Systemic diseases are medical conditions that affect multiple organs or systems in the body rather than being localized to a single area. These diseases can disrupt normal bodily functions and may involve the immune system, circulatory system, or other vital systems. Examples include lupus, rheumatoid arthritis, and diabetes. The causes of systemic diseases can vary widely, including genetic factors, environmental influences, and infections. Symptoms often include fatigue, fever, and widespread pain, making diagnosis challenging. Early detection and treatment are crucial for managing these conditions and improving the quality of life for affected individuals.