Dermatology - Skin Infections Flashcards
(138 cards)
1
Q
What virus causes chicken pox?
A
Varicella zoster virus (VZV)
2
Q
Transmission of VZV?
A
Highly contagious. Droplet spread or direct skin contact with vesicle fluid, with the virus entering the body via the URT.
3
Q
Incubation period of VZV?
A
10-14 days but can be up to 21 days.
4
Q
What is the contagious period of VZV?
A
Chickenpox is contagious 1-2 days before rash appears until blisters have scabbed over (5-10 days).
5
Q
Define a vesicle
A
Small, raised, fluid-filled lesion
6
Q
Describe the rash first seen in chickenpox
A
Chickenpox is an acute disease characterised by a vesicular rash
7
Q
Prodromal presentation of chickenpox?
A
- Vesicular rash
- High fever (38-39) – often first symptom
- General malaise
- Anorexia
- Headache
- Nausea
8
Q
What is a prodrome?
A
an early symptom indicating the onset of a disease or illness
9
Q
Describe the progression of the rash in chickenpox
A
- Begins as small erythematous macules on the scalp, face, trunk, and proximal limbs
- These macules develop into papules, vesicles and pustules which appear in crops
- Crusting of the vesicles and pustules usually occurs after 5 days, at which point new vesicle formation has ceased (no longer contagious after all lesions have crusted over)
10
Q
General advice for management of chickenpox?
A
- Hydration
- Avoidance of scratching (keep fingernails short) – due to risk of infection and scarring
- Avoidance of pregnant women, neonates and immunocompromised
11
Q
What analgesia should be avoided in chickenpox? Why?
A
NSAIDs → increase the risk of necrotising soft tissue infections
12
Q
Symptomatic management of chickenpox?
A
- Paracetamol
- Sedating antihistamines (chlorphenamine)
- Emollients and calamine lotion for itch
- Antivirals → Consider oral acyclovir if adolescent or adult presents within 24 hours of rash onset (especially if severe or at high risk of complications)
13
Q
What antiviral can be considered in the management of chickenpox?
A
Aciclovir
14
Q
Possible complications of chickenpox?
A
- Bacterial infections of the skin and soft tissues in children, including Group A streptococcal infections.
- Infection of the lungs (pneumonia)
- Infection or swelling of the brain (encephalitis, cerebellar ataxia)
15
Q
What is Reye’s syndrome?
A
A rare complication seen in children and young adults recovering from viral illness and thought to be related to aspirin use
16
Q
What is Reye’s syndrome thought to be related to?
A
Aspirin use → AVOID in young children
17
Q
After chickenpox infection, where can the virus lay dormant?
A
in the sensory dorsal root ganglion cells and cranial nerves
18
Q
What can chickenpox reactivate later as?
A
Shingles (Herpes Zoster) or Ramsay Hunt syndrome
19
Q
What is Ramsay Hunt syndrome?
A
Ramsay Hunt syndrome occurs when a shingles outbreak affects the facial nerve near one of your ears. In addition to the painful shingles rash, Ramsay Hunt syndrome can cause facial paralysis and hearing loss in the affected ear.
20
Q
Who does shingles (herpes zoster reactivation) commonly occur in?
A
Commonly occurs in the elderly and immunosuppressed (shingles in young adults should prompt investigation for an underlying immune condition)
21
Q
Give some triggers for shingles reactivation
A
- Nerve pressure
- Radiotherapy at level of nerve root
- Spinal surgery
- Infection
22
Q
Describe the rash in shingles
A
- Can manifest first as a tingling sensation severe pain or in a dermatomal distribution
- Progresses to erythematous papules occurring along one or more dermatomes within a few days → develop into fluid-filled vesicles (blistering rash) which then crust over and heal.
23
Q
What symptoms can accompany the rash in shingles?
A
May be associated with viral symptoms – fever, headache, malaise, lymphadenopathy in affected area
24
Q
What is the danger if the trigeminal nerve is affected in shingles?
A
Ophthalmic shingles
25
Management of uncomplicated shingles?
* Rest and pain relief
* Protection for rash e.g. Vaseline
* Isolation – infectious to people who have not had chickenpox
26
When can oral antivirals (aciclovir) be indicated in shingles?
* Oral antivirals if **immunosuppressed** or if **eye** involvement
* IV antivirals if severe disease
* Routinely prescribed in people \>50
27
What can ophthalmic shingles lead to?
