Complement Activation and Thrombotic Microangiopathy Associated With Monoclonal Gammopathy: A National French Case Series.

RATIONALE & OBJECTIVE: Hemolytic uremic syndrome (HUS), a thrombotic microangiopathy (TMA) with kidney involvement, is a rare condition in patients with monoclonal gammopathy. In the absence of known causes of TMA, the role of complement activation in endothelial injury in patients with monoclonal gammopathy remains unknown and was the focus of this investigation. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: We studied the 24 patients in the French national registry of HUS between 2000 and 2020 who had monoclonal gammopathy without other causes of secondary TMA. We provide the clinical histories and complement studies of these patients. FINDINGS: Monoclonal gammopathy-associated TMA with kidney involvement is estimated to be 10 times less frequent than adult atypical HUS (aHUS) in the French national registry. It is characterized by severe clinical features, with 17 of 24 patients requiring dialysis at disease onset, and with median renal survival of only 20 months. TMA-mediated extrarenal manifestations, particularly cutaneous and neurological involvement, were common and associated with poor overall prognosis. Complement studies identified low C3, normal C4, and high soluble C5b-9 levels in 33%, 100%, and 77% of tested patients, respectively, indicating a contribution of the alternative and terminal complement pathways in the pathophysiology of the disease. Genetic abnormalities in complement genes known to be associated with aHUS were found in only 3 of 17 (17%) who were tested. LIMITATIONS: Retrospective study without comparison group; limited number of patients, limited available blood samples. CONCLUSIONS: Within the spectrum of TMA, TMA associated with monoclonal gammopathy represents a distinct subset. Our findings suggest that HUS associated with monoclonal immunoglobulin is a complement-mediated disease akin to aHUS.

Spectrum of Kidney Involvement in Patients with Myelodysplastic Syndromes.

INTRODUCTION: Myelodysplastic syndromes (MDS) are characterized by a high prevalence of associated autoimmune manifestations. Kidney involvement has been rarely reported in MDS patients. We report on the spectrum of kidney pathological findings in MDS patients. METHODS: We retrospectively identified MDS patients who had undergone a kidney biopsy between 2001 and 2019 in nine Swiss and French nephrology centres. RESULTS: Nineteen patients (median age 74 years [63-83]) were included. At the time of kidney biopsy, eleven (58%) patients had extra-renal auto-immune manifestations and sixteen (84%) presented with acute kidney injury. Median serum creatinine at diagnosis was 2.8 mg/dL [0.6-8.3] and median urinary protein to creatinine ratio was 1.2 g/g [0.2-11]. Acute tubulo-interstitial nephritis (TIN) was present in seven (37%) patients. Immunofluorescence study in one patient with acute TIN disclosed intense IgG deposits along the tubular basement membrane and Bowman's capsule. Other kidney pathological features included ANCA-negative pauci-immune necrotizing and crescentic glomerulonephritis (n = 3), membranous nephropathy (n = 2), IgA nephropathy (n = 1), IgA vasculitis (n = 1), immunoglobulin-associated membrano-proliferative glomerulonephritis type I (n=1), crescentic C3 glomerulopathy (n = 1), fibrillary glomerulonephritis (n = 1) and minimal change disease (n = 1). Eleven (58%) patients received immunosuppressive treatments, among whom one developed a severe infectious complication. After a median follow-up of 7 month [1-96], nine (47%) patients had chronic kidney disease stage 3 (n = 6) or 4 (n = 3) and five (26%) progressed to end-stage kidney disease. Three patients died. CONCLUSIONS: MDS are associated to several autoimmune kidney manifestations, predominantly acute TIN. MDS are to be listed among the potential causes of autoimmune TIN.

Aortic Dissection and Severe Renal Failure 6 Years After Kidney Transplantation.

