What term describes a condition that develops as a complication of an existing disease or injury?

The term that describes a condition that develops as a complication of an existing disease or injury is "sequel." This term is used in medical contexts to refer to a consequence or an aftereffect that arises from a prior condition or injury. For instance, after a person has suffered a stroke, they may experience physical limitations or cognitive challenges; these issues can be termed sequels of the initial stroke.

In contrast, "symptom" refers to a physical or mental feature that indicates a condition or disease but is not a complication that arises from it. "Syndrome" describes a collection of symptoms or signs that occur together and characterize a particular abnormality or condition, rather than indicating the progression or complication of a disease. "Diagnosis" pertains to the identification of a disease or condition based on signs and symptoms, rather than describing a subsequent complication.

Understanding these terms helps to clarify the relationship between an initial medical issue and any subsequent complications that may arise, illustrating the nuanced terminology used in the healthcare field.