WEEK # - CHAPTER #: MAIN TOPIC
WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
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OUTLINE
I.
II.
III.
IV.
Skin Anatomy
A. Sensory Receptors in the Layers of the Skin
B. Types of Lesions
1. Primary Lesions
2. Secondary Lesions
Skin Disorders
A. Acne & Related Disorders
1. Acne Vulgaris
2. Acne Rosacea
3. Hidradenitis Suppurativa
B. Arthropods
1. Scabies
2. Pediculosis Capitis (Head Lice)
3. Pediculosis Pubis (Phthiriasis)
4. Insect Bites
C. Bacterial Diseases
1. Impetigo
2. Erysipelas
3. Folliculitis
D. Fungal Infections
1. Diagnosis of Fungal Infection
2. Tinea Infections
3. Treatment for Tinea
4. Candidiasis
E. Viral Diseases
1. Herpes Simplex
2. Varicella
3. Herpes Zoster
4. Measles (Rubeola)
5. Verruca (Warts)
F. Other Skin Diseases
1. Dermatitis (Eczema)
2. Cellulitis
Skin Examinations
A. History
B. Physical Assessment
C. Color
D. Moisture
E. Turgor
F. Integrity
Appendix
I. SKIN ANATOMY
A. SENSORY RECEPTORS IN THE LAYERS OF THE SKIN
SKIN RECEPTORS
LOCATION
FUNCTION
Free nerve endings
Epidermis, dermis
Pain & itch
Merkel’s discs
Stratum
spinosum
Light touch, 2-point
discrimination
Meissner’s corpuscle
Papillary dermis
Discriminative touch
Ruffini’s corpuscle
Papillary dermis
Warm
Krause’s end bulb
Papillary dermis
Cold
Pacinian corpuscle
Reticular dermis
Pressure & vibration
1.
2.
●
●
Palpable elevated solid mass
3. PAPULE — less than or equal to 5 mm (small)
4. PLAQUE — greater than 5 mm; confluence of papule
(large)
5. NODULE — 5–20 mm circumscribed solid skin
elevation
6. WHEAL — irregular, edematous skin area
Elevated lesion with fluid cavities
7. VESICLE — (small) less than 5 mm; containing serum
8. BULLAE / BLISTERS — (large) greater than 5 mm
9. PUSTULE — contains purulent material
Others
10. CYST — enclosed cavity with membranous lining,
which contains liquid or semisolid matter
11. TUMOR — large nodule (may be neoplastic)
12. TELANGIECTASIA — dilated superficial blood vessel
2. SECONDARY LESIONS
SECONDARY LESIONS
1. SCALE — superficial epidermal cells that are dead & cast
off from the skin
2. EROSION — superficial, focal loss of part of the epidermis;
heal without scarring
3. ULCER — focal loss of part of epidermis extending to
dermis; heal with scarring
4. FISSURE — deep skin split extending into the dermis
5. CRUST — dried exudate; “scab”
6. ERYTHEMA — skin redness
7. EXCORIATION — superficial, often linear, skin erosion
caused by scratching
8. EDEMA — swelling due to the accumulation of water in
tissue
9. HYPERKERATOSIS — abnormal skin thickening
II. SKIN DISORDERS
A. ACNE & RELATED DISORDERS
1. ACNE VULGARIS
ACNE VULGARIS
● most common dermatologic disease
● caused by hormonal & bacterial disorder of pilosebaceous
unit
● ↑ end organ sensitivity, ↑ follicular hyperkeratosis = blocks
the follicle canal
● comedones
B. TYPES OF LESIONS (Key Terms)
Primary Lesions
Secondary Lesions
1. PRIMARY LESIONS
PRIMARY LESIONS
● Flat spots — neither elevated nor depressed
1. MACULE — less than 1 cm
2. PATCH — greater than 1 cm
© jri
Severity
● MILD Acne Vulgaris
○ small papules & comedones
○ no nodules/cyst
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WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
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MODERATE Acne Vulgaris
○ papules predominate
○ few nodules, rare cysts
SEVERE Acne Vulgaris
○ nodules & cysts predominate
3. HIDRADENITIS SUPPURATIVA
HIDRADENITIS SUPPURATIVA
● severe, chronic, scarring
gland-bearing areas
Face, back, shoulders, chest
! Feature
Classic
Description
Treatment
Primary
● Comedones
● Papules
● Pustules
● Nodules
● Cysts
Secondary
● Erythema
● Scar
● Excoriation
Population
● Mild — topical antibiotics, benzoyl peroxide,
tretinoin
● Moderate — oral antibiotics
● Severe — oral antibiotics, 13-cos retinoic
acid
Classic
Description
Treatment
Patient Education
● Will not see improvement at least 6–8 weeks
2. ACNE ROSACEA
ACNE ROSACEA
● “rosacea” = rosy
● chronic acneiform disorder
● vascular dilation of central face
● range: mild erythema → severe sebaceous gland
hyperplasia accompanied by telengiectasia, pustules,
nodules
● eye involvement — keratitis, conjunctivitis
● RHINOPHYMA — hyperplasia of soft tissue of the nose
! Feature
Recurrent abscess formation to keratin
plugging of the distal follicle
After puberty; Obese patient
Primary
● Nodules
● Cyst
● Occasional
blackheads
●
●
●
●
Secondary
● Erythema
● Exudate
