A blue toe can sometimes be benign but sometimes it is a sign of severe disease states. Multiple causes may present as a ‘blue toe’. This article will explain the different causes of blue toes, the way to diagnose them and the different treatments that need to be offered to patients with each type of blue toes.
Blue toes are usually athero-embolic in nature, although a vast differential diagnosis exists (see below). Blue toe lesions are characteristically painful, at least at first. As they are embolic, the lesions of blue toes usually start suddenly. They may evolve over time or not, but embolic lesions tend to be harbingers of more lesions to come. Blue toe syndrome should be differentiated from other conditions in which the toes become blue such as acrocyanosis which is benign and Raynaud’s phenomenon, while the term “blue toe syndrome” should be used to describe emolic, ischemic phenomena.
Causes of blue toe syndrome
There are several mechanisms for blue toe syndrome:
- Mechanical obstruction (secondary to emboli or atherosclerosis) or mechanical damage to blood vessels. By far, embolization is the most common cause of blue toes. The source of the emboli can be in atheromatous plaques or vascular aneurysms.
- Vasospasm – Either due to a primary disease of the blood vessel or secondary to cold, medication or forefoot surgery. Two forms of severe responses to cold include Raynaud’s phenomenon and Pernio. Ergots are migraine medicines that used to be used. Ergots can cause peripheral vasoconstriction. They used to be a common cause of Raynaud’s. If they were given chronically, they could cause a chronic form of blue toe. On angiography the classic picture would be a tapering artery.
- Vasculitis – Vasculitis should always be considered in the differential diagnosis of blue toe syndrome. In vasculitis immune complexes are responsible for the clinical skin manifestations.
- Hyperviscosity – States of hyperviscosity can cause permanent or transient blue toes. Cold agglutinins are a reason for blood hyperviscosity. Another reason is excess white blood cells, elevated platelets and elevated immunoglobulins.
- Hypercoagulability – Hypercoagulable states such as anti-phospholipid syndrome (either on its own or as part of Sytemic Lupus Erythematosus) and essential thrombocytemia have been known to cause blue toes
- Calciphylaxis – In calciphylaxis the cause of blue toes is deposition of calcium. This is rare.
- Medication – Several medications are known to cause blue toes. The most common medicinal cause for blue toes is Warfarin. The mechanism by which Warfarin causes blue toes is probably cholesterol emboli. Steroids have also rarely been described as causes of digital ischemia. A different type of cause is vasospasm secondary to ergot derivatives.
- Toxins – Several toxins and illegal drugs may cause blue toes. These inlcude cocaine and amphetamines.