Toll‐like Receptors (TLRs) are expressed by myeloid leukaemia cell lines, but fail to trigger differentiation in response to the respective TLR ligands

reported. In one study (Amoura et al, 2004), two patients with a simultaneous clinical picture of TTP and APS with LA, anticardiolipin, anti ADAMTS13 antibodies and ADAMTS13 low levels, were described. This association is controversial, and recent articles have recommended against the diagnosis of TTP in the presence of aPL antibodies (Porta et al, 2005). Other reports, when aPL antibodies and microangiopathic thrombosis has been observed, have suggested that aPL antibodies could be a consequence of the endothelial damage, but not a cause of the disease. (Asherson et al, 2008). There are isolated findings that could explain a sporadic relationship between APS and TTP. One such finding points out that, although ADAMTS13 deficiency and anti ADAMTS13 antibodies basically cause microcirculation thrombosis, there is a possibility that occasionally large vessel thrombosis in organs, such as the brain, could be a primary manifestation (Downes et al, 2004). In its turn, there is some evidence that the aPL activity creates an increased tissue factor production in extensive vascular regions (catastrophic APS) (Urbanus et al, 2008). It seems probable that systematic testing of ADAMTS13 and anti-ADAMTS13 antibodies in APS patients with neurological symptoms could identify cases of the underdiagnosed TTPAPS combination. Nevertheless, according to the findings of Austin et al (2008), the widespread prevalence of ADAMTS13 low activity and a variety of heterogeneous anti-ADAMTS13 antibodies in aPL positive patients without thrombotic events creates further questions.