How does Antiphospholipid antibodies syndrome (APS) cause bruising?

Antiphospholipid Syndrome and Bruising: Mechanisms and Management

Antiphospholipid syndrome (APS) causes bruising primarily through thrombocytopenia, which occurs in approximately 20-25% of patients with APS. 1 This thrombocytopenia creates a paradoxical situation where patients simultaneously face increased risks of both thrombosis and bleeding.

Pathophysiological Mechanisms of Bruising in APS

Primary Mechanisms:

1. Thrombocytopenia

   • Present in 20-25% of APS patients 1
   • Usually mild but can be severe in some cases 2
   • Multifactorial mechanism:
     • Immune-mediated platelet destruction
     • Decreased platelet production
     • Consumption during thrombotic events

2. Coagulation Abnormalities

   • Antiphospholipid antibodies interfere with normal coagulation processes
   • Three main antibody types involved 3:
     • Lupus anticoagulant (LA)
     • Anticardiolipin antibodies (aCL)
     • Anti-β2 glycoprotein I antibodies (aβ2GPI)

3. Vascular Manifestations

   • Microvascular injury from thrombotic events
   • Livedo reticularis (netlike pattern of discolored skin) 3
   • Skin necrosis in severe cases 1

Clinical Presentation and Diagnosis

Key Clinical Features:

• Bruising (petechiae, purpura, ecchymoses)
• Concurrent thrombotic events (paradoxical)
• Pregnancy morbidity in women
• Livedo reticularis
• Other manifestations: skin necrosis, neuropsychiatric events 1

Diagnostic Approach:

1. Laboratory Testing

   • First-line testing should include all three antibodies 3:
     • Lupus anticoagulant (LA)
     • Anticardiolipin antibodies (aCL)
     • Anti-β2 glycoprotein I antibodies (aβ2GPI)
   • Confirmation of persistent antibodies at least 12 weeks apart 3
   • Complete blood count to assess platelet levels
   • Coagulation studies (PT, aPTT)

2. Risk Stratification

   • Triple antibody positivity confers highest thrombotic risk 3
   • Double positivity: intermediate risk
   • Single positivity: lowest risk

Management of APS with Thrombocytopenia and Bruising

Treatment Algorithm:

1. Assess Severity of Thrombocytopenia

   • Mild (>50,000/μL): Monitor closely
   • Moderate (20,000-50,000/μL): Consider treatment if bleeding
   • Severe (<20,000/μL): Active intervention needed

2. Balancing Thrombotic and Bleeding Risks

   • Important caveat: Thrombocytopenia does not reduce thrombotic risk in APS patients 4
   • Patients may require both anti-thrombotic therapy and treatment for thrombocytopenia

3. Treatment Options:

   • For thrombocytopenia causing significant bleeding:

     • Corticosteroids (first-line)
     • Intravenous immunoglobulin (IVIg)
     • Rituximab in refractory cases

   • For thrombosis prevention (when platelets allow):

     • Vitamin K antagonists (warfarin) targeting INR 2.0-3.0 for venous thrombosis 3
     • Avoid direct oral anticoagulants (DOACs) in triple-positive APS patients due to increased thrombotic risk 3
     • Low-dose aspirin for arterial thrombosis prevention

Special Considerations

1. Pregnancy Management

   • Combination therapy with low-dose aspirin and prophylactic LMWH 3
   • Start aspirin preconceptionally and LMWH when pregnancy confirmed
   • Continue treatment until 6 weeks postpartum

2. Catastrophic APS

   • Aggressive intervention required with:
     • Anticoagulation (heparin initially)
     • High-dose glucocorticoids
     • Plasma exchange 3

3. Secondary APS

   • Treat underlying condition (e.g., SLE) concurrently
   • Monitor for exacerbations of both conditions

Common Pitfalls to Avoid

1. Misinterpreting prolonged aPTT as a contraindication to anticoagulation

   • A prolonged aPTT due to lupus anticoagulant is not a contraindication to anticoagulation therapy 5

2. Underestimating thrombotic risk in thrombocytopenic patients

   • Thrombocytopenia does not reduce thrombotic risk in APS 4

3. Using DOACs in high-risk APS patients

   • DOACs are not recommended for triple-positive APS patients 3

4. Discontinuing anticoagulation prematurely

   • Long-term (often indefinite) anticoagulation is typically required 5

By understanding the complex interplay between thrombosis and bleeding in APS, clinicians can better manage the paradoxical risks these patients face and improve outcomes.