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A chronic, relapsing and remitting scaling skin disease
What is the pathogenesis of psoriasis?
- T-cell mediated autoimmunity
- Abnormal T cell infiltration releases cytokines = increased keratinocyte proliferation
What are some co-morbidities of psoriasis?
- Psoriatic arthritis: Arthritis in 30% of chronic psoriasis
- Metabolic syndrome
- Liver disease
What are the frequent ages of onset of psoriasis?
Between 20-30 and 50-60
Outline the common clinical presentation of psoriasis
- Discrete, circular, pink patches/plaques from hyperkeratosis
- Found on extensor surfaces, scalp, buttocks (trauma sites)
- Nail features; onycholysis, pitting
Describe the subtypes of psoriasis
- Plaque: Pink/red scaly plaques
- Guttate: 'Raindrop' like, very small, circular plaques on trunk. Related to strep throat
- Pustular: Diffuse redness with blisters on palms and feet soles + exfoliation
- Erythromdermic: Generalised redness, extreme keratosis
What factors affect the treatment choice for psoriasis?
- Patient choice
- Patient capability
- Related arthropathy
Outline the treatment choices for psoriasis
- Topical creams
- (in order of toxicity)
Outline the pathophysiology of eczema
- Inherited abnormalities in the skin; irregular fillagrin expression
- Creates a 'barrier defect'
- Increased permeability reduces antimicrobial function
Describe some endogenous causes of eczema?
- Atopic: Allergy = itchines. Managed with moisturisers + antihistamines, maybe topical steroids
- Seberrhoiec: Yeast infection; anti-fungal shampoo and moisturiser given
- Varicose: Vein incompetence = hydrostatic pressure = stretched dry skin. Compression socks
What are common causes of exogenous eczema?
- Contact allergies the main cause; nickel, chromate, cobalt, fragrance etc.
- Photosensitivity due to drugs
What is native joint septis arthritis?
- A medical emergency, where one of the patient's joints becomes infected.
- Loss of cartilage and osteoarthritis
What is the clinical presentation of septic arthritis?
- Single or polyarticular
- Knee and hip
- Can develop into severe sepsis and septic shock
What investigations are useful in septic arthritis?
- Joint aspirate: gram stain, microscopy for crystals (gout) and cultures
- Blood cultures: colony and sensitivity testing
- Imaging: in osteomyelitis
Outline some causative organisms of septic arthritis
- S. Aureus
- Strep pyogenes, pneumococcus
- H. Influenzae
- N. Meningitidis/gonorrhoeae
How is septic arthritis treated?
- Minimum of two weeks IV antibiotics
- Afterwards, 3 weeks oral antibiotics
What is the definition of osteoarthritis?
Progressive infection of bone, characterised by necrosis and sequestra formation
Outline the causes of oseoarthritis
- Similar organisms to septic arthritis
- Haematogenous spread
- Local spread from overlying infection (e.g. cellulitic ulcer)
- Trauma (compound fracture)
- Surgical inoculation
How is osteoarthritis investigated and treated?
- MRI the image of choice
- Antibiotic choice depends on culture; eithe oral or 4-6 weeks IV
Outline the use of surgery in osteomyelitis
- Debulk infection back to healthy bone
- Manage dead space that remains
- Stabilise infected fractures
- Debride sinuses
- Close wounds
Outline the pathogenesis of prosthetic joint infections
- Usually caused by coagulase negative Staph aureus; gram negative bacilli, S. Viridans.
- In local spread, it may be anything
- Prosthesis has no blood supply, so infections common
- Biofilms common
How are infections commonly introduced in prosthetic joint infections?
- Local spread in 60-80%; skin organisms
- Haematogenous in 20-40%
Outline the clinical presentation of prosthetic joint infections
- Inflammation; pain, effusion, warmth
- Fever and systemic symptoms
- Loosening on radiograph/mechanical dysfunction
What investigations are used in prosthetic joint infections?
- Macroscopic appearance, histopathology and microbiology
- Cultures are not definitive due to contamination
- Tissue, fluid or pus samples preferable to swabs
What prophylaxis is commonly used in preventing PJIs?
- Given 30mins before incision, for <24 hours
- Cephalosporins used, unless C.Diff present
- If MRSA, glycopeptides used (vanco or teico)
What treatments are used in PJIs?
- DAIR: Debride, antibiotics and implant retained
- Removal: If infection >30 days after surgery, joint may not be functional. Prosthesis/cement removed
Give the definition of:
- Resection arthroplasty
- Revision arthroplasty
- Pseudo arthrosis
- Putting in an artificial joint
- Replacing a diseased joint with an artificial one
- Re-operating on an artificial joint
- Fusing two bones together
- Allowing two bones to articulate, without a joint
- Spreading infection of the dermis and subcutaenous tissue
- Often affects lower limb
Outline the clinical presentation of cellulitis
- Spreading, diffuse edge
- Often painless
- Systemic symptoms in 40% (fever, nausea)
Outline the diagnosis of cellulitis
- Usually clinical, not laboratory
- If below the waist or in diabetis, expect gram negative
- In IVDUs, it can be anything
Outline the management of cellulitis
- Antibiotics: Flucloxacilllin, penicillin V (clinda/vanco if allergy)
- Mark area of inflammation to monitor progress
- If refractory, consider; resistance/admission/underlying condition/incorrect diagnosis (e.g. DVT, erysipelas)
- Streptococcus infection of dermis, especially face and eyes
- Similar to cellulitis
- Well demarcated edge, raised
Describe impetigo, including treatment
- Staph infection of epidermis
- Often peri-oral, honey coloured skin crusting
- Very transmissible
- Gentle crust removal, flucloxacillin
Describe methods of reducing surgical infection likelihood
- MRSA screening
- Hair removal
- Prophylactic antibiotics
- Glucose control
Define necrotising fasciitis
Rapidly spreading infection of subcutaneous fascia, occurs over hours
Outline the pathophysiology of necrotising fasciitis
- Toxin or mixed mediated
- Toxins a superantigen; cytokines released + toxic shock syndrome
- Medical emergency; 70% mortality if untreated
What are the characteristics of necrotising fasciitis?
- Intitially painful, becomes painless in later stages
- Dark bullae
- Very rapid spread of dusty, necrotis skin
- Systemic upset
- Skin crepitus can occur, due to air entry into subcutaneous tissue
How is necrotising fasciitis treated?
- Rapid surgical assessement and debridement of all necrotic tissue
- Tissue samples sent from theatre for cultures and sensitivity
- Broad IV antibiotics cover helpful; penicillin, fluclox, clinda, metro, genta
Describe the cause, presentation and treatment of abscesses
- Causes include IVDU, trauma
- Presents with pain, swelling
- Aspirated and cultured
How are burns managed?
- Cultures rarely sterile, due to rapid colonisation
- Topical antimicrobials
- Topical antibiotics
- Systemic antibiotics