Corneal ulcers, scarring and blindness if eye involved
28
What nerve is affected in Ramsay Hunt syndrome?
Facial nerve (VII)
29
What nerve is affected in ophthalmic shingles?
Trigeminal nerve (V)
30
What is the most common complication of shingles?
Post-herpetic neuralgia - persistence/re-occurrence of pain in the same area more than 1 month after onset of shingles
31
What can reduce the chance of post-herpetic neuralgia?
Aciclovir
32
What is a risk factor for post-herpetic neuralgia?
Age
Facial infections
33
What are the 2 types of HSV. What infections does each cause?
* Type 1 (HSV1) → oral & facial infections
* Type 2 (HSV2) → genital & rectal infections, often transmitted sexually
BUT either virus can affect other areas of skin/mucous membranes.
34
Transmission of HSV?
Spread by direct or indirect contact. Virus can be transferred to new skin sites by the patient during an attack.
35
Is type 1 or type 2 HSV often more symptomatic?
Type 2
36
What does type 1 HSV mostly present as? What age group?
Gingivostomatitis (gingivitis is inflammation of gums, stomatitis is inflammation of mouth and lips) in **children 1-5 y/o:**
* Fever
* Restlessness
* Excessive dribbling and bad breath
* Gums are swollen/red/bleeding – eating is painful
* White vesicles → these turn into yellow ulcers on tongue, throat, palate and inside cheeks
* Lymphadenopathy
37
What does type 2 HSV mostly present as?
* Genital herpes after onset of sexual activity
* Painful vesicles, ulcers, swelling, redness for 2-3 weeks
* In males – glans, foreskin and shaft
* Anal herpes more common in MSM
* Females – vulva and vagina
* Often painful to urinate
* Cervical infection may lead to severe ulcers
38
What is diagnostic test for HSV?
Swab base of ulcer and send off for nucleic acid amplification tests (NAATs).
39
Is recurrence of type 1 or 2 HSV more common?
Type 2
40
What are some triggers for HSV recurrence?
minor trauma, URTAs, sun exposure, hormones (e.g. prior to menstruation), stress
41
Complications of HSV infection?
* Eye infection – swollen eyelids and conjunctiva
* Throat infection – painful and affects swallowing
* Eczema herpeticum
* Erythema multiforme
* Disseminated/widespread infection – serious in immunocompromised
42
How can HSV lead to eczema herpeticum?
Occurs when patient with eczema becomes infected by either HSV or VSV through breaks in skin
43
How does erythema multiforme present?
Targetoid lesions with central blisters
44
What is the most typical skin manifestation of HIV?
**Pruritic papular eruption (PPE)**
45
How does pruritic papular eruption present?
* Itchy
* Discrete scratched red bumps
* Symmetrical
* Diffuse
* Extremities and trunk commonly affected
* No mucosal. palmar or webbing involvement
46
What are viral warts? What virus are they caused by?
Very common non-cancerous growths.
Human papillomavirus (HPV)
47
Pathophysiology of warts?
Infection occurs in **superficial epidermis**, causing **keratinocyte proliferation** and **hyperkeratosis**.
48
Describe the presentation of a viral wart
**Hard surface** with **black dot** in the middle of each scale – this is a thrombosed capillary blood vessel
49
What are plantar warts?
Veruccas - tender, inward growing ‘myrmecia’ with clusters of mosaic warts (less painful)
50
Topical treatment of warts?
Salicylic acid – removes dead surface cells (keratolytic)
51
Other treatment options for warts?
* Cryotherapy
* Electrosurgery
52
What pathogen causes molluscum contagious?
Molluscum contagiosum virus - type of poxvirus
53
Risk factors for molluscum contagiosum?
* Children \<10 y/o
* Warmer climates
* Wet conditions e.g. swimming pool
* Overcrowded environments
* Atopic eczema (deficient skin barrier)
* Immunocompromised
54
Transmission of molluscum contagiousum?
* Skin-to-skin
* Indirect e.g. towels, bedsheets
* Autoinoculation (shaving or scratching)
* Sexual transmission
55
Describe the clinical presentation of molluscum contagiosum
* Clusters of **small** (1-6mm)**, round papules** (raised bumps) – can be few to 100s in a local area
* White, pink or brown (fresh coloured)
* Often **shiny** with umbilicated pit
* Papules contain **white, cheesy** material
* Arise in **warm/moist** places e.g. flexures
56
If bacterial superinfection infection occurs in molluscum contagiosum as a result of scratching, what can you use to treat it?