● Scar
● Sinus tract
● Edema
● Ulceration
Systemic antibiotics
Intralesional injection
Topical antibiotics
Referral
B. ARTHROPODS
1. SCABIES
SCABIES
● “scabo” (French) = to scratch
● considered infestation: 10–11 adult mites (30 days)*
● symptoms occurs: 3–6 weeks after primary infestation
Etiologic
Agent
Transmission
Sarcoptes scabies var. Hominis (0.3mm
diameter)
Skin-to-skin contact
Facial flushing
! Feature
Population
Older adults
Classic
Description
Primary
● Papules
● Pustules
● Nodules
● Cysts
● Telangiectasia
Treatment
● Topical AB & benozyl peroxide — papular &
pustular lesion
● Oral AB — nodular lesion
—
rhinophyma,
significant
● Referral
telangiectasia
Severe pruritis (worst at night)
Fingerwebs, wrists, side of hands & feet,
axilla groin, areola, extensor surface of
elbows & knees
Secondary
● Erythema
● Scarring
Classic
Description
Treatment
© jri
disease in the apocrine
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Infant’s face:
● Burrows (0.5–1.0 mm long linear or wavy
ridges), papule, pustule, vesicle, nodule
● Erythema, crust, excoriation scale
● Topical Medication
○ Permethrin 5% cream: safe for
children older than 2 months (one
application)
○ Lindane 1%: kill remaining larva (2
applications)
○ Crotamiton 10%: not safe for
children & pregnant women
○ Precipitated sulfur: safe for
children & pregnant women;
messy & has unpleasant odor
Antihistamine,
Topical
● Oral
Corticosteroids
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WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
2. PEDICULOSIS CAPITIS (Head Lice)
3. INSECT BITES
PEDICULOSIS CAPITIS (Head Lice)
INSECT BITES
PEDICULOSIS CAPITIS
Etiologic
Agent
Etiologic
Agent
Pediculus humanus capitis
! Feature
Transmission
Head-to-head contact, sharing of combs
Population
Severe pruritis in the scalp
! Feature
Classic
Description
Scalp (sides & posterior aspects)
Classic
Description
Primary
● Papules
Secondary
● Excoriation
● Erythema
● Crust
Diagnosis
Observation of the scalp
Treatment
● Pediculicides
○ Permethrin 1%: for head only (not
pubic lice)
● Nit removal
● Environmental treatments
2. PEDICULOSIS PUBIS (Phthiriasis)
! Feature
Population
Phthiriasis pubis
area
+
Primary
● Papules
● Macules
Secondary
● Erythema
● Excoriation
● Crust
Treatment
● Prevention of reexposure (most effective)
C. BACTERIAL DISEASES
1. IMPETIGO
IMPETIGO
● superficial skin infection
● “scabby eruption that attacks”
Predisposing
Factors
Young, sexually active adults
B-hemolytic Streptococcus (Group A)
○ if lesion is crusted
S. aureus (Group B)
○ if lesion is bulbous
Warm, moist climate, underlying excoriated
skin conditions
Face, arms, legs, maybe anywhere
Pubic region, axillary hairs (less often),
eyelashes
Classic
Description
Primary
● Papules with
central punctum
● Vesicles or bullaes
(if severe)
Irregular-grouped pruritic papules, old lesion
on reexposure
Etiologic
Agent
Severe itching in the pubic
eczematization, possible infection
Children — play outdoors
Diagnosis
PEDICULOSIS PUBIS (Phthiriasis)
● “crabs”
Etiologic
Agent
Pruritic lesion, allergic type reaction (papular
urticaria), marked edema, erythema
Exposed surfaces, grouped irregularly
Common in school-aged children
Population
Classic
Description
Secondary
● Blue-gray
pigmentation
● Excoriation
● Erythema
● Crust
Diagnosis
Careful observation — underwear may have
brown specs (feces)
Treatment
● Pediculicides
○ Permethrin 1%: for head only (not
pubic lice)
● Nit removal
● Evaluation for other sexually transmitted
disease
● Environmental treatments
© jri
Mosquitoes, chiggers, fleas, flies
Primary
● Vesicles
● Pustules
Secondary
● Yellow/Honeycolored crust
● Erythema
● Erosions
Diagnosis
● Lesions
○ Vesicular before crusting
○ **difficult in children with
honey-colored crust lesion
● Gram Stain
○ Gram+ cocci in clusters —
Staphylococcus
○ Gram+ cocci in chain —
Streptococcus
Treatment
Oral antibiotics — preferred therapy for
multiple lesions
Topical ointments — for limited diseases
only
Culture with sensitivitiy — if infection is still
resistant
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WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
2. ERYSIPELAS
ERYSIPELAS
● “red skin”
● SSx:
○ Chills, headache, fever
○ Tachycardia
○ Confusion
○ Hypotension
● typically arises from small inapparent breaks in the skin
Predisposing
Factors
Lymphatic involvement with Group A
Population
Infants, young children, older adults
Primary
● Plaque
3.
