Eculizumab, a successful treatment for atypical postpartum hemolytic-uremic syndrome: a case report / Eculizumab, un tratamiento exitoso en el síndrome hemolítico-urémico atípico puerperal: un caso clínico

Atypical hemolytic-uremic syndrome (aHUS) is a rare entity characterized by the association of acute kidney failure, thrombocytopenia and microangiopathic hemolytic anemia due to the dysregulation of the alternative pathway of the complement system. It is included within the thrombotic microangiopathies. The following aHUS was developed in the immediate puerperium in the context of severe preeclampsia. The patient was a primiparous woman of 30+1 weeks who required hospitalization for anticonvulsant and hypotensive treatment, and who underwent an emergency cesarean section due to a pathological cardiotocographic pattern. 36 hours after delivery, the patient presented with sudden dyspnea and cognitive deterioration, progressing in a few hours to renal and multiorgan failure. Blood test showed severe anemia, thrombopenia and hypertransaminemia. In view of the fast evolution and severity, it was decided to treat with Eculizumab, although the scientific evidence was very poor. Aside from the supportive treatment performed in the Intensive Care Unit, the patient was successfully treated with Eculizumab, with favorable evolution over the following months and restoration of kidney function, although need for chronic hypotensive treatment remained.

El síndrome hemolítico-urémico atípico (SHUa) es una entidad rara caracterizada por la asociación de insuficiencia renal aguda, trombocitopenia y anemia hemolítica microangiopática debido a la desregulación de la vía alternativa del sistema del complemento. Se incluye dentro de las microangiopatías trombóticas. Se presenta un SHUa que se desarrolló en el puerperio inmediato en el contexto de una preeclampsia grave. La paciente era una primípara de 30+1 semanas que requirió hospitalización para tratamiento anticonvulsivo e hipotensor, y a la que se le practicó una cesárea de urgencia por un patrón cardiotocográfico patológico. A las 36 horas del parto, la paciente presentó una disnea súbita y un deterioro cognitivo progresivo, que evolucionó en pocas horas a un fallo renal agudo y multiorgánico. La analítica mostró anemia severa, trombopenia e hipertransaminemia. Ante la rápida evolución y gravedad, se decidió tratar con Eculizumab, aunque la evidencia científica era escasa. Aparte del tratamiento de soporte realizado en la Unidad de Cuidados Intensivos, la paciente fue tratada con éxito con Eculizumab, con evolución favorable en los meses siguientes y restablecimiento de la función renal, aunque se mantuvo la necesidad de tratamiento hipotensor crónico.

Biomarcadores y blancos moleculares del complemento en el diagnóstico de las microangiopatías trombóticas / Complement biomarkers and molecular targets in the diagnosis of thrombotic microangiopathies / Biomarcadores e alvos moleculares do complemento no diagnóstico das microangiopatias trombóticas

Resumen El sistema del complemento juega un papel central en la inmunidad innata, es una línea de defensa contra patógenos y participa en la homeostasis. La activación anormal del complemento contribuye al desarrollo de patologías de variable severidad, tanto inmunológicas y hematológicas como renales. Entre ellas, las microangiopatías trombóticas (MAT) representan un grupo de enfermedades raras con manifestaciones clínicas comunes caracterizadas por anemia hemolítica no inmune, trombocitopenia y daño de órgano(s) blanco. Si bien la clasificación de las MAT sigue siendo desafiante y no ha sido internacionalmente estandarizada, la descripción de entidades asociadas a anomalías del complemento fue comprobada con la eficiencia de la terapia anticomplemento en los pacientes. Las herramientas de diagnóstico desarrolladas en las últimas décadas son esenciales actualmente para diferenciar las MAT más características del grupo; esto es, la púrpura trombótica trombocitopénica (PTT) y el síndrome urémico hemolítico (SUH). En el presente trabajo se presenta una revisión del funcionamiento del sistema del complemento en condiciones fisiológicas, para poder explicar luego cuáles son las alteraciones del sistema implicadas en el desarrollo de las MAT y describir las herramientas disponibles para detectarlas en el laboratorio.

