Windguy, I don't think you should assume that it is not service related. Yes there is a gene associated with AS (HLA B27) but not everyone with this gene develops AS just like not everyone with the BRCA gene develops breast or ovarian cancer. In the case of AS it appears that it takes a triggering event to activate the disease. The gene just makes you more susceptible to it. It also appears likely that any kind of overload on your system can be that triggering event (stress, injury, bacterial infection). If you were at war, it is likely you had all of these. And that's not even addressing the amount of equipment you carried around daily which stressed already vulnerable joints. I would encourage veterans to file a claim and fight for your rating. You deserve it.