Vitamin D Receptor Gene Polymorphism in Patients with Osteomalacic Myopathy in Egypt

Abstract

Vitamin D complex, a group of lipid soluble compounds, has been shown to play central role in various biological processes in bone biology, autoimmune diseases, cell growth, inflammation, neuromuscular and other immune functions. It can be provided from many food products or endogenously produced by ultraviolet rays from sunlight when the skin is exposed to initiate vitamin D synthesis. Vitamin D exerts its biological functions via binding to vitamin D receptor (VDR) which belongs to the steroid hormone receptor family. The VDR gene is distributed on chromosome 12q12-q14. In addition to its indirect classic effects on intestine, parathyroid glands, bone and kidneys that acts on calcium and phosphate homeostasis in muscle fibers. Vitamin D acts directly on muscle cells via VDR that causes either rapid effects also on intracellular calcium and phosphate homeostasis and transport or on muscle differentiation, contractile proteins expression/activity and phospholipid activity and thereby affects muscle form, function and metabolism. The muscle involvement in hypovitaminosis D was broadly named Osteomalacic myopathy and is characterized by muscular weakness mainly proximal group of muscles together with musculoskeletal pain, symptoms could be markedly disabling