Lepromin test is positive in which leprosy –
**Core Concept**
The lepromin test, also known as the Mitsuda reaction, is a skin test used to assess the immune response to leprosy. It involves injecting a small amount of inactivated Mycobacterium leprae into the skin, and the reaction is measured 7-10 days later. The test is used to differentiate between lepromatous and tuberculoid leprosy.
**Why the Correct Answer is Right**
A positive lepromin test is indicative of a cell-mediated immune response, which is typically seen in tuberculoid leprosy. In this form of leprosy, the immune system is able to mount a strong response against the bacteria, resulting in a positive test. The test is also positive in individuals who have been previously exposed to leprosy and have developed immunity.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because lepromatous leprosy is characterized by a poor cell-mediated immune response, resulting in a negative lepromin test.
* **Option B:** This option is incorrect because borderline leprosy, while having some immune response, does not typically result in a positive lepromin test.
* **Option C:** This option is incorrect because the lepromin test is not typically used to diagnose lepromatous leprosy, and a negative test does not rule out this form of the disease.
**Clinical Pearl / High-Yield Fact**
A positive lepromin test is a good prognostic indicator in leprosy, as it suggests a strong immune response and a better outcome with treatment.
**Correct Answer:** C. Tuberculoid leprosy.