De novo intracranial arteriovenous malformation development after endovascular treatment for a pial arteriovenous fistula in capillary malformation-arteriovenous malformation syndrome.

Capillary malformation-arteriovenous malformation (CM-AVM) syndrome is a newly described entity characterized by autosomal dominantly inherited multifocal capillary malformations caused by RASA1 mutations (CM-AVM1) or EPHB4 mutations (CM-AVM2). Concurrent high-flow vascular anomalies in the brain are often present in the form of intracranial AVM or arteriovenous fistula (AVF). These high-flow lesions are often identified at or soon after birth because of the characteristic unique capillary malformations or a systemic disorder due to a high-flow shunt, such as respiratory distress or heart failure. However, de novo intracranial AVMs have not been reported in patients with CM-AVM syndrome. Herein, we report the case of a six-year-old boy with CM-AVM1 who had been treated for an intracranial pial arteriovenous fistula approximately five years previously, in whom a de novo intracranial AVM was identified on a follow-up angiographic study. To the best of our knowledge, this report is the first to document a de novo intracranial AVM in a patient with CM-AVM. We recommend careful neuroimaging follow-up even if initial neuroimaging screening is negative because of the risk of de novo AVM development.