Secondary
● Marginated
erythema
● Edema
Diagnosis
● Marginated erythema
● Systemic SSx
Treatment
Oral antibiotics
● Uncomplicated cases: 10 days
● Severe cases: 2–3 weeks
Antibiotics (IV)
● Toxic, debilitated, or elderly patients
● Children with facial involvement
3. FOLLICULITIS
Predisposing
Factors
Classic
Description
Diagnosis
S. aureus
Diabetes mellitus,
immunodeficiency
Superficial
● Scalp,
extremities (any
hair-bearing
area)
● Primary:
Pustule pierced
by hair
● Secondary:
Erythema
obesity,
D. FUNGAL INFECTIONS
1. DIAGNOSIS OF FUNGAL INFECTIONS
Microscopic examination of fungi in 10% potassium
hydroxide (KOH)
○ What to look for?
Fungal culture
○ Examine it every 2 weeks for 4–8 weeks
○ (+) If there are changes from yellow → red
Histologic biopsies
○ If 1 & 2 are negative but high suspicion of fungus
2. TINEA INFECTIONS
FOLLICULITIS
● pustular infections that involve hair follicle
● range from:
○ SUPERFICIAL — involves only the terminal part
○ DEEP — the whole depth (furuncle, carbuncle)
● can be secondary infection in excoriated lesion from
scabies, insect bite, eczema
Etiologic
Agent
1.
2.
Sites of chronic edema, old scars,
extremities, face
Classic
Description
Treatment
TINEA INFECTIONS
● tinea = “moth”
● dermatophytes — non-invasive
a. Epidermophyton
b. Trichophyton
c. Microsporum
● Animals: usually hosts; has the most inflammatory
response
● Human: least amount of inflammatory response
● named according to location
○ T. capitis = head
○ T. manus = hand
○ T. pedis = foot
○ T. cruris = groin
○ T. corporis = body
○ T. unguium = nail
TINEA CAPITIS
Classic
Description
malnutrition,
Deep
● Any hair-bearing
area; MC in site of
friction (buttocks,
groin)
● Primary: Nodule
● Secondary:
Erythema, edema,
exudate, draining
sinuses
● Superficial: Take note the primary
description
● Deep: (+) Erythematous nodule with
fluctuance
Diagnosis
Primary
● Plaques
● Papules
● Pustules
● Nodules
Secondary
● Scale
● Alopecia
● Erythema
● Exudate
● Edema
● Direct microscopic examination using KOH
○ look for HYPHAE or SPORES
○ if severe, KOH may produce (–)
result
● Culture
● Wood’s lamp
○ bright green fluorescence in hair
shaft = (+) Microsporum
TINEA CORPORUS / TINEA CARCINATA
● “body ringworm”
● MAJOCCI’S GRANULOMA — commonly affects women’s
legs
○ follicular involvement
○ (–) Annular plaque
○ Dx: Examine plucked hair for hyphae
Etiologic
© jri
● Warm compresses (20–30 mins, 3–4x a
day)
● Oral antibiotics: Cephalexin, Cloxacillin
● Incise & drain the lesion
● For recurrent lesion: Culture specimens
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Tricophyton rubrum (MC pathogen)
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WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
Agent
Mode of
Transmission
Onset
Population
Classic
Description
Direct human contact
Animal exposure
Soil
Isolated lesion → satellite areas
All ages
Trunk, limbs, face
Lesions: ANNULAR — with peripheral
enlargement, central clearing,
well-demarcated margins
ITCHY
Primary
● Papules
● Plaques
Diagnosis
© jri
Secondary
● Erythema
● Scale
● KOH microscopic examination
leading edge — not center
● Culture
from
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WEEK #8 - MODULE #3: SKIN INFECTIOUS DISORDERS
i. APPENDIX
Table 1. Acne & Related Disorders (Summary)
DISEASE
KEY FEATURE
POPULATION
LOCATION
Acne vulgaris
Papules, comedones, nodules,
cyst
Lesion at varying stage
Adolescents
Adults
Face, back, shoulder, chest
Acne rosacea
Erythemathous component
Telangiectasia
No comedones
Older adults
Central face
Hidradenitis suppurativa
Recurrent abscess formation
After puberty
Obese patient
Axilla, areola, anogenital region
© jri
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