Antibiotics (topical fusidic acid or oral flucloxacillin)
57
What 2ary bacterial infection can you get from molluscum?
Impetigo
58
Is impetigo bacterial or viral?
Bacterial
59
What is impetigo?
Common acute superficial bacterial infection affecting the skin caused by Staphylococcal and Streptococcal bacteria.
60
What 2 pathogens commonly cause impetigo?
1. **Staph**. **aureus** - most common
2. Strep. pyogenes
61
Give some risk factors for impetigo
* Atopic eczema
* Scabies
* Skin trauma – bacteria enters skin via break in skin:
* Chickenpox
* Insect bite
* Wound
* Burn
* Dermatitis
62
What are the 2 types of impetigo?
1. Bullous (blisters)
2. Non-bullous (sores)
63
What pathogen ALWAYS causes bullous impetigo?
Staph. aureus
64
Where does non-bullous impetigo typically occur?
Typically occurs around nose or mouth – staph/strep invade a minor trauma site
65
Describe the lesions in non-bullous impetigo
* exudate from the lesions dries to form a **‘golden crust’:**
* Pink macule → vesicle/pustule → crusted erosion
66
Does non-bullous impetigo or bullous tend to cause systemic symptoms?
Bullous
67
Management for non-bullous impetigo?
* Topical fusidic acid, antiseptic cream (hydrogen peroxide 1% cream)
* Oral flucloxacillin in more widespread/severe impetigo
68
Describe the lesions in bullous impetigo
* Small vesicles → flaccid transparent bullae → burst and form ‘golden crust’
* Lesions can be painful and itchy
69
Does bullous impetigo scar?
no
70
Management for bullous impetigo?
Flucloxacillin
71
How long should children with impetigo stay off school?
* Children must avoid school until **crust dries** OR
* Avoid school until they have completed 48 hours of antibiotic treatment
72
Potential complications of impetigo?
* **Soft tissue infection** e.g. cellulitis – risk of subsequent bacteraemia (sepsis)
* **Scarring**
* **Staphylococcal scalded skin syndrome**
* **Post-streptococcal glomerulonephritis**
* **Scarlet fever**
73
What is staphylococcal scalded skin syndrome?
* **Bullous** impetigo can lead to severe infections where the lesions are widespread → this is staphylococcus scalded skin syndrome
* Dermatological emergency
74
What is cellulitis?
A bacterial soft tissue infection of the **dermis** and **subcutaneous** **tissue**.
75
Risk factors for cellulitis?
* Advancing age
* Immunocompromised e.g. diabetic
* Predisposing skin condition e.g. ulcers, pressure sores, trauma, lymphoedema (breaches in skin)
76
What pathogens typically cause cellulitis?
* Staphylococcus aureus
* Group A Streptococcus (S. pyogenes)
* Group C Streptococcus (S. dysgalactiae)
* MRSA (less common)
77
Investigations for cellulitis?
* Blood tests including culture
* Skin swab for culture
78
What is the 1st line Abx in the management of cellulitis?
**Flucloxacillin** (oral or IV depending on severity)
79
Classification of cellulitis:
* Class 1 → No systemic toxicity or comorbidity
* Class 2 → Systemic toxicity or comorbidity
* Class 3 → Significant systemic toxicity or significant comorbidity
* Class 4 → Sepsis or life-threatening
80
Which class of cellulitis requires IV Abx?
Class 3 or 4 (also consider admission for frail, very young or immunocompromised patients)
81
Necrotising fasciitis vs cellulitis?
* This can appear similar to cellulitis.
* It affects the skin, subcutaneous tissue, **_fascia**_ and _**muscle_**.
* Oedema may extend beyond area of erythema (may blister or have bullae)
* **Pain** is far more extreme than cellulitis
* **Crepitus** on palpation (soft tissue gas)
* More rapid progression
* Patient more **systemically unwell**
82
What is erysipelas?
Cellulitis refers to the infection of the **dermis** and **subcutaneous** **tissue**.
Erysipelas refers to the infection of the **dermis** and the **_upper_** subcutaneous tissue (i.e. is an acute, superficial form).
