Dermatology Flashcards
1
Q
Parvovirus B19 (slapped cheek) background
A
Epidemiology
- most adults are seropositive
- infection most common in school
- occurs in endemics
- > up to 50% of exposed students develop disease
- nearly half of pregnant women seronegative
- > risk to fetus
- winter seasonality
Aetiology
- spread
- > respiratory droplets
- > fomites (unenveloped)
- > vertical
- > haematogenous (blood transfusion/IV drug use)
Pathophys
- directly cytotoxic to RBC progenitor cells
- > replicates within RBC progenitors in bone marrow
- > ineffective erythropoiesis
- rash and arthralgia
- > due to immune complex disease
2
Q
Measles background
A
Epidemiology
- a leading cause of mortality kids <5
- predominately in unvaccinated people/areas
- vaccinated populations at risk when rates are low
Aetiology
- spread
- > person-to-person
- > aerosol for 2 hours
- highly contagious
- > 90% infection rate for susceptible individuals
- at risk individuals
- > too young to be vaccinated
- > won’t or can be vaccinated
- > single or failed vaccination
Pathophys
- immunity is lifelong
- virus enters respiratory mucosa or conjunctiva
- incubation period up to 3 weeks
- infectious for up to 1 week prior to symptoms
- complications
- > leukopenia and immunocompromise
- > diarrhoea
- > pneumonia
- > encephalitis
3
Q
HFM disease background
A
Epidemiology
- under school age
- can occur in endemics
Aetiology
- virology
- > multiple serotypes of enterovirus species
- > most common enterovirus species is enterovirus A
- > most common group is coxsackie A and enterovirus
Pathophys
- transmission
- > as usual for enterovirus
- > can be from ingestion of vesicle secretions
4
Q
Measles evaluation and management
A
Hx
- Prodrome
- > up to 1 week
- > flu like illness
- > cough/coryza/conjunctivitis
- > koplick spots
- Exanthemous phase
- > lymphadenopathy
- > pharyngitis
- > worsening respiratory symptoms
- > cephalocaudal erythematous maculopapular rash
Exam
- Vitals
- > febrile
- Koplick spots
- > white/blue/grey papules
- > erythematous base
- > buccal, inside lips, palate
- Examthem
- > blanchable erythematous maculopapular rash
- > coalesces
- > spares hands and feet
- Lungs
- > pneumonia
- Neuro
- > encephalitis
Investigations
- FBC
- > neutropenia
- Measles serology
- > IgM +ive up to 2 weeks post rash
- > IgG = previous/immunisation
Management
- Admit
- > seizures
- > amnesia
- > paralysis
- Supportive
- > paracetamol
- > NSAIDs
- > hydration
- Vitamin A supplementation
- Prevention
- > infectious 1 week prior to rash
- > avoid unvaccinated + pregnant women
5
Q
HFM disease evaluation and management
A
Hx
- Prodrome
- > sore throat/poor feeding
- > fever
- > systemic symptoms in herpangina
- Endanthem + exanthem
- > appears days after fever begins
- > begins as pink patches
- > becomes vesicles with erythematous halos
- > rupture into ulcers
- > leaves no scars
- > non pruitic
Exam
- Vitals
- > febrile
- Endanthem
- > mouth
- > palate
- > pharynx
- Exanthem
- > dorsal and palmer foot and hands
- > can be widespread
Investigations
- Usually not necessary
- > PCR
- > viral culture
Management
- Prevention
- > hand hygiene after blisters, cough/sneeze, toileting
- > avoid sharing items (cutlery, toothbrush etc)
- > avoid school/day care until blisters dry
- > note virus shed in stools for weeks/months after
- > safety net (blisters last for about a week)
- > don’t pop blisters
- Public health
- > not notifiable
- > consider informing school/day care
- Supportive
- > fluids/electrolytes
- > analgesia (NSAIDs/paracetamol)
6
Q
Roseola infantum background
A
Epidemiology
- occurs in children under 2
- no seasonality
Aetiology
- microbio
- > HHV-6 most common
- > enterovirus
- > adenovirus
- > parainfluenza virus
- spread
- > most cases sporadic
- HHV-6 spread
- > almost all adults seropositive
- > spread most likely mother-infant saliva
Pathophys
- incubation period up to 10 days
- shedding is lifelong
- viral DNA incorporated into host genome
7
Q
Neonatal HSV background
A
Epidemiology
-approx 1/10,000
Aetiology
- HSV 1 and 2
- > poorer outcome with HSV-2
- > can each cause all modes of presentations
Pathophys
- pre-natal (rare)
- > primary infection
- > viraemia
- > transplacental spread
- peri-natal (most common)
- > retrograde spread through ruptured membranes
- > increased duration of ruptured membranes
- > symptomatic/asymptomatic mother
- > primary/recurrent disease
