The present invention provides methods, compositions, and kits for the treatment of matrix mineralization disorders such as hypophosphatasia. In particular, the present invention provides polypeptides having a soluble alkaline phosphatase fused to an Fc domain of an immunoglobulin. Such polypeptides can be administered to patients, e.g., subcutaneously, to treat hypophosphatasia using enzyme replacement therapy. The invention also features nucleic acids encoding such polypeptides and the use of the nucleic acids for treating matrix mineralization disorders.
