Bone growth is governed by a number of factors. Initial bone growth is determined by the growth and proliferation of cartilage cells--the cartilage tissue becomes calcified to become bone tissue. Once initial bone growth is complete, the bones undergo constant turnover within the body. Cells called osteoblasts increase bone mass and density by depositing new bone tissue, while cells called osteoclasts decrease bone mass and density by reabsorbing bone. Abnormal growth of any cell type in bone development can lead to bone abnormalities and disease.
Achondroplasia
One bone growth disease is achrondroplasia, a genetic disease that causes abnormal bone growth. Achondroplasia is the most common form of dwarfism, according to the University of Maryland Medical Center. The disease is an autosomal dominant disorders, which means that the child has a 50 percent chance of inherited the disease if one parent has achondroplasia, and a 75 percent chance of achondroplasia if both parents have the disease. Achrondroplasia can also develop as a result of spontaneous genetic mutation during development.
Patients with achondroplasia display stunted bone growth due to a lack of proliferation of cartilage cells-chondrocytes-that act as a precursor to bone. Without chondrocyte proliferation, there is no "blueprint" for bone growth, so the bones do not grow and develop normally. Patients with achondroplasia have skull and spine abnormalities, cranio-facial abnormalities, and short bones in the arms and legs, reports the University of Maryland Medical Center.
Osteogenesis Imperfecta
Another bone growth disorder leads to a disease called osteogenesis imperfecta, also called OI or brittle bone disease. Patients with brittle bone disease display an abnormal breakdown of bone tissue over time due to a defect in bone growth. Normal bone tissue contains bone cells surrounded by a calcified matrix: a substance made up of inorganic minerals that make the bone hard, as well as proteins like collagen that support the structure of the bone and allow for some bone tissue flexibility. Patients with osteogenesis imperfecta do not properly synthesize collagen during bone growth. As a result, the bone matrix lacks collagen, leading to brittle bones, reports MedlinePlus. Due to a lack of collagen, patients with osteogenesis imperfecta are at high risk for bone fracture. Treatment for osteogenesis imperfecta may include exercise, physiotherapy and pain medication to alleviate symptoms of the disease.
Paget's Disease of Bone
Paget's disease of the bone is another bone growth disorder, which is also called osteitis deformans. Patient's with Paget's disease of the bone have excess bone growth, resulting in very large but very weak bones that are prone to fracture. MedlinePlus indicates that Paget's disease can affect one or more bones, but does not generally affect the entire skeleton. Patients with Paget's disease of the bone most commonly experience abnormalities in their pelvis, skull or legs. Treatment for Paget's disease may include surgery or medication to help strengthen the bones.
