Primary Hyperaldosteronism: A Rare Cause of Malignant Hypertension with Thrombotic Microangiopathy in a Kidney Transplant Recipient

Thrombotic microangiopathy (TMA) is a rare disease that presents with haemolysis and organ damage. The kidney is one of the main affected organs, and TMA is associated with serious complications and increased mortality. In transplanted patients, TMA is even less common and has a variety of possible causes, including thrombotic thrombocytopenic purpura (TTP) and haemolytic-uremic syndrome (HUS), infections, drugs, autoimmune disease, tumours, and malignant hypertension. Transplant-related causes, such as antibody-mediated rejection, calcineurin inhibitors, and viral infections, need to be considered as well. The authors report a rare case of TMA in a kidney transplant recipient, whose investigation revealed malignant hypertension secondary to primary hyperaldosteronism.

A Challenging Case of Atypical Hemolytic Uremic Syndrome in a Young African American Patient

Background It is known that malignant hypertension (mHTN) and thrombotic microangiopathy (TMA) commonly coexist. Deciding which phenomenon preceded the other remains a clinical dilemma, specifically in African American patients. However, making that determination is of utmost importance because the management will be different, and that can have dramatic effects on prognosis and outcomes. Herein, we report a case of atypical hemolytic uremic syndrome (aHUS) presenting as mHTN. Case Presentation A 35-year-old African American male with known history of hypertension, presented with nausea, vomiting, and diarrhea for four days. He also reported fatigue and exertional shortness of breath. Upon presentation, his blood pressure was 260/160 mmHg, otherwise physical exam was unremarkable. Initial work up showed hemoglobin of 8.8 g/dL (baseline 13.5), platelet count of 21,000/mL (baseline 250,000), serum creatinine of 16.99 mg/dL (baseline 0.99), MCV (84 fl), increased reticulocyte production index (3.58), increased LDH (1709 U/L), undetectable haptoglobin, and numerous schistocytes on peripheral blood smear. He was admitted as a case of hypertensive emergency and TMA. IV labetalol and hemodialysis were started. Given his gastrointestinal symptoms; stool for Shigella and E.Coli O157:H7 were checked and they were negative. Given the severity of his hematologic derangements and difficult to control blood pressure, we decided to proceed with renal biopsy to rule out primary aHUS which showed thrombotic microangiopathy, global glomerulosclerosis, moderate interstitial fibrosis and tubular atrophy suggestive of aHUS or rheumatologic disorders like systemic sclerosis and arguing against malignant HTN as the sole player. ANA and anti-Scl-70 antibodies were negative. Final impression was aHUS by exclusion, and patient received meningococcal vaccines (Menactra and Bexsero) in preparation to start eculizumab. aHUS genetic panel was sent which came back equivocal as it showed mutations of unknown significance (homozygous missense mutation in the MASP2 gene and 2 heterozygous mutations in the C2 gene). He was started on eculizumab 900 mg weekly for 4 weeks then 1200 mg biweekly starting week 5. He was seen in the office 2 months after initial presentation and receiving 5 doses of Eculizumab. His kidney function showed improvement with > 2 liters of urine output daily, blood pressure was better controlled. A decision by nephrology was made to give him a break from dialysis and remains dialysis-free a year later. Discussion aHUS is a rare disorder with an estimated prevalence of seven per one million children in Europe. It causes uninhibited activation of complement factors that leads to renal endothelial damage and activation of coagulation cascade leading to TMA. The diagnosis of aHUS requires the fulfillment of the classical triad (microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure) with a positive gene mutation or antibodies to complement factors. However, absence of these mutations or antibodies, as in the presented case, do not exclude the diagnosis. The early diagnosis of aHUS is necessary for treatment with eculizumab, a monoclonal antibody against C5 to block the terminal complement cascade. Kidney biopsy can be helpful in equivocal cases especially if it shows only the typical changes of malignant hypertension which essentially rules out aHUS. Hypertension with concurrent TMA is treated with strict BP control which is often enough to resolve TMA features and restores renal function, at least partially. On the contrary, aHUS causing severe HTN needs more sophisticated testing and blockade of the terminal complement component to improve outcome; that's why the distinction of which one is the primary process is of utmost importance. Our case emphasizes the importance of having low threshold for testing for aHUS in patients with mHTN and TMA, especially in African American patients where malignant HTN is known to happen more commonly, and to notice the subtle hints that may help in this distinction, such as profound hemolysis or thrombocytopenia out of proportion to what one would expect from mHTN alone. Early recognition of aHUS may save a patient's kidney. Disclosures No relevant conflicts of interest to declare.