83
What pathogen almost always causes erysipelas?
Almost all are caused by group A beta-haemolytic streptococci (unlike cellulitis).
84
Give some risk factors for erysipelas
* Previous erysipelas/cellulitis
* Venous insufficiency
* Immune deficiency (e.g. diabetes, HIV, alcoholism)
* Breaks in skin barrier (bites, ulcers, psoriasis, eczema)
* Obesity
* Fissured toes or heels due to athlete’s foot or tinea pedis – cause skin breakage allowing entry of infective organisms
* Pregnancy
85
Abx management for **severe** cellulitis?
Flucloxacillin + benzylpenicillin
86
What is folliculitis?
Group of skin conditions where hair follicles are inflamed (e.g. acne, rosacea)
87
Describe the lesion in folliculitis
Tender red spot, often with surface pustule
88
Folliculitis can be bacterial, viral, fungal or infestations. Give some example pathogens for each
Bacterial:
* Staph. aureus
* Pseudomonal aeruginosa ('spa pool folliculitis')
Viral:
* HSV
* HZV
Fungal/Yeast:
* Candida
* Tinea capitis
Infestations:
* Hair follicle mas
* Scabies
89
Management of folliculitis?
* Careful hygiene
* Antiseptic cleanser
* Bacterial → topical/oral antibiotics e.g. tetracycline
* Viral → acyclovir
* Yeast/fungi → topical/oral antifungal
90
What is intertrigo?
Rash in **flexures**/**body** **folds** that may affect one or multiple sites (e.g. behind ears, axillae, groin, buttocks, finger/toe webs)
91
Risk factors for intertrigo?
* Obesity
* Genetic tendency
* Hyperhidrosis (excessive sweating)
92
Why does intertrigo occur in body folds?
* Flexural skin has high surface temperature
* Moisture is stopped from evaporating due to folds
* Friction from movement of fold skin can cause chafing
* Bacteria and/or yeast multiply in warm, moist settings
93
Does infectious intertrigo cause unilateral or bilateral lesions?
Unilateral
94
Does inflammatory intertrigo cause unilateral or bilateral lesions?
Bilateral
95
Management of inflammatory intertrigo?
* Low potency topical steroids e.g. hydrocortisone
* Calcineurin inhibitors e.g. tacrolimus
96
potential complications of intertrigo?
* **Soft tissue infection** e.g. cellulitis → risk of subsequent bacteraemia
* **Staphylococcal scalded skin syndrome** → dermatological emergency
* **Post-streptococcal glomerulonephritis**
97
What is post-streptococcal glomerulonephritis?
**a rare kidney disease that can develop after group A strep infections**.
98
What is staphylococcal Scalded Skin Syndrome (SSSS)? What is it caused by?
Severe desquamating rash that affects **infants.**
## Footnote
Caused by endotoxins released by S. aureus.
99
Clinical features of staphylococcal Scalded Skin Syndrome (SSSS)?
* Superficial fluid-filled blisters
* Erythroderma (erythema \>90% of body surface)
* Desquamation (peeling of epidermis) and Nikolsky sign is positive
* Oral mucosa unaffected unlike TEN
* Fever & irritability – due to infective cause
100
What is desquamation?
peeling of epidermis
101
What is Nikolsky sign?
superficial epidermis can be dislodged by a slight shearing force – seen in SSSS, TEN and pemphigus vulgaris
102
What is red man syndrome?
Red man syndrome is **an infusion-related reaction peculiar to vancomycin**
103
What are dermatophytes?
Fungi that require keratin for growth. These can cause superficial infections of the skin, hair, and nails.
104
What is tinea?
Tinea is a dermatophyte (ringworm) fungal infection. Generally more at risk of development if area of skin is **warm** & **moist**.
105
What is tinea:
* capitis
* corporis
* cruris
* pedis
* unguium
* head
* body
* groin
* foot
* nail
106
What is athlete's foot also known as?
Tinea pedis
107
Describe the lesions in tinea infections
Characterised by a **red, scaly patch** which classically has an area of central clearing.
108
Diagnosis of tinea infections?
* Skin scrapings
* Hair/nail clippings
* If the dermatophyte is Microsporum canis, under a **Wood’s lamp** affected areas with fluoresce
109
Give 2 systemic antifungal agents that can be used for tinea capitis or onychomycosis (infection of the nail with onycholysis)
1. Terbinafine
2. Itraconazole
110
Why should topical steroids be avoided in tinea infections?
