Week 2 Flashcards
What are the two types of fascia and how do they differ?
Superficial fascia, made up of loose connective tissue and fat
Deep fascia - a tough sheet, dividing regions into compartments
Describe the arterial supply of the upper limb, proximal to distal
Subclavian artery -> axillary artery -> brachial artery -> SPLIT into radial artery and ulnar artery, which give off the deep and superficial palmar arteries respectively (although both these arteries contribute to each palmar arch)
Describe the venous blood supply of the upper limb, distally to proximally
Palmar venous arches drain into the Radial and Ulnar veins, which both drain into the Brachial vein
Dorsal venous network drains into the cephalic and basilic veins. These two are linked in the antecubital fossa by the Median cubital vein.
The Cephalic vein drains into the Axillary vein, and the Basilic vein joins with the Brachial vein to form the Axillary vein.
The Axillary vein then goes on to drain into the Subclavian vein
How do venous ulcers occur?
Where is the most common site?
Immobility/venous valve failure of any cause leads to chronic venous insufficiency, which as well as resulting in deep venous stasis also results in superficial microcirculatory deficiencies = ulcers form
Most common site of venous ulceraction is the “gaiter area” - medial aspect of the distal leg
What are some of the chemical mediators of itch in the skin?
Histamine
PGE2
Acetylcholine
Serotonin
Kallikrein
IL-2
What are the four categories of causes of itch?
Pruritoceptive - something in the skin triggers the itch, associated with inflammation or dryness
Neuropathic - damage of any sort to central or peripheral nerves
Neurogenic - no evident damage in the CNS, but itch is caused by effects on CNS receptors
Psychogenic - psychological cause with no damage to the CNS e.g. itch is a delusion of infestation
Systemic diseases associated with itch mostly are neurogenic causes of pruritus. Give some examples
Haematological
Paraneoplastic
Liver and bile duct
Psychogenic disease
Kidney disease
Thyroid disease
What are some of the treatments used in the management of itch?
Sedative anti-histamines
Emollients
Antidepressants
Phototherapy
Opiate antagonists e.g. ondansetron
(if neuropathic, anti-epileptics)
Where are melanocytes found? What is their function?
At the DE junction, in the basal layer
Melanocytes synthesise melanin, and transfer the pigment to keratinocytes via dendritic processes
What type of collagen makes up the dermis?
Matrix of Type I and Type 111 collagen fibres
What do the following terms mean:
Parakeratosis
Hyperkeratosis
Acanthosis
Papillomatosis
Spongiosis?
Parakeratosis - peristence of nuclei in the keratin layer
Hyperkeratosis - increased thickness of keratin layer
Acanthosis - increased thickness of whole epithelium
Papillomatosis - irregular epithelial thickening
Spongiosis - oedema fluid between squames appears to increase prominence of intercellular prickles
Give a brief definition of Psoriasis
Common chronic inflammatory dermatosis
Epidermal hyperplasia, meaning increased epithelial turnover
Pathogenesis remains elusive
Causes red, flaky, crusty patches with scale
Found commonly on extensor surfaces (knees, elbows, scalp, lower back) but can appear anywhere on the body
Lichenoid disorders are characterised by damage to the basal layer of the epidermis. What is the most common form of this disorder and how does it present?
Lichen planus
Presents with irregular sawtooth acanthosis and basal damage with the appearance of cytoid bodies
Inflammatory condition that can affect skin, hair, nails and mucous membranes. If affecting the skin, Lichen Planus appears as purplish, often itchy, flat-topped bumps appearing over several weeks
How do immunobullous disorders primarily present? What are some important examples?
Blisters are the primary feature
Important examples:
- pemphigus
- bullous pemphigoid
- dermatitis herpetiformis
Give a brief definition of pemphigus.
What is the most common type?
Rare autoimmune bullous disease
Loss of integrity of epidermal adhesion - affects the DEJ
Variable severity (occasionally fatal), and responds to steroids
Like in other lichenoid disorders, the mucosa of the mouth and respiratory tract may be affected, which in some cases can prove to be fatal.
