Acute Crystal + Septic Arthropathies Flashcards
A patient presents with a red hot swollen joint that appeared suddenly in the last few days, what are the 4 main conditions you should be worried about?
Septic Arthritis (SeA)
Crystal Arthropathies (Gout + Pseudo-gout)
Dactylitis
Osteomyelitis
What is septic arthritis?
A serious infection of the joints characterised by fever, chills, severe pain, inflammation & swelling in 1 (or more) joints, and loss of function in those joints
Considered an emergent condition, immediate IV antibiotics required
What can septic arthritis cause if untreated?
Rapid and severe damage to articular bone and cartilage (can be irreversible within 48 hours)
Potential systemic or fatal sepsis
How does SeA happen?
Infective micro-organisms reaching the synovial membrane of a joint, inciting the inflammatory response. This can happen through the following:
- Haematologenous route - Infection carried in the bloodstream from another site of infection
- Trauma introducing a portal for infection
- Intra-articular injection, aspiration or surgery creating a portal for infection
- Osteomyelitis/ infection of surrounding bone or infection adjacent soft tissues - Infection spreads to the joint capsule secondary to surrounding infection
How is SeA diagnosed?
The presence of clinical signs + symptoms (sudden onset fever, chills, pain, inflammation and swelling in one or more joints with loss of function)
Joint aspiration and culture sensitivity of synovial fluid - testing for gram +/- bacterial infections, rule out gout e.t.c
Full Blood Count - testing for elevated levels of leukocytes and raised ESR and CRP
X-Ray and US - can assess levels of joint damage and inflammation
What bacteria are commonly associated with SeA?
Staphylococcus Aureus - most common cause in adults
Streptococci - 2nd most common cause
Haemophilius Influenza - was most common but is now relatively uncommon in vaccinated areas
Neisseria Gonorrhea - most common cause in young adults
E.Coli - most common cause in the elderly, IV drug users and the seriously ill
M.Tuberculosis, Salmonella + Brucella - most common cause of spinal septic arthritis
Pseudomonas Aeruginosa - Common in children who have sustained a puncture wound
What features can be seen in diagnostic imaging of joints affected by SeA?
X-Ray: In early stages of SeA radiograph should appear normal, if infection is not immediately controlled you may see joint space narrowing and pitting/erosion of the subchondral bone
US: Joint swelling with anechoic joint effusion and increased vascularity/ overlying power Doppler signal
What joints can SeA affect?
Can affect any joint but common to large and weight bearing joints
Also common to ankle, 1st MTPJ, hip, knee and shoulder
What are some risk factors that increase the risk of developing SeA?
SeA can affect anyone but risk is increased in patients who…
Are of advancing age
Are immunocompromised (e.g in RA and diabetes)
Are immunosuppressed (on DMARDs, biologics, steroids)
Are post surgery (risk of infection)
Have had a recent injury
Have a current infection (e.g strep throat)
Have a prosthetic joint implanted (can cause secondary infection)
Are IV drug users
What are crystal arthropathies?
Inflammatory response to the deposition of crystals in the synovial lining of joints
Main 2 common types are…
Gout - Caused by monosodium urate/ Uric acid crystals
Pseudo-gout (Calcium Pyrophosphate Deposition Disease) - Caused by calcium pyrophosphate crystals
Define Gout
An inflammatory response to a deposition of monosodium urate crystals in and around joints. Linked to high purine diet.
Can be an isolated acute attack, or chronic and recurrent.
Compared to a healthy joint, in a joint affected by gout, because of the deposition of uric acid crystals in the synovium of the joint, there is a secondary inflammatory response, with localised redness, heat & swelling.
There can also be formation of tophi around the joint, which can sometimes be seen under the skin subcutaneously.
Can occur at any age but usually between 30-60 years old and middle age men are most commonly affected.
What are the typical sites for gout to occur?
