Vitamin D resistant rickets. Familial Hypophosphatemia.
Incidence
Familial hypophosphatemia is inherited as an X-linked trait. Autosomal dominant and recessive forms of familial hypophosphatemia have been reported in the medical literature.
Clinical Characteristics
Vitamin D resistant rickets is defined by its resistance to the vitamin D treatment generally used in deficiency rickets. Typical signs are observed from the first months of life: radiological signs of defective mineralization on cartilage growth plates (rickets) and bones (osteomalacia) and alterations of the phosphocalcic homeostasis in spite of a satisfactory vitamin D status. The clinical phenotype combines bone deformities, mainly at the lower limbs, and other signs depending upon the etiology of the resistance. Two groups of hereditary resistant rickets should be distinguished: hypophosphatemic rickets and pseudo-deficiency rickets. Familial hypophosphatemia is a rare inherited disorder characterized by impaired transport of phosphate and diminished Vitamin-D metabolism in the kidneys. In addition, calcium and phosphate are not absorbed properly in the intestines, which can lead to softening of bones. Familial hypophosphatemia is a form of rickets, a childhood bone disease that results in progressive softening and weakening of the bone structure. In adults, rickets is known as osteomalacia. Major symptoms of familial hypophosphatemia include skeletal malformations, bone pain, abnormally bowed legs, and weakness. Affected infants may experience failure to gain weight and grow at the expected rate (failure to thrive), potentially resulting in short stature. Cases affecting females are usually less severe than those affecting males. Familial hypophosphatemia is inherited as an X-linked trait. Autosomal dominant and recessive forms of familial hypophosphatemia have been reported in the medical literature.
Precipitants
Treatment with vitamin D has been implicated in precipitating spinal cord compression.
Provocation Tests
None
Diagnostic Procedures
Bone X Rays. Hypophosphatemia. High alkaline phosphatase. No hypocalcemia. Reduced renal phosphate Tm.