Infection and Immunology Flashcards
Define cellulitis and erysipelas
- Cellulitis is an acute bacterial infection of the dermis and subcutaneous tissue.
- Erysipelas is a superficial form, affecting the dermis. It is well demaracated, and sepsis is less likely
List risk factors of cellulitis
- Trauma, leg ulceration, maceration or eczema (break in the skin)
- Insect bites
- Lymphoedema
- Leg oedema
- Venous insufficiency and history of venous surgery
- Obesity
- Pregnancy
- Chicken pox
- Conditions that predispose infection (eg. diabetes)
- Neuropathy
- Alcohol misuse
- Recurrent - elderly, previous cellulitis, chronic lymphoedema
List common causative agents of cellulitis
- Strep pyogenes
- Staph aureus
Describe prevalence of cellulitis
- 0.2 per 1000 person years to 24.6 per 1000 person years
- Recurrence common
List symptoms of cellulitis
- Acute onset of red, painful, hot, swollen skin
- Spreads rapidly
- Fever, malaise, nausea, shivering, rigors
List signs of cellulitis
- Tender skin
- Obvious break in the skin where an organism may have entered
- Diffuse redness, well demarcated edge
- Blisters and bullae
- Inflamed lymph nodes or lymphangitis (presence of red, linear streaks spreading proximally from the area of cellulitis, peau d’orange appearance)
- Ulceration
Describe classification of cellulitis
- Class I — there are no signs of systemic toxicity and the person has no uncontrolled comorbidities.
- Class II — the person is either systemically unwell or systemically well but with a comorbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection.
- Class III — the person has significant systemic upset, such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable comorbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize.
- Class IV — the person has sepsis or a severe life-threatening infection, such as necrotizing fasciitis.
Describe investigations performed in cellulitis
- Swab for culture
- Ultrasonography (abscess, drainable fluid collection)
- Skin biopsy
- WBC, ESR, CRP
- If orbital, CT/MRI
Describe management of cellulitis
- Draw around the lesion and monitor
- Antibiotics (oral amox if possible, review IV after 48 hours to switch to oral, if MRSA trimethoprim-sulfamethoxazole)
- Hospital admission if class IV or III, rapidly deteriorating, young, immunocompromised, facial, or significant lymphoedema
- Referral if severely unwell, infection near eyes or nose, uncommon pathogen, lymphangitis, cannot take oral antibiotics, not responding to oral antibiotics)
- Recurrent episodes refer
List complications of cellulitis
Acute
- Necrotizing fasciitis (rapidly progressive, extensive gangrene and necrosis of skin and underlying structures)
- Myositis
- Sepsis
- Subcutaneous abscesses
- Post streptococcal nephritis
Chronic complications
- Persistent leg ulceration
- Lymphoedema
- Recurrent cellulitis
Describe prognosis of cellulitis
- Most cases resolve with treatment
- After 12 months, 29.4% of patients had at least 1 recurrence
- Length of hospitalization increases with each subsequent recurrence
Define anaphylaxis
A severe, generalised or systemic hypersensitivity reaction, characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes
Describe epidemiology of anaphylaxis
- Risen by 70% in the last 5 years
- Most commonly food allergic reactions in young children
- Affects both sexes equally
- 1/3 is food related
- Medicines are common causes in adults
List risk factors of anaphylaxis
- Less than 30 at risk of food and exercise related
- Atopy/ asthma
- History of anaphylaxis
- Exposure to a common sensitiser (eg. latex)
- Adults at risk of food, insect venom and medicine related
- Female sex more at risk of food-associated and exercise associated
List symptoms of anaphylaxis
- Acute onset
- Angiooedema (airway swelling, tongue)
- SOB
- Respiratory arrest
- Confusion
- Hives
- Pruritis
- Nausea, vomiting, diarrhoea, incontinence
- Abdominal cramps and pain
- Agitation, anxiety, sense of impending doom
List signs of anaphylaxis
- Inspiratory stridor and hoarse voice
- Chest hyperinflation, accessory muscle use, wheeze
- Cyanosis
- Pale clammy skin
- Hypotension
- Tachycardia
- Respiratory arrest
- Bradycardia
- Urticaria
- Erythema
List investigations for anaphylaxis
- Mast cell tryptase (16 years or over during or soon after resusitation, one as soon as possible, one 1-2 hours after symptoms, one 24 hours. May be elevated)
- Plasma histamine
- ECG (non-specific ST changes)
- Urea and electrolytes (normal)
- ABG (elevated lactate)
- CXR (hyperinflation, interstitial fluid)
- Allergy testing follow up
Describe management of anaphylaxis
- CPR and ALS if arrested
- ABCDE
- IM adrenaline 0.5ml 1:1000
- Airway + high flow oxygen, legs in the air
- IV fluids, chlorphenamine and hydrocortisone
- Cardioresp assess
- Consider nebulised adrenaline, SABA, atropine, glucagon
After initial treatment
- Antihistamine (chlorphenamine)
- Corticosteroid (hydrocortisone sodium succinate)
- Monitor for biphasic reaction
- Review by senior clinician and observation
- Give patient adrenaline auto-injector (eg. Epipen)
List complications of anaphylaxis
- MI
- Recurrence
Describe prognosis of anaphylaxis
- Severity of previous reaction does not predict severity of subsequent events, treatment does
- Serious sequelae of inadequate brain perfusion may occur, prognosis of MI depends on comorbidities and patient age
Which skin condition is aspirin linked to?
