Dermatology Flashcards
Which organism most often causes bullous impetigo?
Staph aureus
How is bullous impetigo treated?
Systemic abx - flucloxacillin
What are the ocular signs of albinism?
Failure to develop a fixation reflex
Pendular nystagmus
Photophobia causing frowning
Is the AD or AR form of epidermolysis bullosa more severe?
AR form
When does infantile seborrhoeic dermatitis present?
First 3 months life
How is mild seborrhoeic dermatitis treated?
Emollients
How is more persistent or severe seborrhoeic dermatitis treated?
Sulphur and salicylic acid ointment for scaling
Mild corticosteroid +/- antibacterial and antifungal agents
What 2 commonest pathogenic organisms can cause secondary infection in atopic eczema?
Staph aureus
HSV
What percentage of children with atopic eczema has settled by age 16?
75%
What percentage of children with atopic eczema has settled by age 12?
50%
How are viral warts on hands or feet typically treated?
Salicyclic acid and lactic acid paint or glutaldehyde 10% lotion
Cryotherapy in older children
What does the typical lesion in molluscum contageosum look like?
small, skin-coloured pearly papules with central umbilication
How does tinea capitis usually present?
Scaling and patchy alopecia with broken hairs
Woods light may reveal bright green/yellow fluorescence
Where do scabies lesions typically occur in older children?
Finger and toe webs, flexor aspects of wrists, belt line, around nipples, penis and buttocks
Where do scabies lesions typically occur in younger children?
Palms and soles
What is the treatment of scabies?
Permethrin cream 5% below the neck, left on for 8-12hours then washed off
Face and scalp included in infants
OR
Benzyl benzoate 25% left on for 12hours then washed off#
OR
Malathion lotion 0.5% left on for 12hours
How is head lice treated?
Dimeticone 4% or malathion 0.5% applied into scalp and left overnight, then hair shampooed following morning
Repeated 1 week later
Wet combing every 2-3days for 2 weeks
What does guttate psoriasis appear as?
raindrop like lesions which are scaly and on trunk and upper limbs
In which condition does a ‘Christmas tree’ rash occur?
Pityriasis Rosea
What is pediculosis capitis?
Headlice
At what age does the embryonic epidermis begin to stratify?
8 weeks
In which condition does a herald patch occur?
Pityriasis Rosea
Which condition has exclamation mark hairs?
Alopecia
What type of collagen is affected in Ehlers-Danlos syndrome?
Type V collagen
Which gene mutations are associated with classical Ehlers-Danlos syndrome?
COL5A1 and COL5A2
What is type I collagen used for?
Bone construction
What does type 2 collagen do?
Main component of cartiledge
What condition is associated with defects in collagen I?
Osteogenesis imperfecta
What conditions are associated with defects in type II collagen?
Achondroplasia and Stickler syndrome
What conditions are associated with defects in type III collagen?
Vascular type EDS
What does type IV collagen normally do?
Forms basal lamina
What conditions are associated with defects in type IV collagen?
Alport syndrome
Goodpasture syndrome
Keloid scars are associated with and excess of what type of cell?
Fibroblasts
At what age does keratinisation occur in the fetus?
19 weeks
How does a fixed drug eruption typically present?
Well demarcated, round or oval, hyperpigmented macules or plaques that recur around the same site upon re-exposure to a drug
What is the mechanism of action of cyproterone acetate?
Inhibition of 17-alpha-hydroxylase thus reducing androgen production
How does Gianotti-Crosti syndrome typically present?
Characteristic pattern of rash on thighs, buttocks, upper arm and cheeks following a URTI.
Rash typically erythematous and papular in nature
What is the typical rash associated with neonatal SLE?
Erythematous, papulosquamous rash with fine scales and central clearing
What are the typical features of Bloom syndrome?
Growth retardation
Photosensitivity
Pigment abnormalities
Telangiectasia
How is Bloom syndrome inherited?
AR pattern
Which cancers does Bloom syndrome predispose to?
Leukaemia and Lymphoma
What does tumour-supression gene TSC1 encode?
Hamartin
What infections can lead to SJS most commonly?
HSV
Mycoplasma pneumoniae
Which layer of the skin does vitiligo affect?
Epidermis
Which enzyme is affected in Sjogren-Larsson syndrome?
Fatty aldehyde dehydrogenase
Which drugs are known to predispose to SJS?
Penicillins
Barbiturates
Phenytoin
OCP
Which immunoglobulin is most typically seen on immunofluorescence in bullous pemphigoid?
IgG4
What type of cell is present within peribulbar infiltrate in alopecia areata?
