According to the Ridley-Jopling classification, which type of leprosy is characterized by few lesions, well-defined borders, and high cell-mediated immunity with low bacillary load?

Explanation

## Ridley-Jopling Classification Overview The Ridley-Jopling classification divides leprosy into five immunological types based on clinical, histopathological, and bacteriological features. ### Tuberculoid Leprosy (TT) **Key Point:** Tuberculoid leprosy represents the **most resistant** end of the immunological spectrum, with strong cell-mediated immunity (CMI) and minimal bacillary load. | Feature | Tuberculoid Leprosy | | --- | --- | | **Number of lesions** | Few (1–5) | | **Lesion borders** | Well-defined, sharp | | **Sensory loss** | Early and marked | | **Bacillary index (BI)** | 0–1 (paucibacillary) | | **CMI response** | Strong (positive lepromin test) | | **Nerve involvement** | Early, asymmetric, marked | | **Histology** | Epithelioid granulomas, few bacilli | **High-Yield:** Tuberculoid leprosy is the **most benign** form with excellent prognosis but rapid nerve damage if untreated. It is **paucibacillary** (low infectivity). ### Comparison with Other Types | Type | Lesions | BI | CMI | Infectivity | | --- | --- | --- | --- | --- | | **TT (Tuberculoid)** | Few, well-defined | 0–1 | Strong | Low | | **BT (Borderline TB)** | Moderate, asymmetric | 2–4 | Moderate-strong | Low | | **BB (Mid-borderline)** | Many, variable | 4–5 | Moderate | Moderate | | **BL (Borderline L)** | Many, ill-defined | 5–6 | Weak | High | | **LL (Lepromatous)** | Numerous, ill-defined | 6 | Absent | Very high | **Clinical Pearl:** Tuberculoid leprosy patients often present with **asymmetric nerve thickening and early sensory loss** in lesions, making early diagnosis and treatment crucial to prevent permanent disability. **Mnemonic:** **T**uberculoid = **T**ight (few lesions), **T**hick nerves (early involvement), **T**ough immunity (strong CMI).