Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem disorder of autoimmune aetiology, affecting approximately 1 in 1000 people in the UK.

 

Pathophysiology

  • Type 3 hypersensitivity condition
    • A multi-system disorder caused by the formation of Immune complexes (Antigen:Antibody complexes) which are deposited in tissues around the body. 
  • Genetics: HLA-DR3, DR2 and B8 associated with increased risk of SLE

 

Epidemiology

  • Females (F9:1M)
  • African-Caribbean patients most commonly affected
  • Age of onset: 20-40 years

 

Clinical features 

  • General: Fever, fatigue, lymphadenopathy
  • Dermatological:
    • Photosensitive rash - especially in butterfly/malar distribution (sparing the nasolabial folds)
    • Livedo reticularis
  • Arthralgia
  • Cardiovascular - Pericarditis 
  • Respiratory - Fibrosing alveolitis 
  • Renal - Lupus nephritis - Diffuse proliferative glomerulonephritis  (wire-loop appearance) 

 

Complications of Pregnancy 

  • Maternal antibodies can cross the placenta and cause neonatal lupus erythematosus which can result in congenital heart block 

 

Investigations

Antibodies:

  • ANA – 95% sensitivity
  • Anti-dsDNA – 95% specific 
  • Anti-smith – 98% specific 

Monitoring disease activity:

  • In active disease CRP can be normal - so a high CRP might suggest infection
  • ESR and anti-dsDNA levels can be used for monitoring disease activity 
    • Low C3 and C4 levels may also reflect active disease due to consumption

 

Drug Induced Lupus 

Certain medications can result in a lupus-like disease referred to as drug induced lupus. The medications associated with the highest risk of DIL include:

  • Procainamide
  • Hydralazine
  • Isoniazid
  • Minocycline
  • Phenytoin

 

Clinical Features

  • Malar Rash
  • Pleurisy
  • Arthralgia, myalgia

  

Investigations

  • Patients are ANA positive,  but dsDNA negative (unlike SLE)
  • 90% of patients are anti-histone positive

  

Management

  • Stop the causative medication. 

 

 

Discoid lupus erythematosus

 

Clinical Features

  • Anular, erythematous, scaly lesions
  • Typically affect the face, scalp or ears
  • Lesions are characterised by follicular keratin plugs which can be identified by removing the superficial scale. 
    • Follicle sized keratotic plugs have a ‘carpet tack’ appearance (carpet tack sign)
  • The rash can be photosensitive. 
  • DLE results in scarring alopecia

 

Management

  • 1st line: topical steroids
  • 2nd line: hydroxychloroquine
  • Avoid sun exposure