RNA sequencing reveals induction of specific renal inflammatory pathways in a rat model of malignant hypertension

In malignant hypertension, far more severe kidney injury occurs than in the “benign” form of the disease. The role of high blood pressure and the renin–angiotensin–aldosterone system is well recognized, but the pathogenesis of the renal injury of malignant hypertension (MH) remains incompletely understood. Using the rat model of two-kidney, one-clip renovascular hypertension in which some but not all animals develop MH, we performed a transcriptomic analysis of gene expression by RNA sequencing to identify transcriptional changes in the kidney cortex specific for MH. Differential gene expression was assessed in three groups: MH, non-malignant hypertension (NMH), and normotensive, sham-operated controls. To distinguish MH from NMH, we considered two factors: weight loss and typical renovascular lesions. Mean blood pressure measured intraarterially was elevated in MH (220 ± 6.5 mmHg) as well as in NMH (192 ± 6.4 mmHg), compared to controls (119 ± 1.7 mmHg, p < 0.05). Eight hundred eighty-six genes were exclusively regulated in MH only. Principal component analysis revealed a separated clustering of the three groups. The data pointed to an upregulation of many inflammatory mechanisms in MH including pathways which previously attracted relatively little attention in the setting of hypertensive kidney injury: Transcripts from all three complement activation pathways were upregulated in MH compared to NMH but not in NMH compared with controls; immunohistochemistry confirmed complement deposition in MH exclusively. The expression of chemokines attracting neutrophil granulocytes (CXCL6) and infiltration of myeloperoxidase-positive cells were increased only in MH rats. The data suggest that these pathways, especially complement deposition, may contribute to kidney injury under MH. Key messages The most severe hypertension-induced kidney injury occurs in malignant hypertension. In a rat model of malignant hypertension, we assessed transcriptional responses in the kidney exposed to high blood pressure. A broad stimulation of inflammatory mechanisms was observed, but a few specific pathways were activated only in the malignant form of the disease, notably activation of the complement cascades. Complement inhibitors may alleviate the thrombotic microangiopathy of malignant hypertension even in the absence of primary complement abnormalities.

Abstract P182: Microangiopathic Complications In Malignant Hypertension: An Under-appreciated Form Of Target Organ Damage

Fig 1: Summary of Malignant Hypertension Studies having Microangiopathic Complications along with Forest Plot Microangiopathic Complications in Malignant Hypertension: An underappreciated form of Target Organ Damage Background: Renal thrombotic microangiopathy is a clinically important complication of malignant hypertension (MHT), but its incidence in MHT has been sparsely studied. Our aim was to study the incidence of microangiopathic changes (MaC) in MHT. Methods: We searched Google Scholar database studies directly reporting MaC (mentioning either microangiopathic hemolytic anemia or thrombotic angiopathy) in presence of MHT. We used OpenMeta[Analyst] for the pooled analysis. Results: From 1967 to 2019, 9 studies were included. Maximum likelihood random-effects method showed pooled proportion estimate of having MaC in MHT to be 0.4 (95 CI: 0.3, 0.5; p<0.1). Significant heterogeneity with I 2 =82.56%, p <0.1 was found. Subgroup analysis showed pooled proportion of MaC in MHT to be 0.5 (95 CI: 0.4,0.7, p<0.1) for studies before 2000; whereas 0.2 (95 CI: 0.2, 0.3, p<0.1) for studies after 2000. Sex-wise distribution was reported in 7 studies, risk ratio of having MaC in MHT in female was found to be 1.24 compared to male. Conclusion: Our analysis suggests decreasing incidence of MaC in MHT over the past couple of decades and increased risk of this complication in females, although significant heterogeneity exists among studies reporting microangiopathic changes in malignant hypertension. More prospective observational studies are needed to better define the epidemiology of the hematological changes that occur in MHT since they have important therapeutic implications.

An unusual case of delayed and recurrent bleeding after renal biopsy in a patient with malignant hypertension

We report a 35-year-old Asian man who presented with symptomatic malignant hypertension with complications of acute kidney injury, thrombocytopenia and microangiopathic haemolytic anemia. A renal biopsy done led to recurrent bleeding needing repeated embolization. We highlight the importance of continued monitoring for post biopsy bleeding even weeks after the biopsy for high-risk cases and discuss the aspects of prevention of severe post biopsy bleeding. Keywords: Renal biopsy; Malignant hypertension; Embolization; Desmopressin.