Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by a combination of arterial or venous thrombosis and recurrent fetal loss, accompanied by elevated titers of antiphospholipid antibodies (aPL). Catastrophic antiphospholipid syndrome (CAPS) is a small subset of APS characterized by widespread systemic thrombotic disease with multiorgan failure. We herein describe an autopsy case of CAPS who developed severe respiratory failure due to acute respiratory distress syndrome (ARDS) as the initial manifestation. Patients with APS may exhibit a broad spectrum of pulmonary diseases. ARDS is the common pulmonary complication in CAPS, although it rarely occurs in APS. Some mechanisms of ARDS in CAPS have been postulated but the precise mechanism is still not clearly understood. It is important to understand that APS or CAPS could be a cause of ARDS since ARDS might develop as the initial manifestation of APS or CAPS as seen in our case. Our case is interesting in that severe respiratory failure due to ARDS was the initial presentation of CAPS.