[Hypophosphatemia of a genetic origin]

Familial hypophosphatemia are either primitive disorders of renal phosphate handling, isolated as in X linked hypophosphatemic rickets (XLHR) or associated with alterations of renal handling of other solutes. They can also occur in the course of a number of other inherited diseases such as vitamin D dependent rickets type I or II and distal tubular acidosis. The molecular basis of most of these diseases are unknown. Chronic hypophosphatemia induces an alteration of bone mineralisation with rickets in children and osteomalacia in children and adults. Hypophosphatemia and the bone disease are most important in XLHR or VDDR. Treatment with oral phosphate and 1 alpha hydroxylated vitamin D metabolites, and in some cases calcium, tends to correct the hypophosphatemia and the bone disease. Treatment of the associated metabolic disorder in certain Fanconi syndromes can correct hypophosphatemia. In the forms associated with hypocalcemia, phosphate therapy is not indicated, but rather calcium therapy.