanding, irregular circumference or surface

• New moles or odd-shaped lesions that develop

• A skin lesion that bleeds repeatedly, oozes fluid, or itches

Guidelines to Reduce Risk of Skin Cancers

• Reducing sun exposure at midday and early afternoon

• Covering up with clothing

  • Remaining in shade

  • Wearing broad-brimmed hats to protect face and neck

• Applying sunscreen or sunblock

• Protecting infants and children from exposure and sun damage to skin

Squamous Cell Carcinoma

• Painless, malignant tumor of the epidermis

• Lesions most commonly found on exposed areas of the skin but also in oral cavity

  • Face and neck

  • Base of tongue

• Excellent prognosis when lesion is removed within reasonable time

• Invasive type arises from premalignant condition.

Malignant Melanoma

• Highly metastatic form of skin cancer

• Develops in melanocytes

  • From a nevus (mole)

• Often appear as multicolored lesion with irregular border

• Grow quickly

• Change in shape, color, size, texture

• May bleed

The ABCD of Melanoma

• Melanoma is suspected in any nevus that shows:

  • Change in appearance

  • Change in border

  • Change in color

  • Increase in diameter

Kaposi’s Sarcoma

• Occurs in those with AIDS and other immunodeficiencies

• May affect viscera as well as skin

• Malignant cells arise from endothelium in small blood vessels

  • Purplish macules

  • Nonpruritic, nonpainful

• In immunocompromised patients, lesions develop rapidly over upper body.