Dermatology Flashcards
1
Q
ddx for purpura
A
Common (STD)
- Septicaemia
- > mainly meningococcus
- > varicella
- > GAS
- > pneumococcal
- Trauma (most common)
- > intentional
- > unintentional
- Drugs
- > sulfur containing
- > antibiotics
- > anti-convulsants
Disorders of vessel wall (Sick Vessels Can Haemorrhage)
- Steroids/cushings
- Vasculitis
- Collagen
- > Ehlers, marfans, scurvy
- Henloch Shonlein Purpura
Platelet disorders (I’M FluID)
- Immune thrombocytopaenia
- Microangiopathic haemolytic anaemias
- > HUS
- > TTP
- > DIC
- Functional defects due to
- > liver disease
- > uraemia
- Inherited diseases
- > Bernard Soulier
- Dysproteinaemias and myeloproliferative disorders
Von Willebrand disease
Coagulation disorders
- Haemophilia
- > A, B and acquried
- Factor XI deficiency
- Vitamin K
- > deficiency
- > enzyme disorder
- Liver disease
2
Q
urticaria overview
A
Epidemiology
-affects approx 20% of population
Aetiology
- bacterial/viral infection (most common cause in kids)
- > picornaviruses
- > respiratory viruses
- > mycoplasma pneumoniae
- > Hep A and B
- allergic reaction (type 1 hypersensitivity)
- direct mast cell activation
- > opioids
- > vancomycin
- > contrast
- > tomatoes and strawberries (kids)
- NSAIDs (non-selective)
- histamine poisoning (scombroid syndrome)
Pathophys
- vasodilation/increased permeability
- > release of histamine from mast cells in dermis
- > exogenous histamine
- > inflammation/infection
Clinical manifestations
- erythematous plaques
- intensely pruritic
- rash changes rapidly/individual lesions resolve in 24hrs
Treatment
-H1 anti histamines
3
Q
Angioedema overview
A
Epidemiology
- common allergic presentation
- more common in africans
Aetiology
- mast cell/histamine mediated
- > same aetiologies as urticaria
- bradykinin mediated
- > ACEI
- > rare enzyme deficiencies
- idiopathic
- > calcium channel blockers
- > herbal medications
Pathophys
-increased permeability of capillaries
Clinical manifestations
- asymmetrical oedema of non-gravity dependent sites
- differentiated histamine/bradykinin mediated
- > histamine mediated = pruritis/urticaria
- swollen lips, tongue and uvula
- larynx
- > altered voice
- > difficulty swallowing
- skin and mucosa
- > resembles cellulitis but less painful
- bowel wall
- > colicky abdo pain
Treatment
- histamine mediated
- > H1 antagonist
- > glucocorticoids
- badykinin mediated
- > cease ACEI
4
Q
Measles overview
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
- children of vaccinated mothers
- > lower plancental transfer of antibodies
- > higher rates of infections <12mths
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
Clinical manifestations
- incubation period
- > asymptomatic
- prodome
- > lasts up to 1 week
- > fever, mailaise, anorexia
- > coryza, conjunctivitis, cough
- enanthum (koplick spots)
- > appear during prodrome/before exanthum
- > white/blue/grey papules
- > erythematous base
- > buccal, inside lips, palate
- exanthemous phase
- > lymphadenopathy
- > pharyngitis
- > worsening resp symptoms
- > rash
- erythematous maculopapular rash
- > spreads cephalocaudally
- > transitions from blanching to non blanching
- > coalesces
- > spares hands and feet
- complications
- > leukopenia and immunocompromise
- > diarrhoea
- > pneumonia
- > encephalitis
Treatment
- supportive
- vitamin A supplementation
5
Q
Parvovirus B19 infection
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 athralgia
- > due to immune complex disease
Clinical manifestations
- prodome of up to 1 week
- > viraemia
- > flu like illness
- > possibly anaemia
- > contagious
- seroconversion
- > majority asymptomatic
- > arthritis
- > erythema infectiosum
- > not contagious
- erythema infectiosum (fifth disease/slapped cheek)
- > more common in children
- > first fever, mailaise, coryza, nausea, diarrhoea
- > then erythematous malaria rash/cirumoral pallor
- > then lace-like erythematous rash on extremities
- > resolves in a week but may recur
- arthritis
- > polyarticular, symmetric, small joints
- > more common in adults
Complications
- transient aplastic crisis
- > ineffective erythropoiesis (underlying RBC disease)
- fetal infection
- > more susceptible (short RBC lifespan)
- > miscarriage/intrauterine death
- > non-immune hydrops fettles
Management
- clinical diagnosis
- supportive/symptomatic management
6
Q
Roseola infantum
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
Clinical manifestations
- febrile phase (up to 5 days)
- > high fever
- > appears otherwise well
- > coryza/conjunctivitis/cough/lymphadenopathy
- rash (up to 2 days)
- > appears after fever abates
- > may come and go quickly
- > maculopapular, blanching, non pruritic
- > starts on neck/trunk
- > spreads to face/extremities
Investigations (not required)
- leukocytosis/neutropenia
- HHV-6 serology
Management
- benign disease
- supportive treatment
- prevention
- > virtually impossible for HHV-6
- > basic hand hygiene for other aetiologies
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
Neonatal HSV investigations
A
Formal ophthalmological exam
Urinalysis
Blood
- PCR
- > confirms diagnosis
- culture
- > bacterial infection ddx
- FBC
- LFTs
- EUCs
Surface swab
- conjunctiva/mouth/rectum + lesions
- viral culture
- > highest sensitivity/specificity
CSF
- PCR
- > highest sensitivity/specificity
- culture
- > bacterial infection ddx
- biochemical findings
- > mononuclear pleocytosis
- > low glucose
- > raised protein
EEG
-highly sensitive for CNS involvement
Neuroimaging
- MRI or CT with contrast
- findings
- > parenchymal oedema
- > haemorrhage
- > destructive lesions
9
Q
Neonatal HSV syndromes
A
Pre-natal manifestations
- in-utero
- > placental infarcts
- > inflamed umbilicus and placenta
- > hydrops fetalis and in utero demise
- survivors
- > skin vesicles/ulceration/scarring
- > eye damage
- > microcephaly/hydranencephaly
Skin, eye and mouth disease
- usually presents within 2 weeks
- skin
- > clustered/coalescing vesicles w erythematous base
- > lesions present where skin is traumatised
- eyes
- > initially watery/conjunctival erythema
- > keratoconjunctivitis
- > progresses to cataracts/chorioretinitis and blindness
- mouth
- > ulceration of gingiva and oral mucosa
- > peri-oral vesicles
- may progress to CNS or disseminated disease
CNS disease
- majority
- > present within 2 weeks
- > have skin findings
- spread
- > nasopharyngeal infection and olfactory nerves
- > haematogenous in disseminated disease
- presents with meningitis picture
Disseminated disease
- presents in first 2 weeks
- sepsis presentation
- affects any organ system
- mortality rate >80% if untreated
10
Q
Neonatal HSV management
A
Supportive and expectant management
- > shock and sepsis
- > glucose and electrolytes
- > seizures
- > DIC
- > secondary bacterial infection
Antiviral treatment
- high dose acyclovir IV
- > SEM = 14 days, CNS/disseminated = 21
- topical ganciclovir for eye disease
Follow up
- > formal neurodevelopment testing
- > audiology
- > ophthalmology
Prognosis
- disseminated = 1 year mortality 30%
- CNS = 1 year mortality 2%
- SEM = mortality is rare
- cutaneous recurrence is common
