Cerebral Venous Thrombosis with Hyperhomocysteinemia Due to Loss of Heterozygosity at Methylenetetrahydrofolate Reductase (MTHFR) Locus: a Case Report

Loss of heterozygosity (LOH) at methylenetetrahydrofolate reductase (MTHFR) locus has been reported in tumor tissue. But the mutation was never reported in cerebral venous thrombosis (CVT) with hyperhomocysteinemia (HHcy) before. A 14-year-old girl was admitted with an intermittent headache and nausea for 2 months. The plasma homocysteine level was 77.2 µmol/L. Lumbar puncture revealed an intracranial pressure > 330 mmH2O. Cerebral MRI and MRV revealed superior sagittal sinus thrombosis. Whole-exome sequencing revealed LOH at Chr1:11836597–11,867,232 affects exons 10–21 of C1orf167, the entire MTHFR, and exons 1–2 of the CLCN6 gene. The normal allele was the c.665 C > T/677 C > T variant in MTHFR. The patient was treated with nadroparin for 2 weeks, followed by oral rivaroxaban. Supplemental folate and vitamins B12 and B6 were prescribed. One month later, she had no headache and the intracranial pressure had decreased to 215 mmH2O. MRI showed shrinkage of the thrombosis in the superior sagittal sinus, the degree of stenosis had significantly decreased. Rare LOH at the MTHFR locus should be analyzed in CVT with HHcy. With anticoagulation treatment, the prognosis was good.