Based upon this PA ulnar detion view of the wrist, what is the MOST likely diagnosis?

There is focal periostitis at the radial styloid. The radial styloid itself is normal. This is secondary to adjacent inflammation at the extensor pollicis brevis and abductor pollicis longus tendons (De Quervains tenosynovitis). The periosteal reaction of osteomyelitis is usually associated with abnormal underlying bone. The periosteal reaction of hyperophic osteoahropathy is more diffuse involving both the radius and ulna. New bone formation is not a feature of rheumatoid ahritis.