Systemic Lupus Erythematosus (SLE)

• SLE fact sheet

Epidemiology

• More prevalent in Black, Caribbean, Asian, and Hispanic populations in the US.

Pathophysiology

• Primarily type III hypersensitivity reaction and to a lesser degree type II hypersensitivity reaction.
• Associated with deficiency of early complement proteins (e.g., C1q, C4, C3, C2) → ↓ clearance of immune complexes.

Classic Presentation

• Systemic, remitting, and relapsing autoimmune disease.
• Facial rash (sparing nasolabial folds)→ Malar rash , discoid rash.
• **joint pain (arthritis)**→ nonerosive
• Fever in a female of reproductive age.

Complications

• Lupus nephritis
  • Glomerular deposition of DNA-anti-DNA immune complexes
  • Can be nephritic or nephrotic (causing proteinuria or hematuria)
  • Most common and severe type is diffuse proliferative
• Libman-Sacks Endocarditis (LSE)
• Serositis (e.g., pleuritis, pericarditis)
• Hematologic disorders (cytopenias)
• Oral/nasopharyngeal ulcers (usually painless)
• Seizures , psychosis
• Death , caused by
  • Renal disease (most common)
  • Infections
  • Cardiovascular disease (accelerated CAD).
• Neonatal lupus

Diagnosis

• Autoantibodies
  • Anti-dsDNA
  • Anti-Sm
  • Antiphospholipid

<aside> ⏰

Remember

• Smith protein normally complexes with small nuclear RNA (SnRNA) to form (SnRNPs) which is important in RNA splicing. </aside>

<aside> 💡

Neonatal lupus

• Risk factors
  • Pregnant patient with positive anti-SSA
• Manifestations
  • Congenital heart block
  • Periorbital/diffuse rash
  • Transaminitis
  • Cytopenias

</aside>

                                **Malar rash**

                 **Malar rash**

          **Discoid rash**

     **Discoid rash**

Antiphospholipid Syndrome

Cause

• Primary or Secondary autoimmune disorder, often associated with SLE.

Diagnostic Criteria

• History of thrombosis (arterial or venous) or recurrent abortion
• Laboratory findings of
  • Lupus anticoagulant
  • Anticardiolipin antibodies
  • Anti-β2 glycoprotein I antibodies.

Treatment

• Systemic anticoagulation.

<aside> 💡 HY notes

• Anticardiolipin Antibodies→ Can cause false positive VDRL/RPR tests.
• Lupus Anticoagulant→ Causes prolonged PTT that is not corrected by normal platelet-free plasma. </aside>

Drug induced lupus erythematosus (DILE)

Clinical features

• Abrupt-onset symptoms
  • Fever/fatigue
  • Arthralgias/arthritis
  • Rash
  • Serositis
• Predilection for slow acetylators

Laboratory findings

• Antihistone antibodies present in >95% of patients
• Anti-dsDNA antibodies rarely seen (specific for SLE)

Implicated drugs

• Procainamide
• Hydralazine
• Isoniazid
• Minocycline
• TNF-a inhibitors (eg, etanercept)