SLE Flashcards
What is SLE
Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune condition caused by a type 3 hypersensitivity reaction due to a complex interplay between genetic and environmental factors.
Epidemiology
- Most commonly affects women in their reproductive years
- North America has the highest estimated incidence and prevalence of SLE
- Most common in African-Caribbean and Asians
- Peak age of onset is between 15 and 45 years old
Aetiology
- Genetics
- Environmental triggers e.g.
- UV light
- Smoking
- Medications e.g. procainamide, hydralazine, isoniazid
- Sex hormones e.g. oestrogen
- EBV
RF
- Middle-aged: peak age of onset is between 15 and 45 years old
- Female gender: SLE is 12 times more common in females
- African and Afro-Caribbean: SLE is more common and more severe in these patients; incidence amongst black Americans ishigherthan black Africans for unknown reasons
- Family history
- Drugs: procainamide, isoniazid, hydralazine may cause drug-induced Lupus
- HLA associations: HLA-B8, -DR2, -DR3
Pathophysiology
Environemental triggers (e.g UV light) cause cell death and apoptotic bodies - due to genes reduced clearance of apoptotic bodies and cellular debris
Immune system of patients dont recognise cellular debris as self so attack cell material forming nuclear antigen-antibody complex
These complexes deposit in diff tissues and activate complement causing inflammation and damage - type III hypersensitivy reaction
Where can the deposition occur
deposition can occur anywere so multiple organs are affected e.g. skin, joints, kidneys, heart and brain.
What do many patients also develop?
- develop antibodies targeting other cells:
- red and white blood cells
- various phospholipids- mark them for phagocytosis and destruction, leading to additional symptoms.
- This is considered a type II hypersensitivity reaction.
Classic presentation
Malar ‘butterfly’ rash (across cheeks but not nose), fatigue and widespread musculoskeletal pain in a middle-aged, African female.
The disease follows a relapsing and remitting course.
General symptoms
- Fatigue
- Fever
- Lymphadenopathy
- Weight loss
Many clinical manifestations
Photosensitivity
Arthralgia
PE
Pericarditis
Neonatal heart block
Lupus
Psychosis
Seizures
Thrombocytopenia
1st line investigations
FBC
U&E
ESR
CRP
Complement (C3 and C4)
Antibodies:
ANA
Anti-dsDNA
Rheumatoid factor
Anti-histone
Other investigations to consider
- Urinalysis: lupus nephritis may cause proteinuria and haematuria
- Skin or renal biopsy
- Imaging:consider joint X-rays in the presence of arthralgia or a chest X-ray if respiratory symptoms are present
Clinical criteria
- Malar rash
- Discoid rash
- Non-scarring alopecia
- Oral and nasal ulcers
- Synovitis
- Serositis
- Urinalysis (presence of proteinuria or haematuria)
- Neurological features
- Haemolytic anaemia
- Leucopenia
- Thrombocytopenia
Lab criteria
- +ve ANA
- Anti-dsDNA
- Anti-smith antibodies
- Antiphospholipid antibodies
- Low complement
- +ve direct Coombs test - detects antibodies that are stuck to the surface of RBCs
DD
- Scleroderma
- Rheumatoid arthritis
- Antiphospholipid syndrome
- Mixed connective tissue diseases (CTDs)
- Raynaud’s syndrome
- Sjögren’s syndrome