Leprosy Reactions
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Direct answer
Leprosy reactions are acute inflammatory episodes superimposed on chronic Mycobacterium leprae infection, and they are the commonest cause of new nerve damage and deformity. Type 1 (reversal) reaction is a delayed-hypersensitivity response seen in borderline cases, producing inflamed skin patches and tender nerves; it is treated with oral corticosteroids. Type 2 reaction, erythema nodosum leprosum (ENL), is an immune-complex phenomenon of lepromatous leprosy, treated with thalidomide or steroids. Multidrug therapy is never stopped during a reaction.
What you must remember
- Type 1 (reversal, upgrading) reaction: existing borderline lesions become red, oedematous and desquamating; nerves — classically the ulnar, median, lateral popliteal (common peroneal) and facial — turn tender and thickened with rapid loss of sensation and motor power; treat with prednisolone (commonly 40 to 60 mg daily, tapered over 12 to 24 weeks).
- Type 2 reaction (ENL): crops of tender subcutaneous nodules on face and extensor surfaces in lepromatous and borderline lepromatous disease, with fever, neuritis, iritis, orchitis, dactylitis, glomerulonephritis and high ESR; first line is thalidomide (100 to 400 mg daily — absolutely contraindicated in pregnancy) or corticosteroids, with clofazimine as a steroid-sparing agent for recurrent disease.
- Nerve damage: ulnar nerve at the elbow is the most frequently involved; post-auricular nerve enlargement helps diagnosis; claw hand, foot drop, ape thumb and lagophthalmos follow.
- Never interrupt multidrug therapy (rifampicin, dapsone, clofazimine per WHO paucibacillary or multibacillary schedules) — reactions are treated in addition.
- Dapsone may cause haemolysis, methaemoglobinaemia and the rare dapsone hypersensitivity syndrome, which can itself mimic a reaction.
- Reactions may appear before, during or after MDT; reactions after treatment completion still need full anti-reaction therapy.
- Physiotherapy, splinting and self-care of anaesthetic hands and feet prevent plantar ulcers and secondary deformity.
Sorting one reaction from the other at the bedside
Two patients in the same leprosy clinic, two different emergencies. The first is a borderline case three months into multidrug therapy whose pre-existing patch has turned red, swollen and desquamating, with a tender thickened ulnar nerve and new finger-abduction weakness — a type 1 (reversal) reaction threatening the nerve right now. Start prednisolone 40 to 60 mg daily, tapered over 12 to 24 weeks, and document sensory and motor testing at each visit, because the window for saving the nerve is short. The second is a lepromatous patient who develops crops of tender subcutaneous nodules on the face and extensor surfaces with fever, neuritis, iritis, orchitis and a high ESR — erythema nodosum leprosum, an immune-complex phenomenon of high-bacillary disease. First line is thalidomide 100 to 400 mg daily, strictly contraindicated in pregnancy (in a woman of childbearing age, corticosteroids carry the load, with clofazimine as the steroid-sparing agent), and the systemic complications — glomerulonephritis among them — need watching. In both patients the reflex action that must be resisted is stopping MDT: rifampicin, dapsone and clofazimine continue unchanged, and anti-reaction treatment is layered on top. After either reaction, physiotherapy, splinting and self-care of anaesthetic hands and feet prevent the claw hand, foot drop, ape thumb, lagophthalmos and plantar ulcers; reactions may even appear after MDT is complete, still requiring full anti-reaction therapy.
How the exam frames leprosy reactions
The vignette contrast is the reliable format: an inflamed existing patch with foot drop versus fever with fresh nodules, and the drug matching — prednisolone for type 1, thalidomide for ENL with its pregnancy contraindication as the twist — follows directly. The ulnar nerve at the elbow is the most frequently involved and the expected one-liner, with lateral popliteal (foot drop), median, facial and post-auricular enlargement completing the set. The assertion-reason favourite is that MDT continues through reactions, and the adjacent trap is calling a reaction "treatment failure" — relapse means reappearance of active lesions after adequate therapy with bacteriological proof. One pharmacology crossover:
Frequently asked questions
What distinguishes type 1 from type 2 leprosy reactions?
Type 1 is a cell-mediated reaction inflaming existing borderline lesions with neuritis; type 2 (ENL) is immune-complex driven, causing new nodules with fever in lepromatous disease.
What is the treatment of type 1 reaction?
Oral prednisolone, commonly 40 to 60 mg daily tapered over months, with urgent attention to nerve function; clofazimine helps chronic cases.
What is the drug of choice for erythema nodosum leprosum?
Thalidomide, 100 to 400 mg daily — strictly contraindicated in pregnancy because of teratogenicity; corticosteroids or clofazimine are alternatives.
Which nerve is most commonly affected in leprosy?
The ulnar nerve at the elbow, producing claw hand; the lateral popliteal nerve causing foot drop is the other classic.
Is MDT stopped during a reaction?
No — multidrug therapy continues unchanged; anti-reaction drugs are added on top.
Why are reactions clinically important?
They are the chief cause of acute nerve damage and hence deformity, so prompt recognition and steroids prevent irreversible disability.