Classification of Leprosy: WHO and Ridley-Jopling Types Explained

Yes, directly. The WHO's paucibacillary (PB) vs multibacillary (MB) split decides the multidrug therapy (MDT) regimen and duration. Paucibacillary, five or fewer skin lesions, no bacilli seen on skin smear, is treated with rifampicin and dapsone for 6 months. Multibacillary, more than five lesions or bacilli present on smear, is treated with rifampicin, dapsone, and clofazimine for 12 months. The Ridley-Jopling five-type classification (TT/BT/BB/BL/LL) adds prognostic detail: which type predicts how likely a patient is to develop reactions (immune complications during or after treatment), how much nerve damage to anticipate, and how contagious the case is. In India, NLEP centres use both systems. WHO for treatment decisions, Ridley-Jopling for clinical description and follow-up planning.

One feature is diagnostic when present: reduced or absent sensation in the patch. A leprosy skin lesion is typically hypopigmented (lighter than surrounding skin) or slightly reddish, has well-defined edges, and, critically, does not feel normal to touch, pinprick, or temperature. Ringworm and eczema itch and burn; leprosy lesions are usually numb or feel dull. To check at home: lightly touch the patch and adjacent normal skin with a wisp of cotton, then repeat with something warm and something cool. If the patch does not sense any of these normally, seek medical evaluation. Other clues: a thickened nerve near the patch that you can feel as a firm cord under the skin (common in the ulnar nerve near the elbow, the great auricular nerve in the neck, or the common peroneal nerve near the knee) is another leprosy-specific finding. Ringworm and eczema do not thicken nerves.

Yes on both counts. India has the largest annual case count in the world, over 100,000 new cases detected each year through NLEP surveillance, concentrated in Bihar, Chhattisgarh, Jharkhand, Odisha, and parts of Maharashtra. And yes, leprosy is completely curable with multidrug therapy, the bacteria are killed within days of starting rifampicin, and full treatment (6-12 months depending on type) prevents relapse. What is not always reversible is the nerve damage and disability that develops before diagnosis, which is why early detection matters more than treatment access. NLEP provides diagnosis and MDT free of charge at every district hospital and most primary health centres, there is no financial barrier to treatment. The barrier is often social: fear of stigma delays presentation.

Casual social contact, sharing a workspace, brief conversations, handshakes, carries very low transmission risk because leprosy requires prolonged close exposure to spread. Household contacts and prolonged close contacts of untreated multibacillary cases have meaningfully elevated risk (roughly 5-10 times general population), which is why NLEP actively traces household contacts. Two protective factors: BCG vaccination in childhood offers partial protection; and once a patient starts multidrug therapy, they become non-infectious within days as the bacteria are killed by rifampicin. If you are a household contact of a diagnosed case, ask about single-dose rifampicin post-exposure prophylaxis (SDR-PEP). WHO now recommends this for close contacts and it reduces subsequent leprosy risk by roughly 50-60%. Do not wait for symptoms; contact tracing is the standard of care.