Urticaria
What specific inflammatory marker is raised in sepsis?
TNFa
Compare sepsis, septic shock and SIRS
- SIRS consists of changes in clinical signs including an abnormal body temperature, increased heart rate, increased respiratory rate, an abnormal white cell count (either decreased or elevated), or an increase in band neutrophils due to a severe inflammatory response resulting in organ dysfunction
- Sepsis is SIRS with an infectious cause. Life threatening organ dysfunction caused by dysregulated host response to infection
- Septic shock is lactate over 2mmol/l despite good fluid resucitation, or patient requiring vasopressers to maintain MAP over 65
- Septicaemia is an infection in the bloodstream
Define SLE
A chronic multi-system disorder that most commonly affects women during their reproductive years. It is characterised by the presence of antinuclear antibodies
Describe epidemiology of SLE
- Age 15-45 most commonly
- 9 times more common in females
- Over age 45, 2 times more common in females
- 97 per 100000 prevalence UK
- More common and more severe in those of African descent
Describe aetiology of SLE
- Genetic factors (familial aggregation, higher concordance in twin studies, more common if compliment deficiency). 95% ANA +ve, anti-dsDNA more specific. Associated with HLA B8, DR2 and DR3
- IRF5 gene polymorphisms
- Environmental factors (non-infectious like drugs, and infectious like epstein barr, smoking)
List symptoms and signs of SLE
- Malar (butterfly rash)
- Photosensitivie rash
- Discoid rash
- Fatigue
- Weight loss
- Fever
- Oral ulcers
- Alopecia
- Arthralgia/arthritis
- Fibromyalgia
- Raynauds
- Chest pain SOB
- Venous or arterial thrombosis
- Hypertension
- Signs of nephrosis
- Lymphadenopathy
- Abdo pain, vomiting, diarrhoea
- Nose ulcers, poorly localised proximal limb inflammatory pain with weakness
- Dysrhythmias, conduction defects, or unexplained cardiomegaly
- CNS signs (psychosis, seizures)
- Dysphagia
List risk factors for SLE
- Female sex
- Age 15 to 45 years
- African/Asian descent
- Drugs (procainamide, minocycline, phenytoin, carbamasepine)
- Sun exposure
- Family history (DR3 and 4)
- Tobacco smoking
Describe investigations of SLE
- FBC (anaemia, leukopenia, thrombocytopenia)
- aPTT (may be prolonged)
- U and E (urea and creatinine raised)
- ESR and CRP (raised, CRP normally lower or even normal)
- ANA, dsDNA, smith antigen (positive, smith and dsDNA very specific for SLE)
- Urinalysis (haematuria, casts, proteinuria)
- CXR (pleural effusion, infiltrates, cardiomegaly)
- ECG
Define vasculitide
- Heterogeneous group of autoimmune disease characterised by inflammation of blood vessels (vasculitis) and subsequent ischaemia and damage to the organs supplied by these vessels
- Primary is idiopathic
- Secondary has an underlying cause
- May be small vessel, medium vessel or large vessel
Describe aetiology of vasculitides
- Primary is idiopathic
- Secondary may include response to hep B, hep C, myeloma or autoimmune disease
Define eosinophilic granulomatosis with polyangiitis
A multisystem disease characterised by necrotizing granulomatous vasculitis with eosinophilia. Most commonly affects the lungs and skin but can affect the renal, CV, GI, central and peripheral nervous system. Also called Churg Strauss syndrome
Describe epidemiology of eosinophilic granulomatosis with polyangiitis
- 1-3 cases per million people.
