The evaluation of efficacy is performed by laboratory monitoring of bone density and resorption markers and clinical monitoring of bone density improvement. This is a prospective, randomized, parallel group, single blind study of one year treatment with zoledronic acid every 6 months as compared to one year treatment with zoledronic acid every 3 months and to placebo every 3 months in patients with hemoglobin syndromes and risk of skeletal complications.

Inclusion Criteria:

• Patients with thalassaemia or sickle cell anaemia and bone density, z-scores < -1.5, in at least one of the examined sites
• Normal renal function. Urea and creatinine should not exceed > 2-fold the upper limit of normal (< 2 x ULN).

Exclusion Criteria:

-

Other protocol-defined inclusion / exclusion criteria may apply.