The mTORC pathway in the antiphospholipid syndrome

An immunogenomic exome landscape of triple positive primary antiphospholipid patients

Primary antiphospholipid syndrome is characterized by thrombosis and autoantibodies directed against phospholipids or associated proteins. The genetic etiology of PAPS remains unknown. We enrolled 21 patients with thromboembolic events associated to lupus anticoagulant, anticardiolipin and anti β2 glycoprotein1 autoantibodies. We performed whole exome sequencing and a systematic variant-based analysis in genes associated with thrombosis, in candidate genes previously associated with APS or inborn errors of immunity. Data were compared to public databases and to a control cohort of 873 non-autoimmune patients. Variants were identified following a state-of-the-art pipeline. Enrichment analysis was performed by comparing with the control cohort. We found an absence of significant HLA bias and genetic heterogeneity in these patients, including when testing combinations of rare variants in genes encoding for proteins involved in thrombosis and of variants in genes linked with inborn errors of immunity. These results provide evidence of genetic heterogeneity in PAPS, even in a homogenous series of triple positive patients. At the individual scale, a combination of variants may participate to the breakdown of B cell tolerance and to the vessel damage.

Renal Involvement in Antiphospholipid Syndrome

Antiphospholipid syndrome is a complex autoimmune disease, characterized by the presence of vascular thrombosis, obstetric, hematologic, cutaneous, and cardiac manifestations. Renal disease in patients with antiphospholipid syndrome was not recognized in the first descriptions of the disease, but later on, the renal manifestations of the syndrome have been investigated widely. Renal manifestations of antiphospholipid syndrome conform a wide spectrum of diverse renal syndromes. Hypertension is one of the most frequent, but less commonly recognized renal alteration. It can be difficult to control as its origin is renovascular. Renal vascular thrombosis can be arterial or venous. Other alterations are renal infarction and vascular thrombosis in arterial territories. Venous thrombosis can be present in primary and secondary antiphospholipid syndrome; it presents with worsening of previous proteinuria or de novo nephrotic syndrome, hypertension and renal failure. Antiphospholipid syndrome nephropathy is a vascular disease that affects glomerular tuft, interstitial vessels, and peritubular vessels; histopathology characterizes the renal lesions as acute or chronic, the classic finding is thrombotic microangiopathy, that leads to fibrosis, tubule thyroidization, focal cortical atrophy, and glomerular sclerosis. Antiphospholipid syndrome nephropathy can also complicate patients with systemic lupus erythematosus, and there is vast information supporting the worse renal prognosis in this group of patients with the classic histopathologic lesions. Treatment consists of anticoagulation, as for other thrombotic manifestations of antiphospholipid syndrome. There is some evidence of glomerulonephritis as an isolated lesion in patients with antiphospholipid syndrome. The most frequently reported glomerulonephritis is membranous; with some reports suggesting that immunosuppressive treatment may be effective. Patients with end stage renal disease commonly are positive for antiphospholipid antibodies, but it is not clear what is the role of aPL in this setting. Patients with vascular access may have complications in the presence of antibodies so that anticoagulation is recommended. Patients ongoing renal transplant with persistent antiphospholipid antibody positivity may have early and late graft failure.

Treatment of antiphospholipid syndrome beyond anticoagulation

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder marked by thrombosis and/or pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). At the present time, treatment is primarily focused on anticoagulation. However, there is increasing awareness of the mechanisms involved in APS pathogenesis, which has led to the trial of novel therapies targeting those mechanisms. Following a brief review of the etiopathogenesis of and current management strategies in APS, this paper focuses on the evidence for these potential, targeted APS treatments, e.g., hydroxychloroquine, statins, rituximab, belimumab, eculizumab, defibrotide, sirolimus, and peptide therapy.

Renal involvement in primary antiphospholipid syndrome

Antiphospholipid syndrome is an autoimmune disorder characterized by recurrent venous or arterial thrombosis and/or pregnancy-related problems associated with persistently elevated levels of antiphospholipid antibodies. The kidney is a major target organ in both primary and secondary antiphospholipid syndrome. This review describes several aspects of the renal involvement in the primary form of the syndrome, in particular the histological pattern of the so-called antiphospholipid syndrome nephropathy (APSN). APSN is a vascular nephropathy characterized by small vessel vaso-occlusive lesions associated with fibrous intimal hyperplasia of interlobular arteries, recanalizing thrombi in arteries and arterioles, and focal atrophy, a constellation of morphological lesions suggestive of primary antiphospholipid syndrome.