4 subtypes which are distinguished clinically and histologically. Most common type is Pemphigus vulgaris
In pemphigus vulgaris, what do the auto-antibodies target? What type of immunoglobulin are they? What does this result in?
IgG autoantibodies are made against desmoglein-3
DG-3 maintains desmosomal attachments. Immune complexes form on the cell surface, resulting in complement activation and protease release and subsequent disruption of desmosomes.
The end result is acantholysis (loss of intercellular connections, this is absent in bullous pemphigoid) and the appearance of shallow lesions
In contrast to pemphigus vulgaris, what do the autoantibodies target in Bullous Pemphigoid? How does this present?
Autoantibodies target the hemidesmosomes and basement membrane
This results in local complement activation and tissue damage, and the formation of subepidermal blisters
There is no evidence of acantholysis
When suspecting Bullous Pemphigoid, why is it better to send early lesions for histological analysis, rather than older ones?
Older lesions of pemphigoid show re-epithelialisation of their floor, mimicking pemphigus vulgaris
Give a brief description of dermatitis herpetiformis. What is the hallmark symptom?
What HLA haplotype is it associated with, and what other autoimmune condition does it have a strong association with?
Relatively rare autoimmune bullous disease
Results in intensly itchy symmetrical lesions on the elbows, knees and buttocks. Hallmark symptom is papillary dermal microabscesses, often excoriated.
Associated with HLA-DQ2
Strongly associated with Coeliac disease
What sensitivity do 90% of people with dermatitis herpetiformis have?
What type of immunoglobulins feature in DH and what do they target?
Gluten sensitivity enteropathy
IgA anitbodies target the gliadin component of gluten, but also cross react with connective tissue matrix proteins
Briefly, how does Acne (acne vulgaris) occur, and where does it commonly present?
Increased androgens at puberty, and possible increased androgen sensitivity of sebaceous glands?
Keratin plugs up the pilo-sebaceous unit, which then become infected with the anaerobic bacterium Corynebacterium acnes as they cannot clear the microorganism
Commonly presents in sites with increased sebaceous activity - face, upper back, upper chest etc.
Give a brief description of Rosacea
Common, 10% prevalence in caucasian adults
More common in females
Presents with recurrent facial flushing, visible blood vessels, pustules and thickening of the skin (rhinophyma)
Unlike acne, there are no blackheads/whiteheads (comedones)
Aggrivated by a range of triggers, including…
- sunlight
- alcohol
- spicy foods
- stress
- tetracyclines in some (?)
Name some competitive bacterial flora
- Staphylococcus epidermidis*
- Corynebacterium sp.*
- Propionibacterium sp.*
What test is used to differentiate between Staph aureus and other forms of Staph?
The coagulase test
Staph aureus is coagulase positive and gives off a golden colour
All other forms of Staph are coagulase negative
- Staphylococcus* appear as chains/clusters
- Streptococcus* appear as chains/clusters
Strep = chains
Staph = clusters
How is Streptococcus sub-divided? What are the sub-groups?
Based on haemolysis
Alpha haemolysis - Strep. pneumoniae (pneumonia), Strep. viridans (commensal, endocarditis)
Beta haemolysis - Group A Strep (throat, skin infections), Group B Strep (neonatal meningitis), Group C, G
Non-haemolytic - Enterococcus (gut commensal)
What is the antibiotic of choice for treating a Staph aureus infection?
FLUCLOXACILLIN!!!
Some strains of Staph aureus produce toxins - name some of these toxins
Enterotoxin
PVL
SSSST
What would you use to treat Methicillin-Resistant Staph. aureus?
Not fluclox!
Doxycycline
Co-trimoxazole
Clindamycin
Vancomycin
What bacterium may cause infection in prosthetic implants? E.g. artificial joints, heart valves IV catheters etc.
Staph. epidermidis
Name one of the toxins produced by Beta-haemolytic Strep. that damages tissue
Beta-haemolytic Strep.
Haemolysin is produced.
What are the two most important members of the alpha-haemolytic Strep group?
