Type 1 Lepra Reaction
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Direct answer
A Type 1 lepra reaction is a reversal reaction in borderline leprosy, in which rising cell-mediated immunity inflames existing lesions and often involves the nerves. It occurs mainly in the borderline tuberculoid and mid-borderline groups, commonly during or after multidrug therapy. Neuritis is the dangerous feature because it can cause permanent deformity, so early recognition, oral corticosteroids and continued MDT are needed to preserve nerve function.
What you must remember
- Mechanism: an upgrade in cell-mediated immunity against Mycobacterium leprae antigens, producing delayed-type inflammation in lesions that already exist.
- Skin features: existing plaques become red, swollen and tender, and new lesions may appear in the same patient.
- Neuritis: tender, thickened nerves with rapidly developing sensory or motor loss, which can progress to claw hand, foot drop or ulceration if untreated.
- Categories: seen mainly in BT and BB, less commonly in BL, and rare in lepromatous disease.
- Timing: may appear before, during or after multidrug therapy, so patients are warned to report new pain or swelling at any stage.
- Management: continue MDT, start oral corticosteroids early and taper according to the response of the skin and nerves.
- Nerve decompression: considered for severe or steroid-resistant neuritis, ideally before irreversible damage has occurred.
- Distinction from Type 2: erythema nodosum leprosum is a separate reaction in BL and LL with systemic features, not a reversal reaction.
A stepwise approach to a reversal reaction
A patient with borderline leprosy who develops swollen lesions or nerve pain should be assessed without delay. The sequence below keeps nerve damage to a minimum, because the nerves, not the skin, determine long-term disability.
- Recognise: acute inflammation of old lesions, with or without new patches, and nerve tenderness signal a reversal reaction rather than an infection flare.
- Confirm the category: check the classification and the current treatment stage, since borderline categories are the setting for this reaction.
- Assess nerves: test sensation in each lesion, palpate the named nerves and perform voluntary muscle testing for weakness, recording a baseline.
- Start steroids: give oral corticosteroids promptly for neuritis or extensive skin involvement, and taper slowly according to response.
- Continue MDT: keep the multidrug regimen going, because stopping it leaves the bacilli active and the reaction can recur.
- Protect and monitor: check eye closure for lagophthalmos, provide insensitive-limb care and review nerve function regularly.
- Escalate: refer for nerve decompression if neuritis is severe or does not respond to steroids within the expected time.
Early steroid treatment is the single most important step in limiting disability, because nerve damage that has become established responds poorly to later treatment.
Where the exam catches students
Most traps involve misidentifying the reaction or treating the nerves inadequately.
- Trap: labelling every leprosy reaction as ENL Correct: a Type 1 reaction is a reversal reaction in borderline disease, whereas ENL is a Type 2 immune complex reaction in BL and LL with systemic features.
- Trap: stopping MDT during a reversal reaction Correct: MDT continues, and the reaction is managed with steroids alongside it.
- Trap: using NSAIDs alone for painful neuritis Correct: neuritis needs corticosteroids, because NSAIDs relieve pain but do not protect the nerve from damage.
- Trap: waiting for the neuritis to settle before referring Correct: severe or steroid-resistant neuritis needs prompt nerve decompression assessment to prevent permanent deformity.
Frequently asked questions
What is the difference between Type 1 and Type 2 lepra reactions?
Type 1 reactions are reversal reactions in borderline leprosy, caused by rising cell-mediated immunity that inflames existing lesions. Type 2 reactions are erythema nodosum leprosum in lepromatous and borderline lepromatous disease, caused by immune complexes and accompanied by systemic features.
Why is neuritis the most serious feature of a Type 1 reaction?
Neuritis in a Type 1 reaction causes tender, thickened nerves and rapidly developing sensory and motor loss that can become permanent. Early corticosteroid treatment and nerve function assessment are therefore essential to prevent deformities such as claw hand or foot drop.
Should multidrug therapy be stopped during a Type 1 reaction?
Multidrug therapy should not be stopped during a Type 1 reaction, because the reaction reflects an immune response to bacilli that remain present. The reaction is managed with corticosteroids alongside continued MDT.
What is the role of corticosteroids in Type 1 leprosy reactions?
Oral corticosteroids are the mainstay of treatment for Type 1 leprosy reactions, given early and tapered according to the clinical response of the skin and nerves. They reduce inflammation and protect nerve function while the underlying multidrug therapy continues.