relapse
Meaning of relapse: Whether something has come back or merely resurfaced depends on whether it ever truly left, which the word alone does not settle.
Definition of relapse
Relapse is the return of a disease, or of its signs and symptoms, after a period of improvement or apparent control. The word spans cancer care, infection, autoimmune disease, psychiatry and addiction medicine, and what it implies shifts with the setting: sometimes a disease has come back, sometimes a quiet one has flared.
What does it mean in different settings?
| Setting | What relapse describes |
|---|---|
| Cancer | Disease detectable again after a period with no evidence of it; the word recurrence is often preferred |
| Autoimmune and inflammatory disease | A flare of activity after a quiet stretch, in a condition that never went away |
| Infection | The original organism becoming active again, as opposed to reinfection with a new one |
| Mental health conditions | Return of symptoms after a period of recovery |
| Substance use disorder | Return to use after a period of abstinence, now described as a feature of a chronic condition rather than a failure |
How is a relapse told apart from something new?
By evidence that it is the same process rather than a separate one. In cancer, tissue from the new site is compared against the original tumor under the microscope and by its molecular features; a genuinely new cancer looks different and behaves differently. In infection, genetic comparison of the organism separates relapse from reinfection, and the distinction matters because relapse suggests the first course of treatment did not clear the organism while reinfection suggests renewed exposure. The vocabulary also varies: biochemical relapse describes a rise in a blood marker before anything can be seen on a scan, which is a relapse by measurement rather than by symptom.
Why is monitoring continued after symptoms disappear?
Because remission is not the same as cure. Remission means no detectable disease, and detection has limits; small amounts can persist below what any test will show. A relapse can therefore follow a long quiet interval, and it is generally easier to act on when it is small and confined. Conditions with a known pattern of relapse are followed on a schedule after treatment finishes, with the interval and the method chosen to match where and how that particular disease tends to reappear. Once several years pass without any sign of return, the schedule usually loosens.
Used in a sentence
Follow-up imaging was ordered after the patient reported symptoms concerning for relapse.
Good to know
A relapse is separated from a new, unrelated occurrence of disease by evidence that it represents the same underlying condition returning rather than a separate process.
Word origin
Where “relapse” comes from
From Latin relabi, meaning to slip back, formed from re-, meaning again, and labi, meaning to slip or slide.