Increased tartrate-resistant acid phosphatase serum levels in ankylosing spondylitis and relationship with the inflammatory process

Osteoporosis is a well described feature of ankylosing spondylitis (AS) with vertebral compression fractures and low bone mineral density, mainly at the femoral neck.1–3 Bone remodelling has been previously evaluated in AS: bone resorption markers (crosslinked telopeptide of collagen type I, βCTX-I) were found to be increased in some studies,4 5 but not all,3 while divergent results were obtained for bone formation markers (normal or decreased osteocalcin levels, normal or elevated bone alkaline phosphatase (BAP)).1 Bone metabolism may also be evaluated by means of a new marker, namely isoform 5b of tartrate-resistant acid phosphatase (TRACP5b) which is a specific …