Can cause tinea **incognito**
111
What is tinea incognito?
Tinea incognito is a term used to describe a tinea infection modified by topical steroids. Topical steroids **suppress the local immune** **response** and allow the fungus to grow easily.
112
Define pityriasis
Used to describe skin conditions in which the scale appears similar to bran.
113
Define versicolor
Implies multiple colours
114
What is pityriasis versicolor?
Common yeast infection of the skin. Not infectious but may affect more than 1 family member.
115
What pathogen causes pityriasis versicolor?
***Malassezia Furfur*** (fungi).
116
Malassezia are part of the normal skin microbiota. Where are they usually found?
usually found sparsely in the seborrhoeic areas (scalp, face and chest) without causing a rash.
117
What type of environment can trigger pityriasis versicolor?
Humid, warm environments (may clear in winter and recur in summer)
118
What are the 2 types of pityriasis versicolor?
Brown → hyperpigmented (large melanosome within basal melanocytes)
White → hypopigmented
119
Can pityriasis versicolor patches tan on sun exposure?
No
120
Management for pityriasis versicolor?
* Treat known triggers:
* E.g. immunosuppressive condition
* Warm, wet environment
* Topical antifungals e.g. terbinafine
* Oral antifungals if severe or widespread e.g. itraconazole
121
Why should pityriasis versicolor **not** be treated with topical steroids?
Can cause **tinea incognito**
122
What is candidiasis? Most common pathogen causing it?
Yeast infection (most common ‘candida albicans’). Can infect the mouth, GI tract, genitals, nails and skin in general:
* Oral
* Angular cheilitis
* Vulvovaginal candidiasis
123
Where is candida albicans a normal inhibitant of without problems?
GI tract
124
Clinical features of candidiasis?
* White plaques with erythema
* Itchy
125
Pharmacological management of oral candidiasis?
Nystatin
126
What is scabies?
A highly contagious skin infection caused by mites.
Scabies is more common than you think. When someone presents with an **itchy rash**, ask whether **anyone they live with has a similar rash** and check between their **finger webs** **for little red dots and track marks** that may indicate scabies.
127
What is the cause of scabies?
Parasite mites (*Sarcoptes scabiei*) burrow under skin.
128
Transmission of scabies?
* **Close/direct contact** (skin-to-skin contact with a person with scabies, can be brief e.g. holding hands or sexual contact)
* Indirectly via **fomites** (less common) e.g. bedding, clothes, towels
* Highly contagious
129
Who is scabies more common amongst?
Seen more commonly among disadvantaged populations – is considered a neglected tropical disease
130
Risk factors for scabies?
* Children
* Elderly
* Living conditions (poverty, overcrowding)
* Immunosuppression
131
Pathophysiology of scabies?
A delayed type IV hypersensitivity reaction results in symptoms around 30 days or even up to 8 weeks) after the initial infection.
132
What do the clinical features of scabies infection primarily result from?
from a **local allergic reaction** to the presence of the scabies mite, rather than directly being caused by the mite itself.
133
Clinical features of scabies?
* **_Intensely itchy_** rash that usually affects the **inter-web spaces** (between fingers), flexures of the wrist, axillae, abdomen, and groin
* Itchy is classically **_worse at night_** – sleep disturbance
* Rash usually **papular** or **vesicular** (with surrounding dermatitis)
* **_Superficial burrows_** may often be seen – classically found in the webbed spaces between fingers
134
What should you ask about in patient history in scabies?
* Social history for risk factors e/g/ poor living conditions, overcrowding
* Potential contacts
* Additional holistic support
135
What is Crusted (Norweigan) Scabies? Who is it typically seen in?
* A severe variant of scabies where an individual is infected with thousands or millions or mites (compared with 5-20 in typical infection)
* Often seen in immunocompromised
136
1st line management of scabies?
Topical **_permethrin_** cream 5% (or malathion lotion)
137
In scabies, how can the chance of reinfection be minimised?
* Treat all members of household & all contacts on the _same day_
* Good hygiene – wash all bed linen, toys, clothes etc
138
Scabies can lead to a 2ary bacterial infection due to patients scratching the pruritic rash. What pathogens are most commonly responsible for this?
Most common S. pyogenes or S. aureus
