### Date : 2024-12-02 15:16 ### Topic : Pathergy Test #rheumatology ---- ### **Pathergy Test** The **pathergy test** is a diagnostic test used to assess **hypersensitivity** to minor skin trauma, which is typically associated with **Behçet's disease**. It involves the **induction of a small skin lesion** following a **prick or needle insertion** into the skin. A positive test is characterized by the development of a **raised red bump or pustule** at the site of the skin injury within **24 to 48 hours**. --- ### **Role in Behçet's Disease** The **pathergy test** is most commonly used in the diagnosis of **Behçet's disease**, a **multisystem inflammatory disorder** characterized by recurrent **oral ulcers**, **genital ulcers**, **eye inflammation (uveitis)**, and **skin lesions**. 1. **Pathergy Phenomenon in Behçet's Disease**: - **Pathergy** refers to the exaggerated skin reaction to minor trauma. - A **positive pathergy test** is highly suggestive of **Behçet’s disease**, particularly when combined with clinical features like **oral and genital ulcers**. - It occurs in up to **30-60% of patients** with **Behçet’s disease**, although its presence is not required for diagnosis. 2. **Other Causes**: - While the **pathergy phenomenon** is most strongly associated with **Behçet's disease**, it may also be seen in **other inflammatory conditions**, such as **tuberculosis**, **leprosy**, and **pyoderma gangrenosum**, but it is less specific. --- ### **How the Pathergy Test is Performed** 1. **Procedure**: - A sterile needle or small device is used to make a slight **prick** or **insertion** in the skin, usually on the forearm. - The test site is typically observed over a period of **24 to 48 hours**. 2. **Interpretation**: - **Positive Pathergy Test**: The development of a **pustule** or **red bump** at the site of the prick. This indicates **skin hypersensitivity**, which is associated with **Behçet's disease**. - **Negative Pathergy Test**: No reaction at the test site. This is more typical in healthy individuals or patients with other conditions not related to **Behçet’s disease**. --- ### **Clinical Use of Pathergy Test** - **Diagnostic Aid**: The pathergy test can support the diagnosis of **Behçet’s disease**, especially in individuals with suggestive clinical symptoms (e.g., oral and genital ulcers, eye inflammation). - **Not Diagnostic by Itself**: A positive pathergy test alone is not diagnostic of Behçet's disease, as it can occur in other conditions as well. The test should be interpreted alongside other clinical findings and diagnostic tests. --- ### **Limitations of the Pathergy Test** - **Geographic and Racial Variability**: The pathergy phenomenon is more commonly seen in patients from **Middle Eastern**, **Eastern Mediterranean**, and **Asian** populations, but it is less common in **Caucasians** or individuals from **Western countries**. - **Not Universally Present**: Not all patients with **Behçet's disease** will have a positive pathergy test, so a negative result does not rule out the disease. - **False Positives**: The pathergy test can sometimes be positive in **healthy individuals** or in patients with **other inflammatory diseases**. --- ### **Summary** The **pathergy test** is a diagnostic tool used primarily in the diagnosis of **Behçet's disease**, characterized by a skin reaction (such as a pustule or red bump) at the site of minor trauma. It helps in identifying hypersensitivity to skin injury, which is a hallmark of the disease. While a **positive pathergy test** is suggestive of **Behçet’s disease**, it is not diagnostic on its own and should be used in conjunction with other clinical findings and tests. ### Reference: - ### Connected Documents: -