[Efficacy of eculizumab in a case of pregnancy-associated aHUS]. / Efficacia di eculizumab in un caso di SEU atipica associata alla gravidanza.

Pregnancy-associated thrombotic microangiopathy (TMA) is a rare condition, but it is burdened by a significant perinatal and maternal morbidity as well as mortality. We describe the case of a 33-year-old woman, who developed a TMA at the 36th week of gestation characterized by increased LDH, haptoglobin consumption, schistocytes, thrombocytopenia and acute renal failure requiring dialysis. There were not gestational hypertension nor proteinuria until the day of hospitalization. ADAMTS 13 deficiency was ruled out and the patient did not have diarrhea. She was initially treated with caesarean section, plasma infusion and plasmapheresis with no benefit. Five days after the onset of TMA, a temptative diagnosis of atypical uremic syndrome (aHUS) was made and the patient was switched to eculizumab. Antibiotic prophylaxis and anti-meningococcal A,B, C, W135 and Y vaccination was performed. TMA rapidly resolved and renal function completely recovered. The newborn had a normal perinatal course. A complement dysregulation was ruled out by testing for mutations on CFH, CFHR3-R1, CFI, MCP, CFB, C3 and for anti CFH antibodies. In conclusion the differential diagnosis of aHUS with HELLP syndrome is often not straightforward. The severity and persistence of TMA, the high mortality associated to peripartum TMA and the risk for irreversible kidney failure require an early therapeutic decision as to the use of eculizumab.

[Lymphomatous renal involvement]. / Il coinvolgimento renale nei linfomi.

The incidence of lymphomas, especially non-Hodgkin's lymphoma (NHL), has shown a steady increase over the last decades. At the same time, the prognosis has improved. Given the longer survival of lymphoma patients, pathological manifestations related to malignancy might become more frequent. In this setting, the kidney is one of the most important solid organs affected by direct or indirect lymphomatous involvement. Kidney involvement can be related to obstruction or treatment-induced toxicity, but more intriguing are 1) direct infiltration (NHL); 2) renal malignancies in patients affected by Hodgkin's disease or NHL; 3) associated glomerular diseases. Primary infiltration is rarely seen, while secondary infiltration is described most frequently in autopsy series, even in the absence of renal failure. These alterations may mimic glomerular and/or interstitial disease. The association with kidney malignancies, mostly renal cell carcinoma but also urothelial tumors in Hodgkin''s disease, is higher in lymphoma patients than in the general population: the relative risk at 10 years is about 1.5. Glomerulonephritis is described in patients with Hodgkin's disease or NHL; in the former minimal change disease is most frequent, in the latter the glomerular pattern varies widely. Glomerulonephritis can precede, be concurrent with, or follow lymphoma manifestations. Renal biopsy is often needed in this setting.

Structure-activity relationships of low molecular weight heparins expose to the risk of achieving inappropriate targets in patients with renal failure.

Heparins are used in "therapeutic doses" for systemic anticoagulation to treat patients who have confirmed venous thromboembolism, or in "prophylactic doses "for the prevention of venous thromboembolism: they are generally lower doses and are employed once a day. Structure-function relationships are strongly influenced by the chain length of the molecules. In fact, unfractionated heparin (UFH) binds to ATIII lysine site leading to a conformational change of the ATIII arginine reactive centre able to create a covalent binding to the active centre serine of thrombin in a ternary complex formation composed by heparin, ATIII and thrombin. On the other side, low molecular weight heparins (LMWHs) are too short to be able to form this ternary complex, and mainly exert their anticoagulant effect by binding the factor Xa, always via ATIII. Lastly, the short unique pentasaccharidic sequence which is crucial for heparin's activity and has been recently synthesized as Fondaparinux, only acts via the formation of the high affinity ternary complex with ATIII-factor Xa. Due to their structure-function relationships, LMWHs cannot be monitored by conventional coagulation test used for monitoring UFH and need more specific anti-factor Xa activity determinations, but monitoring has been considered unnecessary in the general population due to a predictable dose/effect ratio. However, a disturbing rise of bleeding complications in patients with renal failure treated with LMWH has been published in the last years, that is explained by the accumulation of LMWHs in this setting, due the consequences of structure-metabolisms relationships of the small members of the heparin's family. In this context, physicians are often left to a "best guess" method of empiric dose adjustment, which is at risk of achieving inappropriate targets, with a percentage of values above and below target of 51% and 34%, respectively, depending on LMWHs dosage, body mass index and renal function. Without anti-Xa activity monitoring, the quality of care delivered in the setting of renal failure is poor, as over-prophylaxis can result in potentially dangerous anticoagulation, while under-prophylaxis can result in life-threatening thrombosis.