Most common site is 1st MTPJ, but can also occur in ankles, knees, elbows, wrists and fingers
Most commonly presents in one joint but can also present as polyarthritis
What are the signs and symptoms of an acute attack of gout?
Sudden onset of dull aching pain in joint, that builds up over 2-3 hours into extreme pain, along with erythema, oedema and heat at the affected joint.
Cannot bear weight on affected joint
Usually presents at 1st MTPJ
Attack can begin suddenly in the night
Possible mild fever: leukocytosis and raised ESR
Elevated serum urate levels
Can last 2-4 days or weeks: subsides leaving a normal joint but is often followed by further attacks
What are the signs and symptoms of chronic tophaceous gout?
Repeated acute attacks of gout
Palpable visible nodules form over joint called ‘Tophi’ - occur due to the accumulation of urate crystals over articular cartilage
Rate of tophi formation correlates with duration and severity of hyperuricaemia
Tophi may ulcerate, or compress blood vessels and nerves
Patient will often suffer from some kind of renal impairment, recurrent attacks of gout due to inability to filter uric acid from blood
Describe the pathogenesis of gout?
Purines are broken down by the body into uric acid
Gout is a disorder where the metabolism of uric acid is hindered - causing hyperuricemia, which is caused by either under-excretion or over-production of uric acid in the body
Hyperuricemia causes uric acid to be deposited in the joints or tendons (in the surrounding synovial fluid)
The presence of uric acid in the joints initiates the inflammatory response (interleukin 1 has been linked specifically to this process)
Several events can encourage crystals to move and trigger an acute attack (such as excessive purine consumption, dehydration, illness and surgery)
What are some risk factors for the development of gout?
High Purine Diet - Red meat, seafood (mackerel), fresh fruit juice
Excessive Alcohol Consumption- Competes with uric acid for excretion and/or damages kidneys
Diuretics
Metabolic Syndrome - Obesity, diabetes, hypertension, high cholesterol
Coronary Heart Disease
Chronic Renal Failure
High Triglycerides
Genetic Predisposition
What is considered a normal range for plasma urate levels in the blood?
Between 200 to 410 umol/L or 3.3 to 6.9 mg/dL
What would the serum urate level of an individual affected by gout be?
Gout is considered when serum urate level is >6.9 mg/dL
But gout can occur at values as low as 6 mg/dL, and a person with serum urate levels as high as 9.6 mg/dL can be asymptomatic and not have gout
Name some ultrasound features of gout?
Double line sign (urate crystals lining hyaline cartilage)
Soft tissue swelling
Hyperechoic (reflective) dotted foci, tophi, erosions, and active inflammation.
Involvement around joints & tendons.
How is gout treated?
Conservative Management…
Advise on weight loss, low purine diet, alcohol reduction, avoidance of diuretic therapies, avoiding trauma to affected joint, increasing fluid intake
Ice, rest and elevation
Keep joint exposed and in cool environment
Pharmacological Management…
NSAIDS - for acute attack
Colchicine - to reduce inflammatory response to urate crystals by inhibiting leukocytes lactic acid production, interrupting urate deposition and inflammatory response
Corticosteroids - to suppress inflammation
Allopurinol or Febuxostat - urate lowering drugs for chronic gout
What is pseudo-gout?
A condition involving inflammation in joints due to the deposition of calcium pyrophosphate crystals
Can be acute and self limiting or chronic
Most commonly affects older women
How does pseudo-gout typically present?
As an acute mono or oligoarthritis, mostly affecting knees, wrists, shoulders, hips, hands and feet
Similar presentation to gout but usually milder, less pain and inflammation
When chronic, there can be destructive changes like in osteoarthritis but worse, which can cause complete joint failure & induce neuropathy in a joint.
What risk factors contribute to the development of pseudo-gout?
Dehydration
Thyroid disorders
Long term steroid use
Haemochromatosis
Wilson’s disease (linked to excess copper in the body)
Acromegaly
Dialysis
Surgery or trauma
Hypomagnesaemia
