Skin infections and infestations Flashcards
Bacterial Diseases
Impetigo
How is it transmitted?
what are some predisposing factors?
- Most common superficial bacterial infection of children.
- Acquired by person-to-person contact
- Less commonly acquired through fomites
- Predisposing factors- high humidity, cutaneous carriage, poor hygiene
Streptococcal Non-Bullous Impetigo
(Impetigo Contagiosa)
Most commonly affects _____ of children
Primary lesion is a _______ yellow crust.
Associated with post-streptococcal __________.
- Most commonly affects face (children)
- Typically begins as single lesion → multiple
- Primary lesion- “honey-colored” yellow crust
- Mild lymphadenopathy- variably present
- Up to 5% of streptococcal impetigo associated with acute post-streptococcal glomerulonephritis**
Agent: Streptococcus pyogenes
Staphylococcal Non-bullous impetigo
Most commonly affects the ______.
Frequently a secondary lesion of ______.
What color is the primary lesion?
- Most commonly affects face
- Any age group
- Frequently a secondary lesion of superficial injury or dermatitis.
- Primary lesion- yellow to amber-colored crust with variable erythema.
Bullous Impetigo
Bullous Impetigo
Diagnosis and clinical presentation
-Culture and sensitivity of crust or fluid from intact bullae
Gramstain of crust or fluid from intact bullae (see photo that demonstrates characteristic short chains of gram-positive cocci typical of S. pyogenes amongst numerous neutrophils).
Skin biopsy (rarely done)
Cellulitis
There is an increased incidence is the ______.
•Increased susceptibility:
–Very young
–Elderly
–Immunocompromised
–Intravenous drug users
–Patients with chronic ulcers
- Post-surgical complication
- Increased incidence in summer
- Infections occur through skin breaks
What organism cause Cellulitis?
For Eryiseplas the causative agent is ________.
For cellulitis the cause agents can be ______, ______, _____.
For Eryiseplas ( a facial variant of cellulitis)
–Group A β-hemolytic streptococci (streptococcus pyogenes)
For Cellulitis:
–Group A β-hemolytic streptococci (streptococcus pyogenes).
–Staphylococcus aureus
–Haemophilus influenzae (in children)
–Less commonly other streptococci, Pneumococcus, Klebsiella, Yersinia, mixed flora
Erysipelas
Erysipelas (St. Anthony’s fire)
Most commonly confined to the face less commonly the extremities
Incubation period- 2 to 5 days
Variable systemic symptoms- fever, chills, and malaise
Primary lesion- sharply demarcated area of erythema (cliff-drop border) that demonstrates non-pitting edema (lesions are often painful)
Regional lymphadenopathy- strictly present
Rarely the overlying epidermis may demonstrate bullae, pustules or hemorrhagic necrosis
Cellulitis
Staphylococcal
Most commonly located on the extremities
Incubation period- 2 to 5 days
Primary lesion- ill-defined non-palpable or subtly palpable area of painful erythema fact is warm to the touch.
Older lesions may demonstrate variable hemorrhage
Lymphatic streaking commonly present
Regional lymphadenopathy frequently present
Patients may progress to septicemia
Cellulitis
Diagnosis
CBC may demonstrate ________.
•Clinical presentation
- CBC- may demonstrate leukocytosis
- Biopsy
–Consistent with- organisms difficult to find
–Culture- more sensitive and specific
•Culture and Gram stain of leading edge
–Occasionally used (often negative)
•Blood cultures- + in 10%
Cellulitis treatment
Fungi
They are eukaryotes that lack _______in contrast to plant kindom.
- Fungus = from Greek “sponge”
- Mushroom = from Latin “fungus”
- Eukaryotes, unlike bacteria and blue-green algae
- Separate from plant kingdom - lack chlorophyll
- Non-photosynthetic
- Most are saprophytes - eat dead stuff)
- Some are parasites.
- 90,000 known species (likely > 1.5 mil)
Dermatophytes
This fungi eat _______ on human surfaces.
-Infections acquired from humans, animals, fomites (e.g., hats) and soil
Tinea Capitis
Tenia capitis variant Kerion is charaterized by_______.
Infection of scalp hair by Tricophyton tonsurans
Kerion characterized by abscess formation.
Tenia Faciei
Tenia faciei- infection of the face
Variation–> Tinea barbae- infection limited to the beard
Tinea Corporis
Characterized by infecion of ______ skin.
Tinea corporis- infection of glabrous (non-hair bearing) skin
Majocchi’s granuloma- variant characterized by follicular pustules and granulomas
Tenia cruris
Refers to infection of the _______ region.
Causative fungus is_______
Epidermophyton floccosum- common cause of tinea cruris
Tenia Pedis
Trichophyton mentagrophytes- common cause of tinea pedis
Two-feet One hand syndrome
Tenia unquiuum (onychomycosis)- infection of the *nail
Diagnosis of fungus:
Oral candidiasis (thrush)
Angular cheilitis (perlèche)
Candida diaper dermatitis
Diagnosis of Candidiasis:
Tinea Versicolor
Epidemiology
Confined to what patients?
Causative agent?
What do they eat?
- Worldwide distribution
- More common in humid and warm climates
- Confined to **post-pubertal patients
***Malassezia furfur (Pityrosporum orbiculare)
•Food source- follicular lipids**
Tenia versicolor
What are the clinical features?
Primarily distributed to the ______.
- Distribution- primarily truncal
- Primary lesion- asymptomatic, tan-colored subtly scaly macule or patch
- Clinical variants
–**Hypopigmented variant
–**Folliculitis
Tenia Versicolor
Tenia versicolor
Diagnosis
Scabies
What is a symptom? Usually at what time?
- Distribution- symmetric- interdigital web space, flexural wrist, waist, axillae, genitalia and breast (soft skin distribution)
- Symptoms- pruritus (nocturnal accentuation)
- Primary lesions
–Erythematous papules
–***Erythematous burrows- variable scale
–Nodular lesions on genitalia
- Secondary lesions- excoriations, infection
- Norwegian scabies- immunocompromised and individuals with ↓sensory function
Scabies
Lice
•Epidemiology
–Worldwide infestations
–Body lice
•Most common in indigents
–Head lice- 12 million new cases per year
•Most common in children
–Crab lice
•Most common in homosexuals and young men
- Scalp louse- Pediculus humanus var. capitis
- Body louse- Pediculus humanus var. corporis
–> Pubic louse- Phthirus (Pthirus) pubis
Body Lice
- Lice and eggs- morphologically identical to scalp lice
- Location- found only on clothing
- Clinical findings truncal erythematous papules and macules
- Intense ***pruritus
- Secondary excoriation- common
Pubic Lice
•Distribution- primarily genital region
–Less commonly eyelashes, beard, axilla
- Symptoms- marked pruritus of genital area
- Nits similar to head and body lice
- Adults- six legs, crab-like, easily found attached to base of hair follicles
Lice treatment
