A 45 year old male had multiple hypoaesthetic mildly erythematous large plaques with elevated margins on trunk and extremities. His ulnar and lateral popliteal nerves on both sides were enlarged. The most probable diagnosis is –
**Core Concept**
Leprosy, also known as Hansen's disease, is a chronic bacterial infection caused by Mycobacterium leprae that primarily affects the skin, peripheral nerves, and mucous membranes. Leprosy is classified into different forms based on the immune response of the patient, ranging from tuberculoid to lepromatous.
**Why the Correct Answer is Right**
The patient's clinical presentation of multiple hypoaesthetic mildly erythematous large plaques with elevated margins on the trunk and extremities, along with enlarged ulnar and lateral popliteal nerves on both sides, is characteristic of borderline lepromatous leprosy. This form of leprosy is characterized by a mixture of skin and nerve involvement, with a relatively high bacterial load and a moderate immune response. The presence of large plaques with elevated margins and nerve enlargement suggests a higher bacterial load and a more intense immune response, which is consistent with borderline lepromatous leprosy.
**Why Each Wrong Option is Incorrect**
**Option A:** Lepromatous leprosy typically presents with widespread skin involvement, including nodules, plaques, and macules, but the nerve involvement is less pronounced compared to borderline lepromatous leprosy.
**Option B:** Borderline tuberculoid leprosy is characterized by a few skin lesions and pronounced nerve involvement, but the lesions are typically smaller and more discrete compared to borderline lepromatous leprosy.
**Option C:** Borderline tuberculoid leprosy has a more pronounced immune response and less bacterial load compared to borderline lepromatous leprosy, which is not consistent with the patient's clinical presentation.
**Clinical Pearl / High-Yield Fact**
In leprosy, the bacterial load and immune response determine the clinical presentation. A high bacterial load and moderate immune response are characteristic of borderline lepromatous leprosy, which presents with large plaques and nerve enlargement. This form of leprosy requires multidrug therapy to control the bacterial load and prevent nerve damage.
**✓ Correct Answer: D. Borderline lepromatous leprosy**