Updated: 11/26/2019

Pseudogout

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Snapshot
  • A 60-year-old man presents to the emergency department for severe left knee pain. His symptom began approximately 8 hours prior to presentation. He denies trauma to the joint and this is the first time this occurred. Medical history is significant for hemochromatosis managed with weekly phlebotomy. On physical exam, the left knee is erythematous, warm, enlarged, and tender to palpation. Radiography of the affected joint demonstrates chondrocalcinosis. Joint aspiration demonstrates a leukocyte count of 2500/mm3 with a negative Gram stain. Polarized microscopy shows weakly positively birefringent rhomboid crystals.
Introduction
  • Clinical definition
    • a metabolic arthropathy due to deposition of calcium pyrophosphate dihydrate (CPP) in connective tissue
  • Epidemiology
    • risk factors
      • radiographic CPP deposition increases with age
  • Etiology
    • CPP deposition in joints
  • Pathogenesis 
    • aging and/or genetic factors may result in increased adenosine triphosphate breakdown producing inorganic pyrophosphate 
      • CPP is produced after inorganic pyrophosphate binds with calcium
        • CPP then deposits in cartilage and synovial fluid leading to a synovitis
  • Associated conditions
    • hemochromatosis  
    • hyperparathyroidism
    • hypomagnesemia
      • can be seen in Gitelman and Bartter syndrome
    • joint trauma, surgery, and severe medical illness
      • these conditions can provoke an acute attack
  • Prognosis
    • acute attacks typically resolve in 10 days
    • patients may experience functional limitation due to joint damage
    • may resemble osteoarthritis or rheumatoid arthritis
Presentation
  • Symptoms
    • asymptomatic (most cases)
    • acute attack (pseudogout)
      • typically affects the wrists, knees, and metacarpophalangeal joints
      • clinically indistinguishable from gout
      • symptoms and physical exam findings include
        • pain
        • erythema
        • warmth
        • swelling
        • disability of the affected joint
    • "pseudo-rheumatoid arthritis"
      • inflammatory arthritis symptoms
        • joint pain and morning stiffness
    • pyrophosphate arthropathy
      • resembles osteoarthritis 
Imaging
  • Radiography
    • indication
      • to assess the affected joint
    • findings
      • chondrocalcinosis and degenerative changes 
        • chondrocalcinosis appears as hyperdensities that are punctate and linear  
Studies
  • Arthrocentesis
    • confirms the diagnosis
    • Gram stain and culture should always be performed since infection could co-exist
    • leukocyte count is 2,000-100,000/mm3
      • > 50% polymorphonuclear cells 
    • polarized microscopy demonstrates weakly positively birefringent rhomboid crystals  
      • blue when parallel to light and yellow when perpendicular to light
Differential
  • Gout 
    • differentiating factor
      • polarized microscopy demonstrates negatively birefringent crystals 
      • more commonly affects the first metatarsophalangeal (MTP) joint 
Treatment
  • Conservative
    • observation
      • indication
        • in patients with asymptomatic chondrocalcinosis
  • Medical
    • nonsteroidal anti-inflammatory drugs (NSAIDs)
      • indication
        • an initial treatment option for pseudogout
    • colchicine
      • indication
        • an initial treatment option for pseudogout
    • glucocorticoids
      • indications
        • injections of the affected joint is typically used in patients with < 2 involved joints
        • oral medications are typically used in patients with > 2 involved joints
Complications
  • Joint damage

 

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(M2.RH.15.73) A 64-year-old male presents to his primary care physician with a chief complaint of left knee pain. He describes acute-onset knee pain last evening that was accompanied by redness of the skin around the joint. He denies any precipitating injury or recent activity that could have caused this pain. He describes a similar episode that occurred in his right knee 2 months ago; he did not seek medical treatment, and the pain mitigated after 5 days. Physical examination is significant for the following: left knee is warm-to-touch, erythematous, and extremely tender to palpation; range of motion in flexion and extension is limited by pain; crepitus noted with passive movement of the knee joint. The patient is noted to be afebrile with all vital signs within normal limits. Aspiration of the left knee joint is ordered and reveals the findings shown in Figure A. Which of the following findings could also be seen in this patient, associated with their current diagnosis? Tested Concept

QID: 106581
FIGURES:
1

Decreased serum calcium levels and elevated phosphate levels

38%

(11/29)

2

Autoimmune destruction of pancreatic islet cells and elevated blood glucose levels

3%

(1/29)

3

Insulin insensitivity and elevated blood glucose levels

0%

(0/29)

4

Bronzing of the skin and elevated blood glucose levels

52%

(15/29)

5

Kayser-Fleischer rings and decreased serum ceruloplasmin

0%

(0/29)

M 6 D

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