Dermatology 2 (infections) Flashcards
Who does impetigo usually affect?
Children
Which bacteria cause impetigo?
Staph aureus
Strep pyogenes
Which bacteria is more common in tropical areas?
Streptococcal - more common in warmer/humid climates
What are the 2 types of presentation of impetigo?
Non-bullous
- tiny pustules/vesicles that rapidly evolve
- honey crusted plaques
- satellite lesions due to autoinoculation
Bullous
- thin roof, easily rupture
- painful
How do you treat impetigo?
Flucloxacillin or clarithromycin (especially if bullous)
Good hygiene
What is a complication of impetigo?
Staphylococcal scalded skin syndrome (when S. aureus releases epidermolytic toxins)
What are the main risk factors of cellulitis?
Diabetes Cancer Immunodeficiency Venous insufficiency Obesity
Which bacteria most commonly cause cellulitis?
Staphylococcus aureus
Group A beta-haemolytic streptococci (e.g. Strep pyogenes)
Clostridium perfringens - surgical wounds
Suggest appropriate therapy for each of the following:
a) Staphylococcus aureus
b) Streptococcus pyogenes
c) MRSA -
a) Staphylococcus aureus - flucloxacillin or vancomycin/clarithromycin in allergy
b) Streptococcus pyogenes - IV benzylpenicillin with oral switch to amoxicillin after 48 hrs or clarithromycin/clindamycin/vancomycin
c) MRSA - vancomycin with oral switch to clarithromycin, tetracycline or linezolid
What would the area look/feel like? What area of body is usually affected?
Erythema, swelling, warmth, pain
Lower limb
What additional presentation would be seen in clostridium perfringens cellulitis?
Crepitus (anaerobic organism)
What are some complications of cellulitis if left untreated?
Abscess
Gangrene
Necrotising fasciitis
Osteomyelitis
What organisms cause folliculitis?
Bacterial - S. aureus
Fungal - Pityrosprorum ovale
Virus - HSV, herpes zoster
What causes scabies?
Parasitic infection of sarcoptes scabiei mite that deposits eggs into epidermal burrow
What are the symptoms of scabies? Where are the symptoms usually felt?
Intensely pruritic papular eruption
Especially in interdigital and flexural creases
When are the symptoms of scabies worse?
at night or after a hot bath/shower
How do you treat scabies?
Permethrin - topical over the whole body
Antihistamines
How can you diagnose scabies?
Ink burrow test - with a marker pen draw along any bumps then wipe the pen away. If there are scabies, lines of ink will remain in the burrows.
What is the difference between HSV1 and HSV2?
HSV1 - oral infections e.g. cold scores (however can cause genital infection if transferred from cold sores)
HSV2 - primarily genital infection
Is herpes simplex curable?
No it is a life-long latent systemic infection. It lies dormant in CNS sensory ganglia.
What can cause reactivation of herpes simplex?
Reactivation from CNS sensory ganglia due to:
- Injury
- UV light
- Stress
- Hormones
How does HSV2 present?
Initial prodrome - fever, headache, malaise
Discharge, oedema, dysuria
Many painful blisters
Tender bilateral lymphadenitis
What is the incubation time for HSV2?
3-7 days
What CNS conditions can herpes simplex viruses cause?
HSV-1 - encephalitis
HSV-2 - meningitis
What is the treatment for herpes simplex virus?
Aciclovir
What virus is chickenpox caused by?
Varicella zoster virus = HHV-3
What is the incubation period for VZV and when is someone infectious?
Incubation period: 14 days (1-3 weeks)
Infectious 1-2 days before symptoms and 5 days after onset
Describe a chicken pox rash
Starts with small erythematous macules, that progress to papules and finally clear vesicles. The vesicles burst and crust over.
Highly pruritic
Limb sparing
Who should avoid contact with someone with chickenpox?
Pregnant women
Give them Ig if they are not immune
What are some serious complications of chickenpox?
Viral pneumonia
Encephalitis
What virus is shingles caused by?
Herpes Zoster i.e. reactivation of varicella zoster virus from CNS sensory ganglia
How does shingles present?
Prodrome = burning, itching, paraesthesia, malaise
Eruptive phase = acute neuritic pain, vesicles and erythematous swellings affecting an isolated dermatome
How long is shingles infectious for?
Until all vesicles have crusted over
Where would a shingles infection cause more serious problems?
Ophthalmic VZV can cause blindness
Facial nerve -> Ramsay-Hunt syndrome which can cause facial paralysis and hearing loss in affected ear (due to proximity of vestibulocochlear nerve)
What virus causes molluscum contagiosum and which subtype is most common?
MCV (a pox virus)
4 subtypes - MCV1 is most common
What is the incubation period for MCV?
2-12 weeks
How does molluscum contagiosum present?
Dome-shaped, flesh-coloured or pearly white papules with central umbilication distributed in clusters
What fungal infection causes patches of altered skin pigmentation?
Pityriasis versicolor caused by Malassezia yeasts
What parts of the body are most commonly affected by pityriasis versicolor?
Sebum-rich sites e.g. back, chest, face, upper arms
Aside from altered pigmentation, what else might be present in pityriasis versicolor?
Superficial fine powdery scale (can be seen by stretching the skin)
What is first-line treatment for pityriasis versicolor?
Antifungal shampoo e.g. ketoconazole shampoo
What can occur due to poor steroid inhaler technique? What does it look like?
Oral candidiasis
Patches of curd-like, white/yellow plaques on tongue and palate
Which type of Candida causes oral and vaginal candidiasis?
Candida albicans
How does vaginal candidiasis present?
Itching, soreness, inflammation, discharge, dyspareunia (pain on intercourse), dysuria
Who is particularly at risk of recurrent candida infections?
Immunocompromised
Antibiotic use
Diabetics
What causes ring-shaped lesions with red scaly border and clear centre?
Tinea corporis
AKA ring-worm
Who gets tinea pedis and what does it look like?
‘Athlete’s foot’ - moist environment and laceration of skin
White, cracked, softened areas between toes
Diffuse scaling on sole/side of foot
Inflammatory vesicobullous eruption on soles
What is the fungal infection of a nail called?
Tinea unquium
What can be used to detect fungal infections?
Wood’s light = UV light
Causes fungus to fluoresce
