Case report: 2.5-year-old male child admitted with complaints of multiple episodes of vomiting, drowsy, reduced interaction with parents. Clinical examination showed reduced movement of the right lower limb. Right lower limb appeared hypotonic and flaccid. CSF examinations showed turbid fluid, Wbc -1490 cells/microliter 85% neutrophil, 10% lymphocyte. CSF culture – no growth. Encephalitis screen - negative MRI (BRAIN) showed Non enhancing T2 FLAIR hyperintense and T1 hypointense region involving the left thalamus and basal ganglia and internal capsule mildly compressing 3rd ventricle with asymmetric dilatation of left lateral ventricle and midline shift to right compressing the body of right lateral ventricle. Hemorrhagic changes in the affected left deep grey matter nuclei, suggestive of acute necrotizing encephalitis or deep cerebral vein thrombosis. Real time PCR revealed heterozygous mutation of factor V leiden.

Diagnosis: Cerebral venous thrombosis associated with heterozygous factor V leiden mutation.

Treatment: Low molecular weight heparin, oral anticoagulants.

Conclusion: Factor V mutation is a common inherited risk factor for venous thrombosis in children. Due to the rapid and fatal consequences of this cerebrovascular event, prompt response with an antithrombotic must be administered to prevent any further complications. Further studies are essential to determine the most appropriate lifelong anticoagulation, its posology and duration in the pediatric population.