Many systemic diseases are reflected in the oral mucosa, maxilla, and mandible. Mucosal changes may include ulceration or mucosal bleeding. Immunodeficiency can lead to opportunistic diseases such as infection¡ and neoplasia. Bone disease can affect the maxilla and mandible. Systemic disease can cause dental and periodontal changes¡ Drugs prescribed for a systemic disease can affect oral tissue. Oral conditions have an impact on overall health and disease. Bacteria from the mouth can cause infection in other parts of the body when the immune system has been compromised by disease or medical treatments (e.g., infective endocarditis). Systemic conditions and their treatment are also known to impact on oral health (e.g., reduced saliva flow, altered balance of oral microorganisms). Oral manifestations - Commonly occurs in mucosal surface of buccal mucosa , vestibules, tongue,lips, floor of the mouth, palate. Appears weeks or months before the skin¡ lesions. Lesions are bilaterally symmetrical. Oral health is essential to general health and well-being at every stage of life. A healthy mouth enables not only nutrition of the physical body, but also enhances social interaction and promotes self-esteem and feelings of well-being. The mouth serves as a “window” to the rest of the body, providing signals of general health disorders. For example, mouth lesions may be the first signs of HIV infection, aphthous ulcers are occasionally a manifestation of Coeliac disease or Crohn’s disease, pale and bleeding gums can be a marker for blood disorders, bone loss in the lower jaw can be an early indicator of skeletal osteoporosis, and changes in tooth appearance can indicate bulimia or anorexia. The presence of many compounds (e.g., alcohol, nicotine, opiates, drugs, hormones, environmental toxins, antibodies) in the body can also be detected in the saliva. Oral disease is the most widespread chronic disease, despite being highly preventable.