Yours is a complex question and it is hard to do it justie in this forum. Despite the similarities in the name, PAN and microscopic PAN are likely 2 separate diseases. Although both can affect the kidney, other organ systems are different. For instance microsopic PAN an affect the lungs while PAN does not. Microscopic PAN is associated with an antibody blood test called p-ANCA. Since many of the drugs used to treat both of these problems are similar, you are right that it may be more important how severe the kidney problem is and whether it progresses in determining whether or not to move forward with more aggressive therapy such as cylophosphamide.
About Alan Matsumoto, M.D.
Part-time Faculty, Division of Rheumatology
Johns Hopkins University