- 67 per million in asthma patients
- Typically diagnosed in middle age
- Male predominance
List risk factors for eosinophilic granulomatosis with polyangiitis
- Asthma, allergic rhinitis or sinusitis
- Use of some medications (macrolide antibiotics and quinidine)
List symptoms of eosinophilic granulomatosis with polyangitis
- Focal numbness or weakness
- Nasal discharge or stuffiness or facial pain
- Haemoptysis
- Fatigue, arthralgias, myalgias
- SOB/cough
- Abdo pain
- Orthopnoea
List signs of eosinophilic granulomatosis with polyangiitis
- Palpable purpura and petechiae
- Wheeze
- Skin nodules
- Sensory or motor deficit
- Tachypnoea
- Rales
- Peripheral oedema
- Hepatojugular reflux
List investigations for eosinophilic granulomatosis with polyangiitis
- FBC (raised eosinophils)
- Serum anti-neutrophil cytoplasmic antibodies (+ve pANCA)
- CRP (raised)
- ESR (raised)
- U and E, urinalysis (glomerulonephritis)
- Pulmonary function test (reversible airway obstruction
- CXR
- ECG (left ventriular wall abnormalities, intracardiac thrombus, pericardial effusion)
- Flow cytometry of peripheral blood (normal)
- Mutation testing
- IgE (raised)
- Stool sample
- CT chest (may show pulmonary nodules)
- Electromyogram
- BAL/broncoscopy
- Biopsy affected tissue
Define granulomatosis with polyangiitis
A systemic vasculitis that typically involves small and medium vessels. Although any organ may be targeted, the classic triad consists of upper and lower respiratory tract involvement and pauci-immune glomerulonephritis. Also called Wegners Granulomatosis.
C disease- curvy nose, cANCA, chronic sinusitis
Describe epidemiology of granulomatosis with polyangiitis
- In the US 3 per 100,000
- In Sweden 160 per million
- Can occur at any age (mean age 40-60)
- Equal gender distribution
- Most common in white people
List risk factors/aetiology for granulomatosis with polyangiitis
- Genetic predisposition
- Infection
- Environmental factors (silica, heavy metals, other chemicals)
List signs and symptoms of granulmatosis with polyangiitis
- Upper respiratory tract (otorrhoea, pain in ears, sinus pain, nasal discharge, epistaxis, hoarseness, stridor, ulcers, mucosal bleeding, sinus tenderness)
- Saddle nose
- Lowe respiratory tract (SOB, cough, heamoptysis, chest pain, dyspnoea, dullness on percussion, crackles)
- Renal involvement (oedema, hypertension)
Non-triad:
- Non specific symptoms eg. fatigue, malaise, weight loss, night sweats, anorexia
- Ocular manifestations (eg. redness, visual loss and pain)
- Cutaneous manifestations (purpura or petichea, ulcerative lesions)
- Musculoskeletal manifestations (myalgia/artralgia)
- Neurological manifestations (mononeuritis multiplex)
- Thromboembolism
- GI involvement (abdo pain, vomiting, diarrhoea, blood or mucus in stool)
- Cardiac involvement (pericarditis, myocarditis - chest pain, fatigue cough wheeze oedema)
- Breast mass
- Lower GU tract (dysuria/pelvic pain)
- Endocrine involvement
List investigations for granulomatosis with polyangiitis
- Urinalysis and microscopy (haematuria, proteinurea, RBC casts, dysmorphic red blood cells)
- CT chest/CXR (lung cavitations)
- Anti-neutrophil cytoplasmic antibody (ANCA - positive sufficient for diagnosis with otorhinolarygeal, lung and renal involvement. cANCA 80% or pANCA 15%)
- FBC (anaemia)
- Serum creatinine (raised)
- Erythrocyte sedimentation rate (ESR- raised)
- Tissue biopsy (granulomatous inflammation, necrosis and vasculitis, minimal immune deposits)
- Pulmonary function testing
- Bronchoscopy
- Electromyography/nerve conduction studies
- Upper airway endoscopy
- CT sinuses
Define microscopic polyangiitis
Necrotising vasculitis of small vessels typically with renal, pulmonary and skin involvement. Nasopharynx not affected
List common signs and symptoms of microscopic polyangiitis
- Renal (90%) pauci-immune glomerulonephritis with hypertension
