Thomas Giner

Complement Factor H–Related Protein 1 Deficiency and Factor H Antibodies in Pediatric Patients with Atypical Hemolytic Uremic Syndrome

BACKGROUND AND OBJECTIVES This study evaluated the relevance of complement factor H (CFH)-related protein (CFHR) 1 deficiency in pediatric patients with atypical hemolytic uremic syndrome (aHUS) by evaluating both the frequency of deletions in CFHR1 and the presence of complement factor H (CFH) antibodies. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A total of 116 patients (mainly from central Europe) and 118 healthy blood donors were included from 2001 to 2012. The presence of CFHR1 gene deletions was determined in 90 pediatric patients with aHUS and 118 controls by an easy, fast, and cheap PCR assay; 100 patients with aHUS and 42 controls were tested for CFH antibodies by ELISA. Questionnaires were administered to evaluate the clinical and laboratory data. RESULTS Homozygous deletion in CFHR1 was detected in 32% of the patients with aHUS tested, compared with 2.5% of controls (P<0.001). CFH antibodies were present in 25% of the patients and none of the controls. CFH antibodies were detected in 82% of patients with homozygous CFHR1 gene deletion and in 6% of patients without. CFH antibody-positive patients with aHUS showed a significantly lower platelet nadir at disease onset and significantly less frequent involvement of the central nervous system than did antibody-negative patients. Antibody-positive patients also received plasma therapy more often. CONCLUSION Homozygous deletion in CFHR1 is strongly associated with occurrence of CFH antibodies in pediatric patients with aHUS. However, despite this apparent genetic disease predisposition, it cannot be considered an exclusive cause for aHUS. Initial presentation of Shiga toxin-negative HUS with severe thrombocytopenia and no central nervous system complications in pediatric patients is especially suspicious for CFH antibody aHUS.

A Large Family with a Gain-of-Function Mutation of Complement C3 Predisposing to Atypical Hemolytic Uremic Syndrome, Microhematuria, Hypertension and Chronic Renal Failure

BACKGROUND AND OBJECTIVES Atypical hemolytic uremic syndrome (aHUS) is associated with mutations in genes encoding complement-regulatory proteins factor H, I and B and membrane cofactor protein. Recently, heterozygous gain-of-function mutations in the complement C3 gene have been found in patients with aHUS. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A large family with a C3 R570Q mutation is described. Clinical and laboratory findings of carriers of the mutation and unaffected family members are reported. RESULTS The index patient suffered from recurrent aHUS at age 22 and developed end-stage renal failure. Of 24 family members, nine harbored the C3 R570Q mutation. Carriers showed reduced or borderline C3 levels. Arterial hypertension was found in six family members, microhematuria in five and chronic kidney disease stage 3 in two elderly carrier patients. Despite marked consumption of C3, serum terminal complement complex levels were not elevated in carriers compared with other family members. CONCLUSIONS The penetrance of the C3 R570Q mutation to induce aHUS is incomplete and lower compared with mutations in other genes predisposing to the disease. The mutation is possibly also associated with hypertension, hematuria and chronic kidney disease, all of which may represent consequences of long-term complement activation in the renal vasculature.

Extra-renal manifestations of complement-mediated thrombotic microangiopathies

Thrombotic microangiopathies (TMA) are rare but severe disorders, characterized by endothelial cell activation and thrombus formation leading to hemolytic anemia, thrombocytopenia, and organ failure. Complement over activation in combination with defects in its regulation is described in an increasing number of TMA and if primary for the disease denominated as atypical hemolytic-uremic syndrome. Although TMA predominantly affects the renal microvasculature, extra-renal manifestations are observed in 20% of patients including involvement of the central nerve system, cardiovascular system, lungs, skin, skeletal muscle, and gastrointestinal tract. Prompt diagnosis and treatment initiation are therefore crucial for the prognosis of disease acute phase and the long-term outcome. This review summarizes the available evidence on extra-renal TMA manifestations and discusses the role of acute and chronic complement activation by highlighting its complex interaction with inflammation, coagulation, and endothelial homeostasis.

Complement factor H-antibody-associated hemolytic uremic syndrome: pathogenesis, clinical presentation, and treatment.

The presence of circulating autoantibodies, primarily to complement factor H antibodies (CFH-Abs) in plasma characterizes the autoimmune form of atypical hemolytic uremic syndrome (aHUS). This acquired form of aHUS defines a distinct subgroup of aHUS patients, which requires diagnostic and treatment approaches in part different from those of the genetically defined forms. The mechanisms leading to CFH-Ab production and disease onset are not completely understood, but CFH-Ab HUS seems to be secondary to a combination of genetic predisposition and environmental factors. Early diagnosis of this specific aHUS entity is important, as prompt induction of plasma exchange and concomitant immunosuppression leads to a favorable outcome. Nevertheless, information on clinical features and outcome in children is limited. Here, we review the literature on the biological and clinical features of CFH-Ab HUS and discuss therapeutic options.