Abstract The complement system plays a crucial role in the innate immune response, being the first-line defense against pathogens and regulating homeostasis. Uncontrolled complement activation can cause immunologic, hematologic as well as renal syndromes of variable severity. Among them, thrombotic microangiopathies (TMA) represent a group of rare diseases characterised by similar clinical manifestations such as microangiopathic hemolytic anemia (MAHA), peripheral thrombocytopenia and organ injury. Although TMA classification is still challenging and no international consensus has been reached, complement-associated disorders have been described thanks to the efficiency of anti-complement therapy in patients. Diagnostic tools developed in the last decades are essential to differentiate the two most well characterized TMA: thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). This review will describe how the complement system works in physiological conditions in order to explain how complement abnormalities are involved in TMA, and finally how to detect those anomalies using laboratory tests.

Resumo O sistema do complemento desempenha um papel central na imunidade inata, sendo uma linha de defesa contra patógenos e participando da homeostase. A ativação anormal do complemento contribui para o desenvolvimento de patologias de gravidade variável, como imunológicas, hematológicas e renais. Entre elas, as microangiopatias trombóticas (MAT) representam um grupo de doenças raras com manifestações clínicas comuns caracterizadas por anemia hemolítica não imune, trombocitopenia e lesão de órgão(s) alvo. Embora a classificação das MAT continue sendo desafiadora e não tenha sido padronizada internacionalmente, a descrição de entidades associadas a anomalias do complemento foi comprovada com a eficiência da terapia anticomplemento nos pacientes. As ferramentas de diagnóstico desenvolvidas nas últimas décadas são atualmente essenciais para diferenciar as MAT mais características do grupo, que são a púrpura trombocitopênica trombótica (PTT) e a síndrome hemolítica urêmica atípica (SHU). Neste trabalho, é apresentada uma revisão do funcionamento do sistema de complemento em condições fisiológicas, a fim de explicar posteriormente quais são as alterações do sistema compreendidas no desenvolvimento das MAT, e descrever as ferramentas disponíveis para detectá-las em laboratório.

Síndrome hemolítico urémico atípico / Atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy, characterized by microangiopathic hemolytic anemia, thrombocytopenia and renal involvement. It causes end stage renal disease requiring dialysis in most affected patients. It mainly affects young adults (contrary to what was thought years ago). When aHUS is primary, the cause is a genetic mutation in the alternative complement pathway. Instead, secondary aHUS is caused by external factors that trigger the disease by themselves or in combination with a genetic vulnerability. The type of mutation determines the severity of the disease, prognosis, response to therapy and renal transplantation. Advances in the understanding of renal diseases associated with complement defects and the development of specific biologic therapies changed the course of this disease. Eculizumab is internationally approved for the treatment of primary aHUS. Its inhibitory action on the complement cascade leads to hematologic remission and restoration of renal function. We present a review of aHUS detailing its etiology, pathogenesis, clinical presentation, diagnosis and treatment.

Síndrome hemolítico urémico atípico en tratamiento con eculizumab: casos clínicos / Atypical hemolytic uremic syndrome: report of two cases treated with Eculizumab

Hemolytic uremic syndrome (HUS) is a type of thrombotic microangiopathy where organic damage predominates in the kidney. Atypical HUS (aHUS) is a rare disease that affects young adults and causes terminal chronic renal failure ending in dialysis, in most cases. It also recurs after kidney transplantation. aHUS is associated with genetic defects of the alternative complement pathway or its activation by other factors such as drugs, autoimmune diseases, infections, malignant hypertension and ischemia-reperfusion. We report two women aged 17 and 25 years old with catastrophic aHUS. In both cases, complement amplifying factors (drugs and infections) were added and acted on a genetic vulnerability to precipitate complement activation and produce aHUS. Both patients developed terminal renal failure and had to undergo hemodialysis. Fortunately, after a broad etiological study, it was possible to make the diagnosis of aHUS and start treatment with Eculizumab, a monoclonal antibody that changed the natural history of aHUS. It inhibits complement activity controlling microangiopathy and preventing the development of end-stage renal disease. It also improves the success rate in kidney transplantation. In the case of our patients, both discontinued dialysis after chronic treatment with Eculizumab.