- Lungs (50%) pulmonary vasculitis with haemoptysis - no URT
- Skin (40%) palpable purpura, nodules, necrosis
- Tiredness, anorexia, joint and muscle aches
- Mononeuritis multiplex
Describe investigations for microscopic polyangiitis
- Biopsy of involved organ (fibrinoid necrosis with infiltration of neutrophils, no granulomas)
- MPO-ANCA/pANCA, U and E, Creatinine
- Urinalysis for haematuria and proteinuria
- CXR showing cavitating lesions
Describe epidemiology of microscopic polyangiitis
- Commonest in middle aged people
- Affects both men and women
Define polyarteritis nodosa
Necrotising inflammation of medium-sized or small arteries without glomerulonephritis or vasculitis in arterioles, capillaries, or venules
Describe epidemiology of polyarteritis nodosa
- Progressively becoming less common
- 2 - 9 per million/year in Europe and US
- 31 - 33 per million in western europe
- Higher where HBV is endemic
- 40-60 most common
Describe aetiology of polyarteritis nodosa
- Hepatitis B implicated very commonly
- Deposition of immune complexes
- Genetic, infectious and environmental agents may be important
List risk factors for polyarteritis nodosa
- Hepatitis B virus (HBV) infection
- Age 40 to 60 years
- Hairy cell leukaemia
- Blood transfusion at a time before routine screening for HBV
- Hepatitis C virus (HCV) infection
- Male sex
List symptoms of polyarteritis nodosa
- Fever
- Weight loss
- Myalgia or arthralgia
- Paraesthesia
- Muscle tenderness
- Abdominal pain
- Testicular pain
- Seizure
- GI bleeding
- Peritonitis (ischaemic bowel- pain)
- Monocular blindness
- Chest pain (ischaemic)
- Congestive cardiac failure
- Tender breast lumps
- Skin: livedo retiularis
List signs of polyarteritis nodosa
- Skin manifestations (peripheral neuropathy)
- Diastolic blood pressure >90 mmHg
- Mononeuritis multiplex
- Upper motor neuron weakness
- Peritonitis (tender rigid abdomen, patient immobile)
List investigations for polyarteritis nodosa
- CRP (raised), ESR (raised), FBC (normocytic anaemia, rasied WBC and platelets), LFT, complement (reduced), creatinine
- Midstream urine analysis
- HBV + HCV serology
- Cryoglobulins (no- HCV)
- Blood culture
- Creatine kinase
- ANCA, ANA, anti-dsDNA, rheumatoid factor, anti-CCP antibodies, lupus anticoagulant, IgG antiphospholipid antibodies (negative)
- B2 glycoprotein
- Fibrinogen
- Conventional digital subtraction angiography (microaneurysms, vessel ectasia, or focal occlusive lesions in medium-sized vessels)
- Echocardiography
- Magnetic resonance angiography (MRA) rosary sign
- CT angiography ROSARY SIGN (bead like appearance on angiogram)
- Biopsy of affected tissue
- HIV serology
Define takayasu arteritis
- A chronic granulomatous vasculitis affecting large arteries: primarily the aorta and its main branches.
- Vascular inflammation can cause stenosis, occlusion, and aneurysm formation.
Describe epidemiology of takayasu arteritis
- US 2.6 cases per million
- In Japan 1 in every 3000 autopsies
- Women affected 8 times more in japan, but men and women affected equally in India
- The peak incidence is usually in the third decade of life, although among Japanese people it typically presents between the ages of 15 and 25. In European people the mean age at diagnosis is 41.
- Patients in the US are more likely than those in Japanto have constitutional and musculoskeletal symptoms, claudication, and visual changes
- More common in women
Describe aetiology of takayasu arteritis
- Environmental and genetic factors are thought to play roles in the development of the disease.
- Cell-mediated immune mechanisms have been implicated.
- Genetic screening has shown polymorphisms in IL-12, IL-6, and IL-2 genes
- HLA-Bw5 and HLA-B39.2 are reportedly increased in frequency in some populations.
List risk factors for takayasu arteritis
- Genetic predisposition
- Female sex
- Age <40
- Asian ethnicity