Cocaine is available in 2 forms- the salt-cocaine hydrochloride, and the "free base", prepared by heating the salt with baking soda.
The salt can be snorted or injected but cannot be smoked as it disintegrates, while the freebase is smoked. As the freebase is available as white lumps, it is often referred to as "rock".
When smoked, freebase or rock gives a "high" within 5 minutes. It takes longer for the "high" to appear when snorted (inhaled) through the nose- around 20 minutes.
The man I saw had been snorting cocaine for many years. This is the background against which cocaine induced midline destructive lesion (CIMDL) occurs. Typically, it involves perforation of the septum, but can be more extensive, involve the lateral walls or even the soft or hard palate.
Such people do not have systemic vasculitis. They have localised destruction of the septum. Systemic symptoms are absent apart from fatigue, which is very common in cocaine users.
These people would typically test positive for pANCA on immunofluorescence, but not for MPO on ELISA. Here, the pANCA is directed not towards MPO, but an antigen called human neutrophil elastase or HNE, considered quite specific for CIMDL.
However, 50% also test positive for c-ANCA and PR3. This causes diagnostic confusion with GPA (Wegener's), which is of course, usually associated with cANCA & PR3 and can cause nasal perforation as well. Unlike CIMDL however, GPA would not show positive pANCA on immunofluorescence. CIMDL patients also tend to have more extensive septal destruction.
A totally different phenotype of cocaine is a genuine vasculitis associated with gangrenous skin lesions and joint pains, alongside systemic symptoms such as fever, night sweats, weight loss, myalgia. A positive urinalysis or proteinuria and lung lesions (the characteristic features of GPA) are only found in a minority of cases.
The skin lesions are striking- often takes the form of retiform purpura.
Cocaine abusers with this particular phenotype often have a bizarre double positive on ANCA testing. All of them test positive for MPO ANCA, and around 50% test positive for PR3 ANCA.
It is this latter group, with the genuine vasculitis, that has been associated with levamisole.
Levamisole is an antihelminth used in veterinary practice, and is used to "cut" (bulk up) cocaine in 70% of such cases. Levamisole has some amphetamine like properties itself and hence ideally suited for abuse.
Cocaine induced vasculitis can be differentiated from GPA through the double positive ANCA, and the bizarre skin lesions. A proportion of such patients are leucopenic, which is rare in GPA. However, just like GPA, cocaine induced vasculitis requires immunosuppression.
