Thrombotic microangiopathy due to acquired complement factor I deficiency in a male receiving interferon-beta treatment for multiple sclerosis

AIMS

Interferon-beta (IFNβ), the most widely prescribed medication for multiple sclerosis, is generally considered safe. Nevertheless, rare serious and/or life-threatening side effects have been reported such as thrombotic microangiopathy. A few mechanisms have been proposed to explain how interferon causes thrombotic microangiopathy, but immunological studies have been unable to pin this phenomenon down to a single pathophysiologic pathway. The aim of this article was to report a new mechanism explaining Interferon beta related thrombotic microangiopathy.

METHODS

We report thrombotic microangiopathy in a 28-year-old male receiving interferon-beta treatment for multiple sclerosis.

RESULTS

After three years of starting interferon beta therapy, the patient presented with malignant hypertension causing seizures, rapidly progressive renal failure requiring haemodialysis and haemolytic anaemia. Corticosteroid and plasma exchange sessions permitted haemolysis control. Nonetheless, the patient remained hemodialysis-dependent. Exploration of the complement system found a complement factor I deficiency whose activity normalized at the control carried out after 2 years.

CONCLUSION

IFNβ treatment may cause complement factor I deficit, which can lead to thrombotic microangiopathy and severe renal failure.

Cerebral Microangiopathy in Two Dogs with Cutaneous and Renal Glomerular Vasculopathy

Cutaneous and renal glomerular vasculopathy (CRGV) is an emerging disease in the UK, but its aetiology remains unclear. It is considered a thrombotic microangiopathy (TMA) in which the kidney and skin are the most commonly affected organs. We now document two cases of CRGV with brain lesions, which may have accounted for neurological signs displayed by these animals. The histopathological brain lesions were similar to TMA lesions in humans with thrombotic thrombocytopaenic purpura (TTP) and complement-mediated haemolytic uraemic syndrome (CM-HUS), in which the neurological signs are more associated with TMA than with any systemic disease or electrolyte imbalance. Fibrinoid necrosis in brain arterioles and associated lesions in these dogs were similar to those in human CM-HUS, indicating that the alternative complement pathway may play an important role in the pathophysiology of CRGV.

Clinicopathological features of cutaneous and renal glomerular vasculopathy in 178 dogs

BACKGROUND

One hundred seventy-eight dogs with cutaneous and renal glomerular vasculopathy (CRGV) were evaluated to further the understanding of the natural course of CRGV. CRGV, a form of thrombotic microangiopathy, can cause skin lesions and potentially acute kidney injury (AKI) with a high mortality rate.

METHODS

Cases were submitted from multiple practices from 2012 until June 2019. Clinical histories and laboratory data were reviewed to describe the features of CRGV.

RESULTS

Most cases (91%) occurred between November and May. Fifteen dogs (8.4%) with CRGV were in contact with another dog that developed skin lesions +/- AKI. Limb lesions were present on 144 dogs (80.9%) at presentation. Median time from appearance of a lesion to AKI was 3 days (range -4-45 days). Neurological signs occurred in 33 dogs (18.6%) including at presentation in 2 (1.1%). Systemic signs were present in 13 dogs prior to a skin lesion (7.3%). Non-steroidal anti-inflammatory drugs were prescribed prior to AKI identification in 92 of 170 dogs (54.1%). Thrombocytopenia was present in 115 of 137 (83.9%) of dogs.

CONCLUSION

The timeframe over which AKI may develop is longer than previously reported, neurological signs can be identified at presentation or during hospitalisation, and thrombocytopenia is even more common than previously reported.

Does Outcome/Survival of Patients With Myelodysplastic Syndromes Should Be Predicted by Reduced Levels of ADAMTS-13? Results From a Pilot Study

INTRODUCTION

Von Willebrand factor (vWF) cleaving protease ADAMTS-13 has a key role for maintaining normal size of vWF. A deficiency or dysfunction of vWF cleaving protease is associated with ultra large vWF multimers and thrombotic microangiopathy. Patients with cancers have reduced levels of vWF cleaving protease. In this pilot study, we have evaluated whether or not deficiencies of ADAMTS-13 were present in myelodysplastic syndromes (MDS). Moreover, we assessed if a reduction in basal levels of ADAMTS-13 may play a role in the prognosis of MDS.