T cells - these reject the hair leading to hair loss
In what trimester does the skin become morphologically similar to adult skin?
Mid 3rd trimester
At what age does skin gain full barrier function?
Few weeks post delivery
Which skin layer are melanocytes derived from?
Ectoderm
What route do melanocytes take to reach the epidermis?
Migration from neural tube
What causes congenital dermal melanocytosis?
Failure of melanocytes to reach their proper epidermal location by birth - they remain trapped in the dermal layer
What are Blaschko’s lines?
Represents migrational patterns of epidermal cells during development and represent a manifestation of cutaneous mosaicism
What is cutaneous mosaicism?
Occurs when 2 or more genetically different populations of cells exist side by side within the skin
What typical patterns does cutaneous mosaicism follow?
V-shaped on upper spine
S-shaped on abdomen
Linear on arms and legs
Spiral on the scalp
Vertical in midface
What causes an epidermal naevus?
Ectoderm defect leading to overgrowth of epidermal keratinocytes
How does an epidermal naevus present?
At birth or early infancy
Localised, linear, warty, hyperpigmented plaque
How does hypomelanosis of Ito present?
Hypopigmented streaks which follow Blaschko’s lines
Which gene defect causes incontinentia pigmenti?
NEMO gene
How does incontinentia pigmenti present?
In the newborn with blisters that follow Blaschko’s lines which resolve and reveal hyperkeratotic, warty plaques. followed by increased pigmentation at 2-6months of age.
These later fade into atrophic, hypopigmented streaks
What type of extracutaneous manifestations are associated with epidermal naevus, incontinentia pigmenti and hypomelanosis of Ito?
CNS, heart, eye, skeletal system and dentition defects
What type of extracutaneous manifestations are associated with McCune-Albright syndrome?
Bone and hormonal abnormalities
What type of extracutaneous manifestations are associated with focal dermal hypoplasia?
Eye, MSK, renal, GI, cardiac and neurological abnormalities
What is a collodion baby?
Baby born encased in a taut, shiny, transparent membrane that is formed by aberrant stratum corneum
In colloid baby - what phenotype does this most often progress to?
Ichthyosis
Embryologically where does the dermis of the face and anterior scalp derived from?
Neural crest ectoderm
Embryologically where does the dermis of the trunk and extremities derived from?
Mesoderm
At what gestational age are dermal fibroblasts developed?
6-8weeks
What is the role of dermal fibroblasts in early fetal development?
Synthesising collagens and microfibrillar components
At what age is the dermis noted to be in the papillary and reticular components?
12-15weeks GA
What is the role of the dermal-epidermal junction?
Adhesion between basal keratinocytes and dermis
Resistance against shearing forces on the skin
What is thought to cause strawberry birthmarks?
Proliferation of endothelial cells and mutations in genes which encode VEGF
What are the cutaneous features of tuberous sclerosis?
Ash-leaf macules
Adenoma sebaceum
Fibromatous nodules
Periungual fibromas
Shagreen patches
What can mutations in genes which encode the dermal-epidermal junction cause?
Skin fragility and blister formation
How long do infantile haemangiomas proliferate over?
6-9months
What is the first line treatment for infantile haemangioma (assuming treatment is advised)?
Oral propranolol
(More recently topical B-blockers may also be effective)
In what circumstances should treatment be considered for infantile haemangiomas?
Large with potential for disfigurement, ulceration or impairment of normal functions
How are beta blockers thought to help with infantile haemangiomas?
Inhibition of angiogenesis and recruitment of endothelial progenitor cells as well as inducing apoptosis.
Genetic mutations in what type of cell can lead to neurocutaneous syndromes?
Neural crest cells
How is tuberous sclerosis inherited?
AD - although 50% are new mutations
What structures are formed from the ectoderm?
Skin
Nails
Sweat glands
Teeth
How is NF inherited?
AD
What are the neurological features of tuberous sclerosis?
Seizures
Cognitive impairment
What are the layers of the epidermis?
Stratum corneum
Stratum lucidium (only on palms and soles)
Stratum granulosum
Stratum spinosum
Stratum basale
What are the cutaneous features of NF?
Cafe-au-lait patches
Dermal neurofibromas
What are the cutaneous features of Sturge-Weber syndrome?
Port-wine stain on eye or forehead areas
How is Sturge Weber syndrome inherited?
AD
What is the mechanism of action of phototherapy?
Targets inflammatory cells, alters cytokine production and has an antimicrobial effect.
How does chronic bullous disease of childhood present?
Children >3y/o with small tense blisters on an erythematous background.
Lesions affect perianal area and spread to trunk, thighs, limbs, hands and feet.
May also be mucosal involvement
