Dental characteristics of hypophosphatemic rickets. Case report

Hypophosphatemic rickets (HR), also known as refractory, vitamin D resistant rickets, is a hereditary disease linked to the X chromosome. It is characterized by the metabolic disturbance of calcium and phosphate, which causes defective calcifi cation of mineralized structures such as bones and teeth.1,2 It is the most common type of rickets found in developed countries. Its incidence can be counted at 1 in 20,000 individuals. It was fi rst described in 1937 by Albright et al who reported that patients affl icted by this disease did not respond to usual vitamin-D treatment. Vitamin D is essential for the mineralization of bone matrix synthesized by osteoblasts.3 Pathophysiology of the disease consists on a decrease of phosphate resorption at the level of the kidney’s proximal tubule. This elicits phosphate loss through urine, and therefore, persistent hypophosphatemia joined by anomalies in the calcium and phosphate intestinal resorption. Low phosphate levels in the blood cause bone mineralization defects with rickets signs and symptoms, which are frequently evident when patients reach about 18 months of age.4-6 This is a hereditary disease, with dominant transmission linked to sex chromosome X, therefore, affected males transmit the disease-responsible gene, located at the distal section of the short arm of the X chromosome (Xp22.1-p22.2) to all his female offspring and to none of the male ones, while an affected female transmits the gene to half her male offspring and half her female offspring, therefore, all her offspring, regardless of gender will have 50% probability of receiving the hypophosphatemic rickets gene.1,7,8 In 1995 HR gene was finally cloned, and the product of this gene, called PHEX gene (phosphate Dental characteristics of hypophosphatemic rickets. Case report