According to the text, a complex medical condition involves the involvement of multiple body systems and can be challenging to manage. Compared to simpler conditions that may only affect one part of the body, complex conditions such as Alzheimer's disease, cancer, HIV/AIDS, and chronic illnesses like kidney disease, heart failure, diabetes, and high blood pressure require special consideration and treatment. These conditions may have complex genetic causes and risk factors, long latency periods, and can affect individuals with mental and physical disabilities, including those with intellectual disabilities and chronic illnesses like depression, blindness, and mobility disorders. Some common examples of complex genetic diseases include heart disease, diabetes, and cancer. Overall, these complex medical conditions can have a significant impact on a person's life and require specialized care and treatment.