The frameshift Leu220Phefs*2 variant in KRIT1 accounts for early acute bleeding in patients affected by cerebral cavernous malformation

Background and Objectives: Cerebral cavernous malformation (CCM) is a neurovascular disease characterized by abnormally expanded and tortuous microvessels with increased predisposition to thrombosis and focal hemorrhage. Its incidence is estimated to range between 0.4% and 0.8%. Sporadic and familial forms of CCM are described. The first one is characterized by single lesion, while the familial form is defined by multiple malformations. In this scenario, more than 300 mutations affecting the CCM genes have been described to date, but the exact pathogenic mechanism is yet unknown. Most of the causative variants of KRIT1 gene are frameshift but there are many missense and nonsense variants and they have been found some splicing mutations. The diagnosis is based on magnetic resonance images (MRI) and genetic testing. Case report: A 15-year-old male presented with a two weeks duration worsening headache accompanied by vomiting and three months behavioral changes. Computer tomography revealed a large right temporal lesion with other smaller in left parietal and left cerebellar region. At the time of diagnosis, the two siblings of the proband were asymptomatic. Nevertheless, four months later, the 7-years-old brother was admitted to the emergency room for balance deficit, diplopia, right-hitting nystagmus and stiff neck with deviation of the head. A cerebral CT revealed polylobate hyperdense mass of the middle cerebral pedicle associated to acute bleeding. A genetic testing for hereditary cavernous brain malformation was carried out. Results: The molecular analysis identified a 2-bp duplication (NM_194456.1:c.658_659dupTT) as heterozygous within the exon 8 of CCM1/KRIT1 gene (Fig. 1C). This duplication leads to a frameshift variant, resulting in a premature stop codon (p.Leu220Phefs*2). Discussion: The clinical data collected confirm the variable phenotypic expression of CCM and suggest a greater severity of symptoms in the youngest patients.