Disease onset is classically in infancy or childhood and the phenotype is characterized by early onset rickets and short stature, with hypophosphatemia from proximal tubular wasting of phosphate leading to reduced serum PTH, and increased 1,25-Dihydroxyvitamin D (1,25(OH)2D) production in the kidney [18]. The gene discussed is PTH; the disease is hypophosphatemia.