Catastrophic APS in the context of other thrombotic microangiopathies

The catastrophic antiphospholipid syndrome (CAPS) is a rare disease that affects 1 % of cases with antiphospholipid syndrome (APS). CAPS can mimic or overlap with different thrombotic diseases; many patients present with a microthrombotic storm or thrombotic microangiopathic hemolytic anemia (TMHA). Thus, the differential diagnosis of CAPS includes thrombotic thrombocytopenic purpura (TTP), typical and atypical hemolytic uremic syndrome (HUS), systemic infections, malignancies, pregnancy-related disorders, malignant hypertension, heparin-induced thrombocytopenia, and drug-induced thrombotic microangiopathies. Antiphospholipid antibody (aPL) positivity has been proposed as the clue in this differential diagnosis; however, aPL can also occur in healthy people and in those with infections or malignancies. Thus, the differential diagnosis of an aPL-positive patient presenting with a microthrombotic storm is broad; the workup should include a special attention to signs of infection and disseminated malignant disease, assessing the funduscopic signs of malignant hypertension, testing ADAMTS13 activity and anti-heparin-platelet factor 4 (HPF4) antibodies, and searching previous exposure to certain drugs. This article aims to review the main diseases included in the differential diagnosis of CAPS in the context of other thrombotic microangiopathies.

Ultrasonographic Evaluation of Resistive Index and Renal Artery Stenosis in Patients with Anti-Phospholipid Syndrome: Two Distinct Mechanisms?

Renal involvement in anti-phospholipid syndrome (APS) is still relatively unknown and probably underestimated. The described lesions consist of renal artery stenosis (RAS), venous renal thrombosis and glomerular lesions. The resistive index (RI) of intra-renal arteries, expression of the degree of vascular resistance, has been analyzed in different nephropathies and observed to be associated with functional parameters and some histologic features. In contrast, there are no studies on patients with APS. We evaluated the presence of a pathologic RI and RAS in a cohort of patients with APS. The study protocol included ultrasonographic assessment to measure the RI (RIs >0.7 were considered pathologic) and to determine the presence of RAS. We enrolled 36 patients with APS, 13 with primary APS and 23 with the form associated with systemic lupus erythematosus (SLE, secondary APS). As controls, we enrolled 10 anti-phospholipid antibody carriers, 10 patients with SLE without renal involvement and 14 age- and sex-matched healthy patients. A pathologic RI was identified in five patients with APS (13.9%) and in none of the anti-phospholipid antibody carriers (p = 0.00007). Four of the five (80%) patients with a pathologic RI had secondary APS. Three patients, all with primary APS, had RAS. The almost exclusive association of a pathologic RI with secondary APS and of RAS with primary APS suggests the involvement of two pathogenic pathways in the development of these different manifestations. The hypercoagulability status driven by APS could play a central role in the determination of RAS in patients with primary APS, whereas the activation of mTORC (mammalian target of rapamycin complex) pathways could be the pathogenic mechanism inducing development of a pathologic RI.

[What's new in internal medicine?]

This article focuses on current trends in various autoimmune diseases of interest for the dermatologist. In the antiphospholipid syndrome, many news: better characterization of the severe disease, involvement of the mTOR pathway in the vasculopathy-induced renal disease, and diversification of the therapeutic approaches: use of mTOR inhibitors and several biologics, new various antiplatelet and anticoagulants. In dermatomyositis, new autoantibodies are better characterized with a good correlation with clinical disease; the results of a large study on genetic predisposition to the disease are available. There are also some therapeutic innovations in systemic sclerosis: benefit of rituximab that seems well tolerated, the results of a large controlled European study about aggressive immunoablative chemotherapy followed by autologous stem cells have just been published, intralesional stem cells injections in the fingers of sclerodactylic patients. Finally, news in celiac disease that is constantly increasing and whose mild forms often have cutaneous manifestations, leading to diagnosis.