A patient is admitted with 3rd episode of deep venous thrombosis. There is no history of any associated medial illness. All of the following investigations are required for establishing the diagnosis except

It is a cqpillary vascular malformation also called as naevus simplex. Commonly seen in 40% of new borns. It is present at bih,usually involves nape of neck,face,scalp,limbs. With age,it goes for spontaneous regression and disappears completely,usually in one year.