- > caesarian/vaginal delivery
- post natal
- > close contact with infected individual
8
Q
Roseola infantum evaluation and management
A
Hx
- Febrile phase
- > previously well
- > sudden onset high fevers for 3-4 days
- > coryza/cough/conjunctivitis
- > other wise well
- Rash phase
- > appears as fever disappears
- > starts on neck/trunk spread to face/extremities
- > non pruritus
- > doesn’t blister
- > lasts two days
Exam
- Vitals
- > may be febrile
- Rash
- > erythematous
- > maculopapular
- > blanchable
- Mouth
- > similar rash on palate (nagayama spots)
Management
- Supportive treatment
- > paracetamol
- > NSAIDs
- > hydration
- Prevention
- > virtually impossible for HHV-6
- > basic hand hygiene for other aetiologies
9
Q
Slapped cheek evaluation and management
A
Hx
- Low grade fever
- Flu like illness
- Arthralgia/arthritis
- Rash
- > facial appears first
- > feels burning hot
- > followed by limbs +- trunk
- > worse when warm
- Background
- > haemoglobinopathy (aplastic crisis)
- > pregnant women (miscarriage + congenital defects)
Exam
- Facial
- > erythematous
- > macular
- > sparing of nasal ridge + peri-orbital
- Limbs
- > maculopapular
- > lacy
- > erythematous
Management
- Supportive
- > paracetamol
- > NSAIDs
- > hydration
- Can persist for over 1 month
- Avoid pregnant women
10
Q
Rubella background
A
Epidemiology
-uncommon under 5
Aetiology
- Rubella virus
- Humans only known source
Pathophys
- lifelong immunity
- vaccine 97% effective
- spread
- > nasopharyngeal droplets
- shedding
- > 2 weeks before rash
- > contagious for over 1 year
- incubation
- > 2 weeks
- > haematgogenous spread (to fetus)
- complication
- > neutropenia
- > encephalitis
11
Q
Rubella evaluation and management
A
Hx
- Rash
- > begins on face and spreads to hands and feet
- > pruritic
- > made worse by heat
- > lasts for 4 days
- Fever
- Flu like illness
- Arthralgia/arthritis
- Lymphadenopathy
- > posterior auricular
- > posterior cervical
- > occipital
- Conjunctivitis
- > non purulent
Exam
- Rash
- > erythematous
- > discrete
- > maculopapular
- > may be petechial
- Palate
- > may have rash
Investigations
- Should be confirmed
- IgM
- > appears at clinical onset
- > lasts for months
- Confirm with convalescent IgG
- FBC
- > neutropenia
Management
- Supportive
- > NSAIDs
- > paracetamol
- > hydration
- Prevention
- > infections for up to 1 year
- > avoid pregnant women
12
Q
Impetigo background
A
Epidemiology
- Less common with age
- Non bullous
- > any age group
- Bullous
- > newborns
- Risk factors
- > over crowding
- > poor hygeine
- > malnutrition
Aetiology
- Staph aureus
- > MRSA in non bullous
- Strep pyogenes
- > non bullous
Pathohys
- Spread
- > highly infectious through fomites
- > breaks in skin (scabies/bites)
- Bullous
- > staph releases exotoxin
- > causes skin layers to split
13
Q
Impetigo evaluation and management
A
Hx
- Usually asymptomatic
- May be pruiritic
- History of infected contact
Exam
- Peri-oral + peri-nasal
- Vesicles
- > transient and seldom seen
- Crust
- > golden yellow
- > on erythematous base
- Bullae
- > initially clear then become turbid
- Cellulitis
- > severe MRSA
Management
- Neonate non-bullous
- > oral erythromycin
- Neonate bullous
- > IV clindamyin
- Non neonatal limited
- > topical bactroban
- Non neonatal widespread
- > oral flucloxacillin
- Supportive
- > twice daily washing with soap and water
14
Q
Scabies background
A
Epidemiology
-High prevalence in ATSI
Aetiology
- Ectoparasite
- > sarcoptes scabiei
Pathophys
- Tunnels into epidermis
- Lays multiple eggs daily
- > hatch in 2 days
- > adult in 2 weeks
- Spread
- > direct and prolonged skin-skin contact
- > shared clothing/bedding
- > sexual
- Fomites
- > survival for 2 days
15
Q
Scabies evaluation and management
A
Hx
- Pruritus
- > worse at night
- Known contact
Exam
- Linear lesions
- Papules or nodules
- > interdigital webs
- > penis
- Ink burrow test
- > marker pen on tract
- > wipe away with alcohol
- > reveal linear burrow
Investigations
- Scrapings
- > any lesion
- > multiple scrapings
- > sufficient to cause bleeding
- Dermatoscopy
Management
- Permethrin topical
- > apply from neck to soles of feet
- > wash off after 8 hrs
- > repeat after 2 weeks
- Antihistamines +- corticosteroid cream
- Prevention
- > treat all household/sexual contacts
- > wash clothing/bedding at high temperature
- > dry in sun or dryer
- > avoid school for 24hrs of treatment
