Biochemical Response to Bisphosphonate Therapy in Pagetic Patients with Skull Involvement

The aims of this study were to compare the response to therapy in disease activity in pagetic patients with and without skull involvement and the usefulness of bone markers in the evaluation of these patients. Forty patients with Paget’s disease treated with tiludronate and 26 healthy controls were included. Serum total and bone alkaline phosphatases (TAP, BAP), procollagen I N propeptide (PINP), and urinary N- and C-terminal cross-linking telopeptides of collagen I (NTX, α-α CTX, and β-β CTX) were measured at baseline and 6 months after therapy. The extent of the disease was evaluated using the Coutris’ index. Pagetic patients were classified into three groups: patients with skull involvement (G-I, n = 12), patients without skull involvement (G-II, n = 28), and a subgroup of patients from G-II without skull involvement but with similar disease extent to G-I (G-III, n = 10). At baseline, patients from G-I showed significantly higher values in most markers compared to G-II. α-α CTX was the marker with the highest values in all groups. Moreover, monostotic patients with skull involvement showed higher serum baseline values of TAP per unit of affected area than monostotic patients without skull involvement. After therapy, the percentage of patients with markers within the normal range was lower in G-I than in G-II and G-III. In conclusion, pagetic patients with skull involvement showed a marked increase in bone turnover and a lower response to therapy.