What Causes Numbness And Tingling In Arm?

was sitting at my computer and all the sudden my left hand and fingers went numb and then spread into my hand and up my left arm...a few minutes later I felt part of my left leg going numb and feeling tingly...it went away after about 10 minutes...but to give you some background I have a rare genetic blood disease-I have had several DVT's- where I had blood clots in my left leg from toes to my belly button and I currently have phelibitis in my lower abdomen..but it is a superficial vein that has a clot in it and i have been medically cleared..I have a large varicose vein that goes from my lower abdomen to behind my left knee...Any reason for the numbing sensation...I was kinda freaked out..but my hands and feet have been going numb occasionally but not all at once and I was told they wanted me to get a nerve test at my neurologist but it stopped so I haven't been yet but will this coming week. Any reasons to be worried about the numbing sensation on my left side? No pain though and only lasted 10 minutes or so.