Atypical Hemolytic Uremic Syndrome: Differential Diagnosis from TTP/HUS and Management

A Rare Case of Atypical Hemolytic Uremic Syndrome Presenting as Chronic Interstitial Nephritis

Atypical hemolytic uremic syndrome commonly presents as rapidly progressive renal failure and is histologically characterized by thrombotic microangiopathy (TMA). TMA presenting with acute renal failure requires aggressive medical management. Here, we present a case of a 30-year-old man who presented with a history of accelerated hypertension and a strong family history of end-stage renal disease, in September 2023. Upon evaluation, he was found to have a creatinine level of 2 mg/dl, bland urine and normal-sized kidneys; a renal biopsy revealed chronic interstitial nephritis. Genetic analysis for autosomal dominant tubulointerstitial kidney disease and nephronophthisis yielded negative results. The patient was managed with antihypertensive medications. In January 2024, he was admitted with a history of confusion, headache, and alcohol binge. He had a blood pressure of 200/100 mmHg and had grade 3 hypertensive retinopathy. Laboratory tests revealed anemia with thrombocytopenia, bland urine, normal coagulation parameters, indirect hyperbilirubinemia, normal-sized kidneys on ultrasound, and elevated lactate dehydrogenase levels. MRI of the brain revealed symmetrical hyperintensities in bilateral cerebellum and the dorsal brainstem. Complement levels revealed low C3 levels and genetic analysis revealed a homozygous deletion in the complement factor H-related 3 (CFHR3) gene. The autoantibody for complement factor H was negative. The patient was managed conservatively with adequate blood pressure control. This case highlights the effects of complement dysregulation on the renal tubulointerstitium.

Pregnancy associated atypical hemolytic uremic syndrome presenting with preeclampsia with HELLP syndrome and following treatment with Eculizumab

Objectives

Pregnancy associated atypical hemolytic uremic syndrome (p-aHUS) is a rare condition of thrombotic microangiopathy (TMA) which causes an increase of fetal and maternal morbidity and mortality. It presents typically with a triad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia and acute progressive renal failure. Differential diagnoses of HELLP (Hemolysis, Elevated Liver enzymes, and Low Platelets) syndrome, preeclampsia, thrombotic thrombocytopenic purpura (TTP), and disseminated intravascular coagulation (DIC) syndrome must be considered. In the following case report, presented is a 32-year-old, 38 weeks pregnant Caucasian woman admitted to Eberswalde Hospital with signs of preeclampsia and HELLP Syndrome. Caesarean Section was performed due to HELLP syndrome and fetal distress. Acute renal failure occurs shortly after a successful delivery. After a diagnosis of p-aHUS is established, the patient was given Eculizumab, which yielded significant improvements.

Case presentation

A 32-year-old, 38 week pregnant Caucasian woman was admitted to Eberswalde Hospital with upper right abdominal pain. After a laboratory examination, a diagnosis of HELLP syndrome was established and a Caesarean Section was performed. The follow-up examination revealed deterioration of clinical signs with the patient experiencing dyspnea, oliguria, and oedema, as well as aggravation of laboratory values, ranging from severe thrombocytopenia, hemolytic anemia, liver injury, and acute kidney injury. After excluding other possible causes of TMA, a diagnosis of p-aHUS was established and a treatment with Eculizumab was administered. Clinical and laboratory signs of hemolysis and kidney functions were found to improve gradually after two administrations of Eculizumab. The patient was discharged after 20 days of hospitalization with significantly improved condition and hematological values.

Conclusions

A successful treatment of p-aHUS requires a comprehensive assessment and a prompt diagnosis, which can be confounded by multiple similar differential diagnoses. Treatment with Eculizumab was found to significantly improve the outcome of the patient, but more studies are required to decide on a standardized regiment for p-aHUS.

Pediatric Atypical Hemolytic Uremic Syndrome Advances

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder characterized by dysregulation of the alternate pathway. The diagnosis of aHUS is one of exclusion, which complicates its early detection and corresponding intervention to mitigate its high rate of mortality and associated morbidity. Heterozygous mutations in complement regulatory proteins linked to aHUS are not always phenotypically active, and may require a particular trigger for the disease to manifest. This list of triggers continues to expand as more data is aggregated, particularly centered around COVID-19 and pediatric vaccinations. Novel genetic mutations continue to be identified though advancements in technology as well as greater access to cohorts of interest, as in diacylglycerol kinase epsilon (DGKE). DGKE mutations associated with aHUS are the first non-complement regulatory proteins associated with the disease, drastically changing the established framework. Additional markers that are less understood, but continue to be acknowledged, include the unique autoantibodies to complement factor H and complement factor I which are pathogenic drivers in aHUS. Interventional therapeutics have undergone the most advancements, as pharmacokinetic and pharmacodynamic properties are modified as needed in addition to their as biosimilar counterparts. As data continues to be gathered in this field, future advancements will optimally decrease the mortality and morbidity of this disease in children.

Purtscher-Like Retinopathy Associated with Atypical Hemolytic Uremic Syndrome

A 25-year-old woman presented with acute bilateral blurred vision and history of headache, dizziness, and syncope for three days. Her visual acuity was 20/60 in both eyes. Fundoscopy revealed multiple bilateral peripapillary yellow-white patches like cotton wool spots, intraretinal hemorrhages and macular edema. The patient was diagnosed with Purtscher-like retinopathy based on the retinal findings and lack of trauma history. She was urgently admitted to the nephrology clinic due to thrombotic microangiopathy findings (hemoglobinemia, thrombocytopenia, and acute renal failure). After excluding thrombotic microangiopathy, the patient was diagnosed with atypical hemolytic uremic syndrome (aHUS) with the clinical and laboratory findings. Eculizumab treatment was added to hemodialysis and plasmapheresis therapy. Three months after starting treatment, retinal lesions regressed and visual acuity increased to 20/20 in both eyes. To the best of our knowledge, this is the first reported case of Purtscher-like retinopathy associated with aHUS.