Strep. pneumoniae - most common cause of pneumonia
Strep. viridans - commensal, associated with endocarditis
Strep. pyogenes is a Group A beta-haemolytic Strep. Name some of the conditions it can cause.
What is the treatment?
Infected eczema
Impetigo
Cellulitis (and Erysipelas)
Necrotising fasciitis
Treatment is with penicillin, as with Staph (Flucloxacillin can be used here too!)
If Necrotising fasciitis, urgent surgical debridement is also required
What are the two types of Necrotising fasciitis?
Type I - mixed anaerobes and coliforms, usually occurs following abdominal surgery
Type II - caused by Group A Strep
When would you swab a leg ulcer?
Only if there are signs of cellulitis or infection. Leg ulcers are usually due to a vascular issue
What fungal infection is ‘Tinea’ the name for? Where are the following…
- Tinea capitis
- Tinea barbae
- Tinea manuum
- Tinea unguium
- Tinea cruris?
Tinea = ringworm
Capitis = scalp
Barbae = beard
Manuum = hand
Unguium = nails
Cruris = groin
What are the 3 most common causal organisms of ringworm infection? (Dermatophytes)
How is infection diagnosed?
- Trychophyton rubrum* - by far the most common, roughly 70%
- Trychophyton mentagraphytes*
- Microsporum canis*
Diagnosed by taking a skin scraping and sending to the lab for culture and microscopy
How are Dermatophyte infections treated?
Small areas of skin/nails - Clotrimazole (Canestan) cream
Extensive skin infections/scalp infections - either Terbinafine or Itraconazole, both given orally
What is the causative organism in Scabies infections? What is the treatment?
Sarcoptes scabiei
Incubation period of up to 6 weeks and causes an intensly itchy rash affecting finger webs, wrists and genital area
Treatment - malathion lotion applied overnight, or benzyl benzoate
What is the fancy word for ‘lice’? What is the treatment?
Pediculus e.g. Pediculus capitis (head lice)
Treatment is Malathion lotion
Why can gram positive organisms survive in the environment?
Because of their cell walls
What is the causative organism of both chickenpox and shingles?
Varicella zoster
Varicella causes chickenpox
Herpes zoster causes shingles
What are some of the complications of chickenpox?
Secondary bacterial infection
Pneumonitis
Haemorrhagic complications
Encephalitis
Scarring
What are some of the features of Shingles?
Reactivation of the varicella zoster virus later in life
Follows a dermatomal distribution
Appears in the elderly and the immunocompromised
Progression goes tingling/pain > erythaema > vesicles > crusts
Pain increases with age, and is neuralgic in nature
If Shingles presents on the face and affects one of the eyes, what is the name given to this condition?
Opthalmic zoster - opthalmic branch of the trigeminal nerve is affected
What are the features of Ramsay-Hunt Syndrome?
Vesicles and pain in the auditory canal and throat
Facial palsy (CN VII)
Irritation of CNVIII - presents as deafness, tinnitus, or vertigo
Describe the pattern of disease of Herpes Simplex
Presents initially in pre-schoolers as extensive ulceration in and around the mouth. Lasts for about a week.
Can recur in later life with blistering around the mouth and can be spread.
Two types:
- HSV Type I, main cause of oral lesions and causes half of genital herpes. Can also cause encephalitis
- HSV Type II - rare cause of oral lesions, and can also cause genital herpes and encephalitis
What anti-viral drug can be used for both varicella zoster and herpes simplex? How does it work?
Aciclovir
Analogue of guanosine, is selectively taken up into viral DNA and inhibits replication.
Doesn’t eliminate latent virus
Briefly describe molluscum contagiosum.
How is it treated?
Causes the formation of fleshy, firm, pearlescent nodules
Self-limiting, but may take months to disappear
Common in children but can also be sexually transmitted
Can be treated with liquid nitrogen therapy
What virus causes warts? How is it treated?
What other diseases can this virus cause?
Human papilloma virus - self-limiting and uncomplicated, most commonly seen in children.
