What Causes Granuloma Annulare?

I have been diagnosed with granuloma annulare by a dermatologist, and may soon be put on accutane at age 72, but another doctor has determined that my calcium level is too high at 10.9, and Vit. D is too low.Could one be causing the other? I'm hoping to avoid this rash getting even more wide spread, now on 50 percent of my torso.