SSB and systemic lupus erythematosus: Muznay et al found that in APS due to systemic lupus erythematosus, the complete loss of aPL positivity after thrombosis was 41% for IgG aCL, 51% for IgM, 50% for IgA, and 20% for LA.[12] aPLs may also be transient and occur in low titers in patients with APS and COVID-19.