patho ch 40 & 41 skin disorders

acute skin condition

bacterial or fungal infection, contact w/ offending organism or allergen, medications; possible transition to chronic; life-threatening inflammatory disorders

chronic skin conditions

long term, may or may not resolve, viral infection

concepts related to acute skin disorders

pain from damage to first layer of skin, impaired tissue integrity leads to immune response, immune response from allergy & inflammation can lead to lack of tissue integrity, alterations in tissue perfusion can lead to damage or necrosis

cellulitis

Diffuse painful inflammation of skin and subcutaneous layers induced by a bacterial infection that enters through a break in the skin (cut, scrape, burn, or surgical incision, or bug bite); adult population

clinical manifestations of cellulitis

painful, red, swollen area of skin, hot & tender to touch, fever & chills, vesicles, bullae, plaques (w/ staphylococcus), tachycardia, HTN, confusion, headache, lymphadenitis, lymphangitis

impetigo

Superficial acute, highly contagious skin infection

etiology & pathogenesis of impetigo

bacterial colonization facilitated by high temperature, humidity, preexisting skin disorders, young age (ages 2-5), recent antibiotic treatment

furnucle

Extension of folliculitis or bacterial infection of sebaceous gland. spreads down hair shaft through follicle and into dermis

carbuncle

Cluster of infected hair follicles that coalesces to form lesion filled with pus, dead tissue, fluid

candidiasis

fungal infection skin or mucous membranes with any species of Candida; usually secondary condition

most common species causing candidiasis

C. albicans

commonly affected areas of candidiasis

mouth, throat, lungs, vagina, folds of skin, bowel

etiology & pathogenesis of candidiasis

Candida normal in skin and mucous membranes but warmth, moisture, breaks in epidermis can cause infection; life threatening if in bloodstream

clinical manifestations of candidiasis

thrush (white covering of tongue, mouth, throat, vaginal yeast infection (itching, foul odor, white discharge), balanitis (flattened pustules, edema, burning, tenderness), diaper rash (dark red patches in skin folds, fluid filled spots)

tinea

Contagious, superficial fungal infection (dermatophytoses) caused by different types of fungus

tinea pedis

athlete's foot, which affects the feet with symptoms like itching, scaling, and blisters between the toes

tinea cruris

jock itch, a rash in the groin area

tinea capitis

Ringworm of the scalp. Cause itchy, red patches and hair loss

tinea corporis

Ringworm on the body, appearing as a ring-shaped rash

tinea versicolor

Discolored, scaly, and dry patches on the skin

necrotizing fasciitis

Rapidly spreading infection caused by aerobic and anaerobic bacteria; “flesh eating disorder”

etiology & pathogenesis of necrotizing fasciitis

Starts from contagious ulcer, wound, untreated skin infection, complication of surgery, abscess, occlusion of small subcutaneous vessels, tissue ischemia, infarction, necrosis

stevens-johnson syndrome (SJS)

rare disorder of skin and mucous membranes; cell death causes epidermis to separate from dermis

etiology of SJS

200+ medications, infectious causes, delayed hypersensitive reaction

clinical manifestations of SJS

flulike symptoms, symmetric burning rash, red/purple target lesions

toxic epidermal necrolysis (TEN)

inflammation of skin caused by poison

TEN w/ spots

Widespread with detachment of epidermis, erosion (more than 30% of body surface area)

TEN w/o spots

Widespread with erythema, no lesions (more than 10% of body surface area)

etiology of TEN

Reactions to drugs, bacterial infection, malignancy, graft-versus-host disease, vaccinations

clinical manifestations of TEN

flulike symptoms, rash, large blisters in center rash, ruptures, skin peels off

Examples of common causative organisms of chronic viral skin infections

HSV, varicella-zoster, human papillomavirus

herpes labialis

libs, cold sores; most common HSV-1 infection

herpetic keratitis

eye

herpetic whitlow

digits or hands

herpes gladiatorum

torso of wrestlers

herpetic sycosis

beard follicles

HSV-1

usually contracted during childhood, recurrences persist into old age

HSV-2

Causes most sexually-transmitted anogenital herpes—lesions on genitals, perineum, or anus, likely to be contracted via sexual contact, 5th most common US STI, may cause cold sores

