Uniprot Description A severe bone disease characterized by defective skeletal mineralization and biochemically by deficient activity of the tissue non-specific isoenzyme of alkaline phosphatase. Three more or less distinct types of infantile hypophosphatasia can be identified: (1) type 1 with onset in utero or in early postnatal life, craniostenosis, severe skeletal abnormalities, hypercalcemia, and death in the first year or so of life; (2) type 2 with later, more gradual development of symptoms, moderately severe 'rachitic' skeletal changes and premature loss of teeth; (3) type 3 with no symptoms, the condition being determined on routine studies.