Is it possible to diagnose primary anti-phospholipid syndrome (PAPS) on the basis of renal thrombotic microangiopathy (PAPS nephropathy) in the absence of other thrombotic process?

The kidneys are a major target of PAPS. The histologic lesions of PAPS nephropathy are vascular; among them thrombotic microangiopathy (TMA) is the most characteristic. It is still not clear in the literature whether the nephropathy can be the unique manifestation of PAPS in the absence of other thrombotic processes; that is: do the renal microthrombotic lesions allow to make the diagnosis of PAPS in presence of anti-phospholipid antibodies (APA)? With this purpose we present three clinical cases. The first patient had severe hypertension C4 hypocomplementemia, thrombocytopenia, and mitralic valve insufficiency. LAC and anti-cardiolipin antibodies at high titre were positive. The histologic picture was characterized by basement membrane reduplication and arteriolar mucoid degeneration, which are features of early phase of TMA. The second patient had severe hypertension. The detection of anti-cardiolipin antibodies was performed several times and resulted positive three times, four months after the diagnosis as well. The renal histologic features were consistent with late lesions of TMA. The third patient had severe hypertension, rapidly progressive renal failure, tricuspidal valve insufficiency and two positive anti-phospholipid antibodies determinations three weeks apart (in two occasions anti-cardiolipin and in one occasion LAC as well were found). The renal lesions were characteristic for TMA. In conclusion we think that patients with TMA and antiphospholipid antibodies can be considered affected by PAPS, as the thrombotic process is represented by thrombosis in preglomerular arterioles, which leads to TMA.