Rheumatology Week 4 Summary

Question 16

What are the diagnostic criteria for rheumatoid arthritis?

  • Morning stiffness lasting >1 hour
  • Arthritis of 3 or more joints
  • Hand joint arthritis
  • Symmetrical joint involvement
  • Rheumatoid factor positivity
  • Periarticular erosions
  • Rheumatoid nodules

A patient is classified as having rheumatoid arthritis if 4 of these 7 criteria are present. The first 4 must be present for >6 weeks.

Assays for anti-CCP antibodies can also be helpful in the diagnosis of RA, though they have not been included to date in the classification criteria. Anti-CCP antibodies are more specific (~90%) for rheumatoid arthritis than RF and they have a similar sensitivity. Their presence also predicts erosive disease.

Question 17

What are the 5 major diagnostic features of polymyositis and dermatomyositis?

  • Proximal muscle weakness
  • Myopathic features on EMG testing
  • Elevated muscle enzymes (Primarily the CK, though elevations of AST and LDH are also seen).
  • Presence of a typical skin rash (in the case of dermatomyositis)
  • Positive muscle biopsy (note that the histological features of PM and DM are different. PM is characterized by endomyseal infiltration of inflammatory cells, most of which are CD4+ cells. In DM, an inflammatory infiltrate is seen in the perivascular and perifascicular regions).

Question 18

Name three drugs that cause hyperuricemia and may contribute to gouty arthritis. What antihypertensive drug lowers uric acid levels?

  • Cyclosporine
  • ASA
  • Nicotinic acid
  • Thiazide diuretics
  • Lasix
  • Ethambutol
  • Alcohol
  • Pyrazinamide

You can remember these using the mnemonic “CAN’T LEAP”.

The ARB losartan has a uric acid-lowering effect.

Question 19

Which 5 joints are most commonly affected in rheumatoid arthritis?

  • MCP joints
  • Wrist joints
  • PIP joints
  • Knees
  • MTP joints

Less frequently involved joints are the ankles, C-spine (particularly C1-C2), elbow, hip and TMJ.

Question 20

Name 4 reasons for a spuriously elevated ESR.

  • Pregnancy
  • End-stage renal disease
  • Anemia
  • Advanced age
  • Female sex

As a general rule, expected elevations in ESR due to advanced age or sex can be calculated according to the following equation:

ESR (mm/hr) >age (+ 10 for women) / 2

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