Familial Cerebral Cavernous Malformation Syndrome with Concomitant Fourth Ventricular Ependymoma: True Association or Mere Coincidence?

Familial cerebral cavernous malformation syndromes are most commonly caused by mutations in one of three genes. The overlap of these genetic malformations with other acquired neoplastic lesions and congenital malformations is still under investigation. To the best of our knowledge, the concurrent occurrence of familial cavernous malformations and ependymoma has not been previously reported in the literature. Herein, we describe a patient with familial cerebral cavernous malformation syndrome and posterior fossa ependymoma. A 17-year-old asymptomatic male was referred to our outpatient neurosurgery clinic after genetic testing identified a familial KRIT1 (CCM1) mutation. The patient's sister had presented with a seizure disorder previously; multiple cavernous malformations were discovered, and a symptomatic large cavernous malformation required a craniotomy for resection. Two years later, she was diagnosed with follicular thyroid cancer due to HRAS (c.182A>G) mutation. The patient and his sister were found to have a novel germline KRIT1 disease-causing variant (c.1739deletion, p.ASN580Ilefs*2) and a variant of uncertain significance, potentially pathogenic (c.1988 A>G, p.Asn663Ser) in cis in CCM1 (KRIT1), of paternal inheritance. Due to the presence of genetic abnormalities, the patient underwent screening imaging of his neuraxis. Multiple cavernous malformations were identified, as was an incidental fourth ventricular mass. Resection of the fourth ventricular lesion was performed, and histopathological examination was consistent with ependymoma. We report a unique case of posterior fossa ependymoma in an individual with a familial cerebral cavernous malformation syndrome and a novel genetic abnormality in KRIT1. The association of these two findings may be valuable in determining a potential genetic association between the two pathologies and elucidating the pathogenesis of both cavernous malformations and ependymomas.