We report the case of a patient with long-term history of hypertension, presenting with transient neurological disorders and severe graft failure several years after kidney transplantation. Cause of end-stage renal disease was hypertensive nephrosclerosis. Chronic hemodialysis lasted for 1 year. After transplantation and throughout follow-up, serum creatinine ranged from 200 to 230 µmol/L and maintenance immunosuppression included sirolimus and low-dose steroids. Six years after transplantation, the patient presented with right hip pain radiating to the lower back, transient aphasia, confusion, and hemiparesis. Surprisingly, progressive anuria was established requiring dialysis. After numerous nonconclusive investigations including renal histology, a contrast computed tomography scan discovered a Stanford B aortic dissection from the left common carotid artery and left subclavian artery to bilateral internal and external iliac arteries, including the right femoral artery. No surgical treatment was opted and hemodialysis, tight control of blood pressure and oral anticoagulation were established. Immunosuppression was lightened to low-dose steroids alone. After 8 months, chronic dialysis was stopped, and today, 22 months after the diagnosis of aortic dissection, the patient is doing well with a still functioning graft (creatinine, 377 µmol/L; modification of diet in renal disease-glomerular filtration rate, 15 mL/min), and without any other immunosuppression than low-dose steroids.

Prevention of lupus nephritis development in NZB/NZW mice by selective blockade of CD28.

Systemic lupus erythematosus (SLE) is a chronic systemic inflammatory disease. Autoantibodies (autoAbs) against double-stranded DNA (ds DNA), the hallmark of lupus, are produced and maintained by the interaction between auto-reactive B cells and CD4+ T cells. This interplay is controlled by the CD28/CD80-86/CTLA-4 axis. Here we investigated whether selective blockade of CD28-CD80/86 co-stimulatory interactions abrogates lupus nephritis development in a murine model of SLE. To this aim, NZB/NZW F1 mice were treated for 3 months, either with an anti-CD28 Fab' fragment or a control Fab'-IgG. The effect of CD28 blockade on lupus nephritis onset, survival, production of anti-ds DNA antibodies and costimulatory molecules was evaluated. CD28 blockade prevented the development of lupus nephritis and prolonged survival during the 3-month treatment and 12 weeks after. Furthermore, the production of anti-ds DNA autoAbs was decreased. Lastly, the protective effect of CD28 blockade was associated with increased intrarenal expression of the immunoregulatory molecule, Indoleamine 2, 3-dioxygenase, of the co-inhibitory receptor programmed cell-Death - 1 (PD-1) and of its ligand programmed death ligand - 1 (PDL-1).In conclusion, CD28 blockade prevented the development of lupus nephritis in NZB/NZW F1 mice. This immunomodulatory strategy is a promising candidate for SLE therapy in humans.

Vitamin D deficiency is an independent risk factor for PTDM after kidney transplantation.

An association between 25 hydroxyvitamin D [25(OH)D] deficiency and type 2 diabetes was observed in the general population. Such association was not investigated in kidney transplant recipients. We prospectively evaluated 444 patients following primary kidney transplantation between 2000 and 2010. The 25(OH)D level at transplantation was classified into three grades: deficiency (< 10 ng/ml), insufficiency (≥ 10 and < 30 ng/ml), and normal range (≥ 30 ng/ml). Time to Post-Transplant Diabetes Mellitus (PTDM) was defined according to the day of first prescription of hypoglycemic treatment. The 25(OH)D level at transplantation was deficient in 88 patients, insufficient in 264 patients, and normal in 92 patients. At 1 year post-transplantation, cumulative incidence of PTDM was 13.2%. Cox multivariate analysis indicated that 25(OH)D deficiency (≤ 10 ng/ml) at the time of transplantation was an independent risk factor for PTDM within the first year post-transplantation (HR = 2.41, 95% CI 1.01-5.75, P = 0.048), whereas insufficiency tended to increase this risk, although not significantly. 25(OH)D deficiency is a new independent risk factor for PTDM within the first year after kidney transplantation. Our study suggests that 25(OH)D may be a marker of general health in kidney transplant recipients and could alert clinicians for PTDM risk.