RESUMEN
OBJECTIVES: To describe the pulmonary involvement in patients with catastrophic antiphospholipid syndrome (CAPS), focusing on its relationship with extrapulmonary involvement, laboratory, radiological, and pathological findings. METHODS: This retrospective cross-sectional study includes all patients grouped in the "CAPS Registry". All cases were reviewed, and those with pulmonary thromboembolism (PE) and/or diffuse alveolar hemorrhage (DAH) were selected. Data on pulmonary and extrapulmonary clinical presentation, radiologic patterns, laboratory findings, associated autoimmune diseases, treatments, and outcomes were analyzed. Frequency distribution and measures of central tendency were used to describe the cohort. Comparison between groups regarding qualitative variables was undertaken by chi-square or Fisher exact test, while T-test for independent variables was used to compare groups regarding continuous variables. IBM-SPSS v.22 was used for data analysis. RESULTS: PE was reported in 129 (48.6 %) episodes, DAH in 75 (28.3 %) episodes, and overlap (DAH plus PE) in 7 (2.6 %) episodes. Bronchoalveolar lavage (BAL) was performed in 35 (4.9 %) CAPS episodes, and lung pathology samples were obtained in 84 (10.5 %) episodes (including autopsies). A significant relationship was observed between DAH and laboratory features of thrombotic microangiopathy (TMA). A meaningful relationship was also found between triple antiphospholipid antibody positivity and pathological TMA (26.5 %) as well as hypocomplementemia and DAH (24 %). CONCLUSIONS: Pulmonary involvement may include both TMA and non-thrombotic inflammation, which can be differentiated into three patterns: PE, DAH with systemic TMA with hypocomplementemia or DAH without systemic TMA with/without hypocomplementemia.