JC84 (Medicine) - SLE Flashcards
SLE
Definition
Chronic multisystem autoimmune disorder
Characterized by immunological disturbances resulting in excessive production of autoantibodies
Causing direct tissue damage and immune complex-mediated tissue or organ inflammation
SLE
Typical demographics
Genetic risk factors
Female: Male = 9:1
Most common in blacks, 50-70/100k in Orientals
Genetic predisposition
→ HLA-B8, DR2, DR3 or other genes that influence sex hormone status
→ complement deficiency (impaired phagocytosis)
High concordance rate in monozygotic twins
Increased risk of SLE in 1st degree relatives
Triggering events of SLE
→ Infections: EBV, parvovirus B19, rhabdovirus, HIV-1, adenovirus, salmonella
→ Drugs: Proxainamide, Hydralazine
→ Chemical agents: hydrazine, tartrazine, dyes, eosin, heavy metals (mercury, gold, cadmium)
→ Food: L-canavanine, e.g. alfalfa seeds and sprouts
→ UV light
List drugs that induce SLE and exacerbate SLE
Trigger:
Procainamide
Hydralazine
Others (rare): B-blocker, quinidine, penicillamine, isoniazid, phenytoin, chlorpromazine
Exacerbate:
Lovastatin
Sulphonamide
Estrogens
Pathogenesis of SLE
What is the role of B and T cells?
loss of self-tolerance in immune system secondary to predisposing genetic factors and environmental triggers
B-cell:
→ AutoAb production due to
- Reaction to self-antigens (eg. dsDNA, RNPs)
- Activation by helper T cells
→ Auto-antibodies form immune complex (consists of nuclear antigens, IgG and antinuclear antibodies)
→ deposit in tissues and organ, esp kidney, and activate complement system to cause inflammation and tissue damage
T lymphocyte changes:
→ ↓cytotoxic and suppressor T cells
→ ↑helper T cell pop’n → ↑production of autoAb
Defective phagocytosis
→ Defective phagocytosis of immune complexes or apoptotic cells
Name 2 classification criteria for SLE
Why are classifications useful?
SLICC: Consists of clinical features and immunological features
EULAR/ ACR guideline: Consists of clinical features and immunologic features
Use of classification:
- Distinguish SLE from spectrum of autoimmune rheumatic diseases
- No overlaping score/ double count of clinical or immunological features
- Clearly defined cut-off for SLE
Precipitating factors for SLE relapse *
Precipitating factors for relapse:
Drug non-compliance (most common)
Infection
Stress
• Physical stress including surgery
• Psychological stress
Pregnancy
Drug-induced
UV light exposure
Constitutional symptoms of SLE *
→ Fever: only during flares, readily remits with NSAIDs, paracetamol or steroids (no remission = think infection)
→ Weight loss: usually only during flares
→ Poor appetite, malaise: continuous even when no flares
Musculoskeletal features of SLE *
- *Arthritis**: early onset, symmetrical, migratory non-erosive polyarthritis
- Morning stiffness: in minutes (cf >1h in RA)
- Joint involvement: similar to RA, i.e. knees, carpal joints, PIPJ, NO DEFORMITIES
- Deforming variant (Jaccoud arthritis)
Avascular necrosis of femoral head
Osteoporosis
Myopathy: myalgia, tenderness and weakness
Myasthenia gravis
Cutaneous features of SLE *
Photosensitivity
Cutaneous lupus erythematosus: 3 forms
- Malar/ Butterfly rash (spares nasolabial folds)
- Subacute (annular / psoriaform): non-scarring, sparing of face
- Discoid lupus erythematosus: hyperkeratosis, follicular plugging lesions, scarring alopecia if on scalp
Cutaneous vasculitis
- Telangiectasia
- Raynaud phenomenon
- Periungual erythema
- Livedo reticularis
Oral ulcers: multiple, affect different sites
Erythema nodosum
Purpuric skin rash
Pulmonary features of SLE *
→ Chest infection
→ Pleuritis: always bilateral
→ Interstitial lung disease (3-9%): usually non-specific interstitial pneumonia (NSIP)
→ Pulmonary embolism and infarct
→ Rare: recurrent atelectasis, acute pneumonitis, pHTN, pulmonary haemorrhage
Cardiac features of SLE *
Pericarditis ± effusion: pleuritic substernal chest pain, audible rub
Coronary artery disease
Valvular disease, e.g. Libman-Sacks endocarditis (non-bacterial endocarditis, vegetation of fibrin and immune cells)
Myocarditis, Cardiomyopathy
Vascular features of SLE *
Raynaud phenomenon: intermittent acral pallor followed by cyanosis and erythroderma
Vasculitis (11-36%): most commonly small vessels but can also involve medium/large vessels
Thromboembolic disease: both arterial and venous circulations
Gastrointestinal features of SLE *
→ Esophagus: motility disorder (40%), infective esophagitis (e.g. Candida, CMV, HSV), pill-related oesophagitis
→ Liver: asymptomatic dLFT, AI hepatitis
→ Pancreas: acute pancreatitis
→ Intestine (rare): pseudo-obstruction, protein losing enteropathy, mesenteric vasculitis
Ocular features of SLE *
→ Keratoconjunctivitis sicca due to 2o Sjogren
→ Scleritis: deep boring eye pain, acute redness and photophobia
→ Acute visual loss
→ Chronic changes: corneal deposit, maculopathy, retinal vasculopathy (cytoid bodies)
Renal features of SLE *
→ Lupus nephritis**: isolated proteinuria/haematuria, nephrotic or nephritic syndrome due to Glomerulonephritis
→ Tubulointerstitial nephritis: presenting with tubular dysfunction, eg. ↓concentration ability
→ Renal vascular disease due to immune complex deposits or microvascular thrombosis