Paget disease which is also known as the osteitis deformans is a bone disease that is caused as a result of osteoclast dysfunction. Osteoclasts are one of the major cell types that make up the cellular component of a bone. The cells actually function as the cell type that is responsible for bone resorption. Problems with this group of cells will definitely affect the bone balance between bone resorption and bone remodeling. There are usually two major Paget disease; the monostotic which account for only about 15 percent and polystotic which accounts for the remaining cells.
The occurrence of this pathological condition usually varies from site to site in the body. The disease progression can actually be divided into three main stages which are; 1. Osteolytic stage 2. Mixed osteolytic-osteoblastic stage 3. Osteosclerotic stage The Osteolytic stage is the initial stage that first occurs during the pathological process of the disease. This phase is characterized by significant resorption of the bone as a result of presence of multiple large osteoclasts some of which are made of about 100 nuclei in their cytoplasm.
The second phase which is the mixed osteolytic-osteoblastic phase eventually follows the initial phase and it’s characterized by presence of new disordered set of bone which is predominantly made up of woven bone and some lamellar bone. The deposited bone at this stage are poorly mineralized and therefore soft and porous resulting in a bone with no structural integrity or stability. The effect of this on the bone is that the bone tend to be more liable to fracture whenever there are stressor that are more than what it can withstand or there can be deformation of the soft bone.
The third stage of this pathological process of bone softening is Osteosclerotic stage which is also known as the burn-out phase which marks the hallmark of the pathological processes. It is characterized by bone sclerosis which is compose of lamellar bone with mosaic pattern feature. It also has some coarsely thickened trabeculae and cortices. Normal anatomy and physiology The normal anatomy of bone is that it’s made up of both organic and inorganic component.
The organic component includes the cellular components and the protein matrix while the inorganic component is that of calcium hydroxyapatite which is responsible for the bone strength and hardness and act as the major storage form of substances such as the calcium, phosphorus, sodium and magnesium elements. Bone are usually form by the action of the osteopregnitor cells, osteoblasts, osteoclast and ostocytes. The osteopregnitor cells are the cells types that are responsible for the production of growth factors which governed the bone forming operations.
Osteopregnitor cells later differentiate into osteoblasts which are the cell type responsible for protein synthesis, transportation and arrangement of the protein matrix. They subsequently initiate mineralization in the process. The ostocytes are the bone forming cells and the most abundant of all the bone cells. They are responsible for most of the biological operations that occur in the bone and they actually communicate with one another with their interconnecting network.
They control the calcium and phosphorus balance in the bone and detect mechanical forces which are translated into biological language for proper follow up and responses. The osteoclasts are solely responsible for bone resorption. They ensure there is balance between bone formation and bone destruction. They are actually the macrophages and the monocytes of the bone and act according to the influence of some transcription factors, cytokines and growth factors.
Alteration of normal anatomy and physiology The basic anatomical and physiological alteration that occur in Paget diseases are problems with the anatomical and physiological functions of the affected bone. Anatomical alterations that are involved are in terms of fracture, nerve compressions, and skeletal deformities (such as tibial narrowing and skull enlargement). Pathological fractures are the commonest anatomic alteration and this is usually as a result increase porosity seen in the condition.
It can also result in a situation whereby there will be coarsening of facial bones or cancer of the bone in some patients The main physiological can be attributed to the increase vascularity that can be associated with the polystotic type of Paget disease which tends to predispose the affected individual to an increase level of cardiac output. Increased cardiac output will definitely result in hypertension which also has various physiological consequences on the affected individual.