All of the following are cardinal signs of acute inflammation EXCEPT:

Explanation

## Cardinal Signs of Acute Inflammation **Key Point:** The five cardinal signs of acute inflammation were first described by Celsus and later expanded by Virchow. Only four are universally recognized as cardinal signs; suppuration is a *consequence* of acute inflammation, not a cardinal sign itself. ### The True Cardinal Signs | Sign | Latin | Mechanism | Pathophysiology | |------|-------|-----------|------------------| | Redness | Rubor | Vasodilation of arterioles | Increased blood flow (RBCs) | | Heat | Calor | Increased blood flow | Increased metabolic activity | | Swelling | Tumor | Exudation of fluid | Increased vascular permeability | | Pain | Dolor | Stimulation of nerve endings | Bradykinin, prostaglandins, substance P | | Loss of function | Functio laesa | Tissue damage + pain | Reflex inhibition and structural damage | **High-Yield:** Suppuration (pus formation) occurs *as a result* of acute inflammation when neutrophils accumulate and die, releasing their contents. It is a **secondary phenomenon**, not a cardinal sign. Suppuration indicates progression to abscess formation, which is a *complication* of acute inflammation, not a defining feature. ### Why Suppuration Is Not a Cardinal Sign 1. **Not always present** — Many acute inflammatory responses resolve without pus formation (e.g., acute viral pharyngitis, acute gastroenteritis). 2. **Occurs late** — Suppuration develops only after significant neutrophil infiltration and death. 3. **Indicates tissue necrosis** — Pus formation means tissue has been destroyed; it is an endpoint, not a cardinal feature. **Clinical Pearl:** A sterile acute inflammatory response (e.g., acute myocardial infarction, acute pancreatitis) shows all four cardinal signs but no suppuration. Conversely, some chronic infections (e.g., tuberculosis) may show suppuration without prominent rubor or calor. **Mnemonic:** **RSVP** for the four true cardinal signs — **R**ubor, **S**welling (tumor), **V**alor (dolor/pain), **P**erfunctio (loss of function). Suppuration is the **S**equela, not a sign.