In most cases, the signs and symptoms of hereditary hypophosphataemia's (hypo-phos-phat-emia) begin in early childhood. The characteristics of the disease vary widely, even among affected members of the same family. Mildly affected individuals may have hypophosphataemia without other signs and symptoms. Severely affected children experience slow growth and are shorter than their peers. They develop bone abnormalities that can interfere with movement and cause bone pain.
The most noticeable of these abnormalities are bowed legs or knock knees (a condition in which the lower legs are positioned at an outward angle). These abnormalities become apparent with weight-bearing activities such as walking. If untreated, they tend to worsen with time.