HSV etiology & pathogenesis

virus enters skin/mucous membrane via tear→sensory root ganglion→becomes dormant but permanent resident inside ganglion→cell mediated immune system triggered→viral activation→virus travels to skin innervated by neuron→dermal & epidermal cells→viral replication causes recurrent rash outbreak

clinical manifestations of HSV

may be asymptomatic or mild fever, usually begins w/ prodrome (fever/flulike symptoms), red swollen area of skin/mucous membrane develops, eruption of painful vesicles, regional lymph nodes swell, lesions open & form painful ulcers that crust & begin healing, primary genital herpes (may cause dysuria/urinary retention)

herpes zoster (shingles)

chronic viral skin condition affecting about 1 mil people

what causes shingles & chickenpox

varicella zoster virus (VZV) (member of herpesvirus family)

first VZV infection

causes chickenpox: each lesion contains viral particles which travel to other structures (sensory dorsal-root ganglia or CN) and become dormant for life

herpes zoster cell mediated immunity

prevents virus reactivation in the form of HZ but decreases w/ age increasing risk of VZV & HZ reactivation

potential complications of herpes zoster

postherpetic neuralgia, TIA & stroke, encephalitis & aseptic meningitis, chronic eye disorders & renal necrosis, bacterial superinfection of lesions, cranial/peripheral nerve palsies, pneumonitis, hepatitis

herpes zoster diagnosis

hx & physical exam (usually sufficient after rash appears, recurrent rashes may require lab testing (direct immunoflourescent assay or PCR assay)

cause of warts

various types of human papillomavirus (HPV)

sites of wart occurence

Anywhere on skin or mucous membranes

wart malignancy

most HPV lesions are benign but some are linked to dysplasia & cancer

genital HPV

most frequently occurring STI in US

pathogenesis of warts

HPV enters skin via small openings & infects epidermal basal layer, viral replication occur in cell nuclei, HPV causes nuclear atypia (structural cell abnormality) which triggers epidermal cell changes (replication & hyperproliferation of keratinocytes)→wart develops

Most important risk factor for certain chronic skin diseases

family diseases

chronic skin disorders w/ genetic component

atopic dermatitis, psoriasis, hidradenitis suppurativa

eczema

general term describing inflammatory skin disorders, including atopic dermatitis

most severe form of eczema

atopic dermatitis

atopic dermatitis (AD)

Chronic, recurring, itchy, inflammatory disorder associated with increased serum IgE; affected individuals often have other atopic disorders; mostly affects children but may persist into adulthood

AD & susceptibility to infection

dysfunctional epidermal barrier

clinical manifestations of AD

Exacerbation and remission of dry, itchy, red skin, begins in infancy, constant pruritus (itching) (precedes eczematous rash), skin excoriations & lichenification, negative impact on overall quality of life

etiology of psoriasis

immune-mediated disease, genetic & environmental causation

pathogenesis of psoriasis

hyperproliferation of keratinocytes, decreased epidermal cell turnover rate, inflammation, thickening of dermis & epidermis

manifestations of psoriasis

plaque psoriasis—skin lesions usually round or oval, well-demarcated plaques

etiology of hidradenitis suppurativa

genetic, immunologic, hormonal, environmental factors

pathogenesis of hidradenitis suppurativa

occlusion of hair follicle via infundibular hyperkeratosis, hyperplasia of follicular epithelium, collection of cellular waste, cyst forms in apocrine sweat gland adjacent to hair follicle, nodule opens beneath skin &  spreads laterally, may lead to abscess & sinus tract formation, keloid-like scarring may occur

manifestations of hidradenitis suppurativa

painful nodules, abscesses, sinus tract formations, lesions develop in skin fold areas