We reported a family with early onset cerebrovascular disease. Patient 1 (a 36-year-old man) demonstrated a combination of livedo reticularis and cerebral infarction as previously described as Sneddon syndrome. He also showed transient focal neurologic symptoms and mild dementia. Patient 2 (an elder sister of Patient 1) was suffering from migraine. Their father and paternal uncle died of cerebral infarction, which had developed in their thirties or forties. Patients 1 and 2 showed MRI findings compatible with encephalopathy with Binswanger-type. Contrary to the previous reports on Binswanger-type encephalopathy, both of these patients demonstrated decreased levels of fibrinogen as well as those of factor V, together with negative antiphospholipid antibody. Thus, juvenile onset, autosomal dominant inheritance, the diversity of clinical findings and the coagulopathy in this family were characteristic features. The level of thrombin-antithrombin III complex (TAT) was markedly increased in Patient 1. Treatment with antithrombin (argatroban 20mg i.v. everyday for 28 days) not only reduced the level of TAT but also improved the livedo reticularis and neurological findings. Although gene analysis has not been performed yet on this family, this condition is similar to cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL), which involve juvenile cerebral infarction and dementia as well as migraine.