Diagnosis and Treatment of the Hemolytic Uremic Syndrome Disease Spectrum in Developing Regions

There has been rapid progress in the understanding of the pathophysiology of the hemolytic uremic syndrome (HUS) disease spectrum; thus, complex diagnostic and therapeutic requirements have emerged in parallel. Current recommendations for diagnosis and therapy were rapidly adapted from the prior skilled scientific groundwork. However, such recommendations can be realized only when highly specialized laboratories and sufficient financial resources are available. Thus, many recommendations are not feasible for patients living and working in developing countries. More than one-third of the worlds population has no access to essential drugs and more than half of this group lives in the poorest regions of Africa and Asia. From this perspective, distinct initial diagnostic and therapeutic recommendations, as well as international cooperations are needed to complete proper diagnostic work-ups in a stringent and cost-efficient manner and to enable patients to be adequately treated with available resources. However, while costs for complement-targeted drugs remain tremendously high, state-of-the-art treatment options remain unavailable for the vast majority of patients in developing areas.

Deficiency of the sphingosine-1-phosphate lyase SGPL1 is associated with congenital nephrotic syndrome and congenital adrenal calcifications

We identified two unrelated consanguineous families with three children affected by the rare association of congenital nephrotic syndrome (CNS) diagnosed in the first days of life, of hypogonadism, and of prenatally detected adrenal calcifications, associated with congenital adrenal insufficiency in one case. Using exome sequencing and targeted Sanger sequencing, two homozygous truncating mutations, c.1513C>T (p.Arg505*) and c.934delC (p.Leu312Phefs*30), were identified in SGPL1‐encoding sphingosine‐1‐phosphate (S1P) lyase 1. SGPL1 catalyzes the irreversible degradation of endogenous and dietary S1P, the final step of sphingolipid catabolism, and of other phosphorylated long‐chain bases. S1P is an intracellular and extracellular signaling molecule involved in angiogenesis, vascular maturation, and immunity. The levels of SGPL1 substrates, S1P, and sphingosine were markedly increased in the patients’ blood and fibroblasts, as determined by liquid chromatography–tandem mass spectrometry. Vascular alterations were present in a patients renal biopsy, in line with changes seen in Sgpl1 knockout mice that are compatible with a developmental defect in vascular maturation. In conclusion, loss of SGPL1 function is associated with CNS, adrenal calcifications, and hypogonadism.

Successful living-related renal transplantation in a patient with factor H antibody-associated atypical hemolytic uremic syndrome.

CFH‐Ab‐associated aHUS requires different diagnostic and therapeutic approaches and then the genetically defined aHUS forms. The risk of post‐transplant recurrence with graft dysfunction in CFH‐Ab aHUS is not well documented. It is suggested that recurrence can be expected if a significant CFH‐Ab load persists at the time of transplantation. A pretransplant procedure to reduce CFH‐Ab titer seems reasonable, but accurate recommendations are lacking. Whether further prophylactic interventions after transplantation are necessary has to be decided on an individual basis. We report the case of a late diagnosed CFH‐Ab HUS with initial ESRD and a successful living‐related renal transplantation over a post‐transplant period of four and a half years on the basis of a prophylactic pretransplant IVIG admission.

Severe visual loss caused by unrecognized malignant hypertension in a 15‐year‐old girl

A 15‐year‐old girl presented with acute bilateral loss of central visual acuity due to hypertensive retinopathy level IV. She was found to have unrecognized malignant arterial hypertension associated with end‐stage renal failure. At the time of diagnosis she also had severe left ventricular hypertrophy (LVH). Hypertension was successfully treated with combined anti‐hypertensive therapy, but renal function did not recover. The patient underwent successful kidney transplant 4 months later and over a period of 20 months hypertensive retinopathy and LVH gradually resolved. This report emphasizes the importance of routine measurement of blood pressure and describes the possible consequences of unrecognized arterial hypertension in children. Early diagnosis and appropriate treatment are necessary to avoid development and progression of target organ damage and promote better long‐term cardiovascular prognosis.

Therapeutic plasma exchange in children: One center's experience

Therapeutic plasma exchange (TPE) has evolved to an accepted therapy for selected indications. However, it is technically challenging in children. Moreover, data on safety and efficacy are mainly derived from adult series. The aim of this study was to review the procedure in the context of clinical indications, effectiveness, and safety.

Ethylene glycol intoxication presenting with high anion gap metabolic acidosis, acute kidney injury and elevated lactate

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