Treated with topical salicylic acid
Over 80 types of HPV, 1-4 are most common in warts/verrucas
Also causes genital warts - HPV 6 and 11
Associated with cervical cancer - HPV 16 and 18
Can also cause head and neck cancer
What is the other name for “slapped cheek” disease? What is the causative organism?
How else can this affect the body?
Erythema infectiosum
Caused by parvovirus B19
Can also cause acute arthritis, especially in the wrists
What animal is Orf associated with? Who gets it? Is it serious?
Orf is associated with sheep
Farmers, typically
No, self-limiting and constitutional symptoms are rare
Appears as a firm, fleshy nodule on the hand
What is the causative organism of syphilis? How is it transmitted and treated?
What are the three stages of presentation?
Treponema pallidum
Transmitted via sexual intercourse
Treated with a series of injections with penicillin
Primary stage - painless ulcer at site of entry
Secondary stage - red rash over body, prominent on soles of feet and palms
Tertiary - CNS, cardiovascular, gummatous etc. complications
Lyme Disease: causative organism, features at presentation and treatment
Organism - Borrelia burgdorferi
Features - erythema migrans (early), heart block, nerve palsies, arthritis (late)
Treatment - doxycycline or amoxicillin
Briefly describe the immunopathology of allergic contact dermatitis
Antigen is processed in the epidermis by Langerhan’s cells
Antigen is then presented to Th cells in the dermis, which migrate to nodes via the lymphatics
How is a contact allergy diagnosed?
Via patch testing
What is the difference between contact allergic dermatitis and irritant (contact) dermatitis? (kind of obvious…)
Irritant dermatitis is a non-specific reaction in response to physical irritation rather than a specific allergic reaction.
The two may be different to distinguish between, and may also co-exist
Give a brief description of eczema (atopic dermatitis).
What % of school children does it affect?
Ill-defined erythema and scaling
Generalised dry skin
Appears in areas of flexion
Associated with other atopic disease e.g. asthma, allergic rhinitis, food allergies etc.
Affects up to 25% of school-aged children
Secondary infection with eczema is common. If crusting appears, what organism is this indicative of?
Staph. aureus
What other secondary infection is associated with eczema and classically appears as monomorphic punched out lesions? (see picture)
Eczema herpeticum, caused by secondary infection with the Herpes Simplex Virus
The UK diagnostic criteria for eczema consists of itching plus 3 or more further features. Name some of these features
Visible flexural rash
History of flexural rash
Personal history of atopy
Generally dry skin
Onset before the age of 2
What treatment options are available for eczema?
Emollients
Avoidance of irritants (soaps, shower gels etc.)
Topical steroids
Treating secondary infections
Phototherapy - mainly UVB
Systemic immunosuppressants
(Biologic agents are also an option)
What causes atopic eczema? What has been identified as the most important genetic component?
Multiple genetic and environmental factors contribute to eczema development
Most important component is filaggrin, encoded for by thew FLG gene
What form of eczema is commonly mistaken for psoriasis? How are the two differentiated?
Discoid eczema
Eczema crucially does not form raised plaques, unlike psoriasis
Name the type of eczema
What is the clue?
Photosensitive eczema (Chronic Actinic Dermatitis)
Collar cut-off
What term is given to inherited genetic skin conidtions?
What common genetic skin condition may present as infantile seizures?
Genodermatoses
Tuberous sclerosis is a genodermatosis that may present as infantile seizures
What is the earliest cutaneous sign of tuberous sclerosis, pictured here?
Ash-leaf macule
Tuberous sclerosis is characterised by the formation of numerous benign tumours.
Where might these tumours present?
Peri-ungual fibromas - around nails
Facial angiofibromas - often misdiagnosed as acne
Cortical tubers and/or calcification of falx cerebri - tumours in the brain, may cause seizures
Hamartomas = angiomyolipomas which may present in the heart, lung or kidneys
Bone cysts
Mutations in what genes can result in tuberous sclerosis? What do these encode for?
What is the inheritance pattern?
Mutations in either TSC1 or TSC2
These encode for tuberin and hamartin
Autosomal dominant
