Below is an instruction that describes a task. Write a response that appropriately completes the request. ### Instruction: PLEASE help me figure out why my legs/feet are cyanotic and can't get oxygen when sitting down. No quality of life and at risk of further permanent damage. Every specialist and hospital is baffled :( Pic inside.'ve posted here before in the past (now deleted), but that was over a year ago. I got a lot of great suggestions and every one of them has now been ruled out.History:30 year old white female, thin, non-drinker, vapes nicotine, no drugs or medsHealth issues prior to this situation: POTS, heart arrhythmias, and EDSA year ago, after my post, I was hospitalized with a vast array of neurological symptoms. To make a long story short, I ended up having a severe B12 deficiency that went unnoticed for 2 years. Low serum B12, extremely high homocysteine and MMA.After getting on the B12 injections, all of my initial symptoms have resolved, except this leg thing which I've never been told is related to the deficiency and idk if it is.Leg Issue:Feet PictureDuration: 15 monthsOnset: Began with some numbness in my toes and transient foot pain when walking, also difficult to walk as if I couldn't feel where my feet were (although sensation was intact). Coloration starts looking funny. A month later, I was sitting at my desk working for about 4 hours and looked down and my feet/calves looked like corpse limbs. Saw a vascular surgeon and had a terrible result on ankle brachial index test. He had me admitted to a major hospital and warned me of risk of double amputation. After release from hospital with no answers, I saw about a million specialists.Symptoms: when in a dependent position (sitting, essentially), it takes about 10 minutes for my feet/calves to start turning colors. They became ice cold to the touch, mottled, dark purple/blue (and sometimes blackish), and there is no detectable pulse in the feet or ankles on doppler or otherwise during this state. The longer I sit, the worse they get. It also has begun to spread higher and higher, if I sit too long it will now go all the way up to my thighs. It is not painful when sitting, they simply feel freezing cold. When I stand up to walk, they are moderately painful (not nerve pain, achey), and walking is clumsy and difficult for a bit. Occasionally, they will become hot, swollen, and bright red but there is no identifiable trigger for this. It happens rarely and isn't related to sitting or elevating them, unsure if this is even related. This cyanosis issue has caused muscle and nerve damage in my feet. Also, lack of toenail growth and yellow thick toenail color.What helps: elevation, when I elevate them, eventually the color will return to normal (pale) and the temperature usually stays cold. Walking also can help the blood flow return to normal. That's it. Soaks in warm water will help the warmth return, but does not solve anything else.What we've ruled out and tests done:Raynaud's syndromeCardiac causesPAD - MRI of both legs showed no atherosclerosis or other signs of PAD. Doctor mentioned "the veins in that area are very narrow but no other findings". He didn't write that on the report and MRI was marked as normal.I had 2 venous doppler exams. Both were done while my legs were elevated and in their good state. Both exams were normal. I expressed again, when elevated they have good blood flow, can they please do the test while my legs are dependent? They said it isn't possible.POTS Blood Pooling - It's not blood pooling, it's a lack of blood flow or a lack of oxygenated bloodBurger's syndromeAll autoimmune conditionsHematologic conditionsDependent acrocyanosis caused by POTSPretty much everything else that I'm sure I'm forgetting hereWorking Diagnoses: PVD of unknown cause, Venous Insufficiency of Legs (Don't know how they got to any of these conclusions but they are also just guesses at Doctor's admission)Other Factors: I do have motor (distal axonal) neuropathy throughout my body, caused by the b12 deficiency, however I have been told this is not related, and the neuropathy is also present in my arms and hands which have no issues in dependent positions.So for one year now under advice of my doctors, I have my feet elevated pretty much at all times. I can not sit on a couch with someone, I can't sit at a desk to work, I can't sit ever. This is affecting all areas of my life, I am babying my feet and legs all day long. I can't do normal things without being able to sit like a normal person.I am out of options, and completely desperate to save my feet. They are already muscle atrophied and partially paralyzed. They are very painful at night when I'm lying in bed (but not usually during the day).Summation: Cyanotic, cold, pulseless feet and calves when sitting. Every time. Will spread up my entire legs if I sit long enough. Clinical damage to muscles and nerves in affected area. MRI and venous doppler are normal. Feet are fine when I'm standing, walking around, or have them elevated. There are NO triggers to this except sitting. (Not triggered by temperature, stress, foods, anything but sitting). There is NOTHING that alleviates this situation except for elevation or walking.I have no idea what is happening but I can not live like this anymore. I have no quality of life. No doctor can give me any answer.I have lost all faith in solving this, but maybe a reddit miracle can happen. You never know. If you read this far, thanks for reading.. ### Response: How was Buerger disease ruled out? Biopsy?This is clearly severe peripheral arterial or venular disease - either medium vessel or small vessel.You ABSOLUTELY should not be using any nicotine products. This is in all likelihood driving the process..