Approximately 10%–20% of families with a clear autosomal dominant pattern of CCMs remain negative for pathogenic variants in CCM1/KRIT1, CCM2, and CCM3/PDCD10, even after comprehensive sequencing and copy‐number variant (CNV) analysis (Flemming et al. 2023; Akers et al. 2025; Scimone et al. 2017). This evidence concerns the gene KRIT1 and cerebrocostomandibular syndrome.