PATIENTS AND METHODS

We measured and compared the levels of vWF cleaving protease ADAMTS-13 in 100 patients with MDS and 35 healthy controls. Patients were divided into 2 groups according to the International Prognostic Scoring System: group I consisting of 44 patients with low-risk MDS and group II of 56 patients with high-risk MDS. Patients with high-risk and low-risk MDS presented significantly lower levels of ADAMTS-13 than controls (P < .001 and P = .0177, respectively). High-risk patients had significantly lower levels of ADAMTS-13 when compared with the low-risk group (P < .001).

RESULTS

We found that reduced levels of ADAMTS-13 have a relationship with overall survival (P < .001). Statistical analysis showed that ADAMTS-13 correlates with cytogenetics (P < .001) and a tendency of slight correlation with platelet count and basal levels of ADAMTS-13 (R, 0.35; P value, 0.001). Moreover, we found that levels of ADAMTS-13 have correlation with response to treatment (P < .001).

CONCLUSIONS

ADAMTS-13 in MDS might represent a surrogate marker of prognosis, response to therapy, or disease progression. Further studies are needed.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

The role of complement in Streptococcus pneumoniae-associated haemolytic uraemic syndrome

BACKGROUND

Atypical forms of haemolytic uraemic syndrome (aHUS) include HUS caused by defects in the regulation of alternative complement pathway and HUS linked to neuraminidase-producing pathogens, such as Streptococcus pneumoniae. Increasing data support a pathogenic role of neuraminidase in the development of S. pneumoniae-associated haemolytic uraemic syndrome (SP-HUS), but the role of complement has never been clarified in detail. Therefore, we aimed to investigate whether the pathologic complement profile and genetic risk factors of aHUS are present in patients with SP-HUS.

METHODS

Enrolling five patients with SP-HUS classical and alternative pathway activity, besides C3, C4, factors H, B, I and anti-factor H autoantibody levels were determined. The coding regions of CFH, CFI, CD46 (MCP), THBD, C3 and CFB genes were sequenced and the copy number of CFI, CD46, CFH and related genes were also analyzed.

RESULTS

We found that in the acute phase samples of SP-HUS patients, complement components C4, C3 and activity of the classical and alternative pathways were decreased, indicating severe activation and complement consumption, but most of these alterations normalized later in remission. Three of the patients carried mutations and risk haplotypes in complement-mediated aHUS associated genes. The identified mutations include a previously published CFI variant (P50A) and two novel ones in CFH (R1149X) and THBD (T44I) genes.

CONCLUSIONS

Our results suggest that severe complement dysregulation and consumption accompany the progress of invasive pneumococcal disease (IPD)-associated SP-HUS and genetic variations of complement genes may contribute to the development of this complication in a proportion of the affected patients.

Thrombotic microangiopathy: a role for magnesium?

Despite advances in more recent years, the pathophysiology and especially treatment modalities of thrombotic microangiopathy (TMA) largely remain enigmatic. Disruption of endothelial homeostasis plays an essential role in TMA. Considering the proven causal association between magnesium and both endothelial function and platelet aggregability, we speculate that a magnesium deficit could influence the course of TMA and the related haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura. A predisposition towards TMA is seen in many conditions with both extracellular and intracellular magnesium deficiency. We propose a rationale for magnesium supplementation in TMA, in analogy with its evidence-based therapeutic application in pre-eclampsia and suggest, based on theoretical grounds, that it might attenuate the development of TMA, minimise its severity and prevent its recurrence. This is based on several lines of evidence from both in vitro and in vivo data showing dose-dependent effects of magnesium supplementation on nitric oxide production, platelet aggregability and inflammation. Our hypothesis, which is further amenable to assessment in animal models before therapeutic applications in humans are implemented, could be explored both in vitro and in vivo to decipher the potential role of magnesium deficit in TMA and of the effects of its supplementation.

Shiga toxin pathogenesis: kidney complications and renal failure

The kidneys are the major organs affected in diarrhea-associated hemolytic uremic syndrome (D(+)HUS). The pathophysiology of renal disease in D(+)HUS is largely the result of the interaction between bacterial virulence factors such as Shiga toxin and lipopolysaccharide and host cells in the kidney and in the blood circulation. This chapter describes in detail the current knowledge of how these bacterial toxins may lead to kidney disease and renal failure. The toxin receptors expressed by specific blood and resident renal cell types are also discussed as are the actions of the toxins on these cells.