A Novel CCM2 Gene Mutation Associated With Cerebral Cavernous Malformation

Cavernous malformations are congenital abnormalities of the cerebral vessels that affect 0.5% to 0.7% of the population. They occur in two forms: a sporadic form characterized by isolated lesions, and a familial form characterized by multiple lesions with an autosomal dominant mode of inheritance. The management of patients with cavernous malformations, particularly those with the familial form of the disease, remains a challenge because little is known regarding the natural history. The authors report the results of an ongoing study in which six families afflicted by familial cavernous malformations have been prospectively followed with serial interviews, physical examinations, and magnetic resonance (MR) imaging at 6- to 12-month intervals. A total of 59 members of these six families were screened for protocol enrollment; 31 (53%) had MR evidence of familial cavernous malformations. Nineteen (61%) of these 31 patients were symptomatic, with seizures in 12 (39%), recurrent headaches in 16 (52%), focal sensory/motor deficits in three (10%), and visual field deficits in two (6%). Twenty-one of these 31 patients underwent at least two serial clinical and MR imaging examinations. A total of 128 individual cavernous malformations (mean 6.5 +/- 3.8 lesions/patient) were identified and followed radiographically. During a mean follow-up period of 2.2 years (range 1 to 5.5 years), serial MR images demonstrated 17 new lesions in six (29%) of the 21 patients; 13 lesions (10%) showed changes in signal characteristics, and five lesions (3.9%) changed significantly in size. The incidence of symptomatic hemorrhage was 1.1% per lesion per year. The results of this study demonstrate that the familial form of cavernous malformations is a dynamic disease; serial MR images revealed changes in the number, size, and imaging characteristics of lesions consistent with acute or resolving hemorrhage. It is believed that the de novo development of new lesions in this disease has not been previously reported. These findings suggest that patients with familial cavernous malformations require careful follow-up monitoring, and that significant changes in neurological symptoms warrant repeat MR imaging. Surgery should be considered only for lesions that produce repetitive or progressive symptoms. Prophylactic resection of asymptomatic lesions does not appear to be indicated.

Cerebral cavernous malformations (CCMs) are congenital vascular anomalies of the central nervous system that can result in hemorrhagic stroke, seizures, recurrent headaches, and focal neurologic deficits. Mutations in the gene KRIT1 are responsible for type 1 CCM (CCM1). We report that a novel gene, MGC4607, exhibits eight different mutations in nine families with type 2 CCM (CCM2). MGC4607, similar to the KRIT1 binding partner ICAP1alpha, encodes a protein with a phosphotyrosine-binding domain. This protein may be part of the complex pathway of integrin signaling that, when perturbed, causes abnormal vascular morphogenesis in the brain, leading to CCM formation.

Cerebral cavernous malformations (CCM) are vascular malformations that can occur as a sporadic or a familial autosomal dominant disorder. Clinical and cerebral MRI data on large series of patients with a genetic form of the disease are now available. In addition, three CCM genes have been identified: CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10. These recent developments in clinical and molecular genetics have given us useful information about clinical care and genetic counselling and have broadened our understanding of the mechanisms of this disorder.