Truncating mutations in the CCM1 gene encoding KRIT1 were recently found in patients affected by inherited cerebral capillary malformations, lesions that cause a wide variety of neurologic problems. However. CCM1 mutations have not been identified in all the families linked to CCM1. Here we demonstrate that the CCMI gene contains right additional exons which may thus encompass the missing mutations. (C) 2001 Elsevier Science B.V. All rights reserved.