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Recurrent dural venous sinus thrombosis in a 20‐year‐old man: nature or nurture?

A 20-year-old man presented with sudden onset occipital headache, confusion and vomiting. Computed tomography (CT) revealed a recent thrombus in the superior sagittal and right straight sinus, consistent with a dural sinus thrombosis (left). Haemoglobin concentration (Hb) on admission was 147 g/l and mean cell volume (MCV) 105 fl (not further investigated). There was no personal or family history of venous thrombosis and a thrombophilia screen after 6 months anti-coagulation with warfarin was planned. Three weeks after cessation of anti-coagulation the patient represented with identical symptoms. Repeat CT venography demonstrated a filling defect within the right internal jugular vein, right transverse sinus and sigmoid sinus. There was almost complete occlusion of the straight sinus and transverse sinuses in keeping with an acute event, although partial re-canalisation of the previous extensive sagittal sinus thrombus was seen (right). Intravenous heparin was given followed by warfarin and the patient was referred to haematology. Full blood count on admission showed Hb 108 g/l and MCV 125 fl with a blood film confirming macrocytosis and showing hypersegmented neutrophils. Serum vitamin B12 was undetectable (<60 ng/l) with normal ferritin and folate levels. A working diagnosis was made of thrombosis secondary to hyperhomocysteinaemia, which was supported by a markedly elevated plasma homocysteine level of 202 lmol/l (0 – 14Æ3 lmol/l) on admission. Vitamin B12 replacement was commenced (1 mg hydroxocobalamin intramuscularly thrice weekly for 2 weeks) and following this the homocysteine level quickly returned to normal (11Æ7 lmol/l.) The patient was also commenced on folate supplements, despite normal plasma levels. On further questioning it was noted that since weaning at the age of 18 months, the patient’s diet had been limited to white bread, crisps, fizzy drinks and blackcurrant squash, consistent with a diagnosis of dietary B12 deficiency (autoantibody screen was negative). Regarding other risk factors for thrombosis he was found to be heterozygous for both the F5 R506Q (factor V Leiden) mutation and the substitution of cytosine by thymine at position 677 of the gene encoding methylenetetrahydrofolatereductase (MTHFR). Patients homozygous for the latter mutation can experience up to a 50% reduction in the activity of MTHFR, which can be associated with hyperhomocysteinaemia in those who are deficient in folic acid or vitamin B12. In this case there was no laboratory evidence of anti-phospholipid syndrome and the rest of the thrombophilia screen was normal. High levels of plasma homocysteine are known to be a risk factor for thrombosis; particularly for thrombi in an unusual site, with up to a fourfold increased risk of cerebral vein thrombosis having been reported. In terms of future management of this young man with recurrent, potentially fatal thromboses the question of life long anti-coagulation must be addressed given that he has both reversible and inherited risk factors.