A 32 year old woman has malaise, fatigue, weight loss and fever


#1

A 32 year old woman has malaise, fatigue, weight loss and fever. On examination, a
Malar rash with sparing of nasolabial fold can be seen. She also complains of joint
stiffness and pain. What is the SINGLE most appropriate investigation?
A. Anti-dsDNA
B. Anti-histone
C. Anti-centromere
D. Anti-Jo-1
E. Anti-Scl-70
The signs and symptoms here point towards systemic lupus erythematosus (SLE). The 3
best initial test to order are anti-dsDNA titre, complement (C3 and C4) and ESR.
Systemic lupus erythematosus (SLE)
Important must know features for the PLAB exam

  • Remitting and relapsing illness
  • Mouth ulcers → large, multiple and painful
  • Lymphadenopathy
  • Malar (butterfly) rash: spares nasolabial folds
  • Discoid rash: scaly, erythematous, well demarcated rash in sun-exposed areas
  • Photosensitivity
  • Arthralgia
  • Raynaud’s phenomenon occurs in about one fifth of patients but is often mild
    Cardiovascular: pericarditis
  • Respiratory: pleurisy, fibrosing alveolitis
  • Renal: Glomerulonephritis (nephritis is often asymptomatic and is detected by
    proteinuria, haematuria, hypertension or a raised serum urea or creatinine)
  • Neuropsychiatric: anxiety and depression are common
    Investigation
    FBC and ESR:
  • Mild normochromic normocytic anaemia is common
  • ESR is raised
    Autoantibodies:
  • Antinuclear antibody (ANA)
    o Screening test with a sensitivity of 95% but not diagnostic in the
    absence of clinical features. It is a nonspecific antibody that is also
    present in many patients with systemic autoimmune conditions
  • Anti-dsDNA
    o Highly specific (> 99%), but less sensitive (70%)
  • Anti-Smith
    o Most specific (> 99%), but even less sensitive (30%-40%)
  • Anti-histone: drug-induced lupus ANA antibodies are often this type
  • 20% are rheumatoid factor positive
    Complement levels (C3, C4) are low during active disease (formation of complexes leads
    to consumption of complement)