Catastrophic Antiphospholipid Syndrome Characteristics
Catastrophic APS is characterized by thrombosis affecting multiple organs with rapid onset and high mortality (options a, b, c are correct), while low mortality (d) and always coexisting with SLE (e) are incorrect. 1
Correct Characteristics
a) Features of Microangiopathy - TRUE
CAPS is fundamentally a thrombotic microangiopathy. The histopathological hallmark is acute thrombotic microangiopathy with multiple small-vessel occlusions 2, 3. The 2024 KDIGO guidelines explicitly describe CAPS as characterized by thrombosis affecting multiple organs, often with features of microangiopathy 1. This distinguishes it from large-vessel thrombosis seen in typical APS.
b) Triggering Mechanism Associated with Infection - TRUE
A precipitating factor can be identified in the majority of CAPS patients. The most common triggers include 2:
- Infections (most frequent)
- Surgery
- Medications
- Trauma
This triggering mechanism is clinically important because identifying and treating the precipitant is part of optimal management.
c) Occurrence of Thrombosis in Multiple (>3) Organs - TRUE
Multi-organ involvement is definitional for CAPS. According to the preliminary classification criteria validated in 2005, CAPS requires evidence of involvement of three or more organs, systems, and/or tissues 3. The most commonly affected organs include 4, 3:
- Kidneys (70%)
- Lungs (66%)
- Central nervous system (60%)
- Heart (52%)
- Skin (47%)
The combination of pulmonary, cardiac, and renal involvement is most frequently observed 4.
Incorrect Characteristics
d) Low Mortality - FALSE
CAPS carries a mortality rate of approximately 48%, making it a life-threatening emergency 3. This high mortality rate has been consistently reported across multiple studies 2, 5, 6, 7. Recent case reports from 2025-2026 continue to demonstrate fatal outcomes despite aggressive treatment 8, 6, 7, emphasizing that CAPS remains one of the most severe autoimmune emergencies.
The best survival rates (63%) are achieved with combination therapy including anticoagulation plus steroids plus plasma exchange or intravenous immunoglobulins 3.
e) Always Coexisting with SLE - FALSE
CAPS does NOT always coexist with SLE. While antiphospholipid antibodies are found in approximately 30% of patients with SLE 1, and APS can be secondary to SLE 9, nearly half of patients who develop CAPS do not have a history of prior APS or antiphospholipid antibody positivity 10. CAPS can occur as:
- Primary CAPS (not associated with other autoimmune disease)
- Secondary CAPS (associated with SLE or other rheumatological disorders)
Recent case reports document de novo CAPS in previously healthy individuals without any prior autoimmune disease 8, 7.
Clinical Pearls
Key diagnostic features to recognize CAPS:
- Rapid onset (developing over days to weeks, not months)
- Evidence of involvement of ≥3 organs
- Laboratory confirmation of antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, or anti-β2-glycoprotein I antibodies)
- Histopathological evidence of small-vessel occlusion
- Systemic inflammatory response syndrome often accompanies CAPS 2
Common pitfall: Despite widespread intravascular coagulation, blood films reveal only a small number of schistocytes, and severe thrombocytopenia is uncommon 2. This can lead to delayed diagnosis if clinicians expect findings typical of other thrombotic microangiopathies like TTP.