Moyamoya vasculopathy in a child after hemolytic uremic syndrome: a possible etiopathogenesis

A case of Moyamoya disease complicated by aHUS in a patient with a history of marginal zone B-cell lymphoma: lightning strikes thrice?

Atypical haemolytic uraemic syndrome (aHUS) is a rare, acquired thrombotic microangiopathy, mediated by complement activation, in very sick patients. Moyamoya is similarly a rare disease in which stenosis or occlusion of segment(s) of the anterior cerebral circulation leads to the formation of many thin collaterals. Other reports have described an association between HUS and Moyamoya disease in the paediatric population. However, this case study presents the exceptionally rare presentation of an adult with aHUS and Moyamoya disease in a patient who was treated with rituximab for marginal zone B-cell lymphoma.

Macrovascular involvement in a child with atypical hemolytic uremic syndrome

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a disorder of the complement system which leads to thrombotic microangiopathy. It is caused by either acquired or hereditary defects in the activation or regulation of the alternative complement pathway and is therefore considered to be a disease of local complement dysregulation in microvasculature with predominantly renal involvement. However, extrarenal manifestations are observed in approximately one-fifth of aHUS patients, with the myocardium and central nervous system (CNS) being involved most often. Additionally, there have been a few reports of aHUS with cerebral artery stenoses or periphereal gangrene, suggesting the possibility of 'macrovascular' involvement in aHUS.

CASE-DIAGNOSIS/TREATMENT

We present a child with early onset aHUS and a C3 gain-of-function mutation who developed cerebral artery stenoses, leading ultimately to death due to a massive stroke 9 days after successful renal transplantation under prophylactic eculizumab treatment. Similar cases described in the literature are also briefly summarized.

CONCLUSIONS

The disease course in our patient with aHUS confirms that dysregulated complement activation can induce arterial steno-occlusive lesions in the absence of acute episodes of HUS. Further studies are required to document the frequency of such macrovascular complications and the role of eculizumab treatment in preventing their development and progression.

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.

Congenital thrombotic thrombocytopenic purpura associated with moyamoya syndrome in a 3-year-old girl: a case report

A 3-year-old girl who presented with anemia, thrombocytopenia, and recurrent strokes is described. The cerebral angiography revealed moyamoya vasculopathy. Her younger brother also had anemia and thrombocytopenia but no neurologic abnormalities. Both children had severe deficiency of ADAMTS13 (A Disintegrin And Metalloprotease with Thrombospondin like domain activity) confirming the diagnosis of congenital thrombotic thrombocytopenic purpura. The children responded well to regular fresh-frozen plasma infusions. This report expands the spectrum of hematologic diseases associated with moyamoya syndrome. Unexplained thrombocytopenia, especially in the presence of neurologic symptoms, should prompt an evaluation for ADAMTS13deficiency. The diagnosis has significant implications not only for therapy but also for genetic counseling.

Moyamoya in a child treated with interferon for recurrent osteosarcoma

Moyamoya is a cerebral vasculopathy of unknown etiology rarely described as a late effect after the treatment of childhood cancer. We describe a 12-year-old female who developed moyamoya after the completion of systemic chemotherapy, surgery, and adjuvant interferon alpha for osteosarcoma with pulmonary metastases. Given the importance of characterizing late effects after the treatment of childhood cancer, the potential role of interferon alpha in the development of moyamoya is discussed.

Non-atheromatous arterial stenoses in atypical haemolytic uraemic syndrome associated with complement dysregulation

BACKGROUND

A child, who presented atypical haemolytic uraemic syndrome (aHUS) at the age of 1 month, developed cerebral ischaemic events at the age of 10 years.

RESULTS

Stenoses of both carotid arteries, left subclavian and vertebral arteries, several intracranial, right humeral, several coronary, and all pulmonary arteries were demonstrated. At the age of 13 years, left subclavian and right cervical carotid arteries were occluded. Right carotid recanalization induced intracranial dissection and death. The child had a Lys350Asp factor B mutation.

CONCLUSION

Arterial steno-occlusive lesions appear as potential complications of dysregulated complement activation in aHUS. Endovascular treatment should be considered cautiously in this setting.

Stroke and cerebrovascular disorders

PURPOSE OF REVIEW

Stroke and cerebrovascular disorders in childhood are a cause for significant morbidity in childhood. There is growing emphasis on understanding the mechanisms of stroke so as to inform developments in investigation and management.

RECENT FINDINGS

Advances have been made in the classification of pediatric stroke, aided by clinical and radiological recognition of patterns of injury and differential outcomes dependent on timing of stroke occurrence. Risk factors are multifactorial, with evidence of geographical and national variation. Causality, however, remains difficult to prove. Recent studies highlight a significant association between stroke recurrence and outcome and the presence of steno-occlusive arterial disease, Moyamoya disease and progressive arteriopathy. Focal arteriopathy of childhood is a new term proposed to refine the nomenclature of childhood arteriopathy. The association between infection and childhood stroke is increasingly recognized, with associations with sinovenous thrombosis and childhood arteriopathy. The recommendation to screen for arteriopathy in genetic conditions such as sickle cell disease is now extended to include children with neurofibromatosis type 1. Perfusion and magnetic resonance wall imaging have helped in the determination of the cause of stroke with impact on management in adults. Two new treatment guidelines have been published (American Heart Association and Chest), but barriers remain to the use of thrombolysis in childhood stroke.

SUMMARY

Continued developments in understanding and practice in childhood stroke are encouraging. However, the absence of clinical trials and evidence-based guidelines is limiting. The conduct of such trials is a goal towards which the International Pediatric Stroke Study is moving.