Ankylosing spondylitis is a chronic arthritic condition of unknown cause that specifically affects the spine and other joints of the body. It is believed that there is a genetic factor that determines your susceptibility to ankylosing spondylitis (AS). 90% people with AS have an abnormal antigen the HLA-B27. There is no definitive treatment for AS. The most important part is an exercise programme to maintain good posture and functional range of movement of the joints. The spine gradually gets stiffer and stiffer to the extent that they have what is known as bamboo spine over a period of time. Other treatment is only symptomatic depending on patient tolerance. The patient could be on drugs to reduce inflammation (the active process that damages joints). Doctors normally juggle with either single or a combination of these. There are reports that a drug called Sulphasalazine helps modify the disease. There are some other drugs also which modify the immune response that have been tried. However, as of today there is no definite cure. Disease may burn out after sometime, in some patients, but there is no way of predicting the outcome. When the joint gets damaged significantly, the joints may get fused with no movement. In joints like hip and knee, artificial joints can be implanted to improve function.
Regarding your son, CTEV is a difficult problem to treat. However, if after treatment there is a residual deformity then this must be addressed. The longer you delay lesser the chances of correction of the foot deformity. Though correction can be improved even in a later age group this is at a compromise of foot suppleness. I would suggest you take him to an orthopaedic surgeon who deals in such problems. There are newer techniques that are available and also one old technique (Ponsetis method) has become popular with good results. Do discuss the matter with you doctor so that he can advise you better.