SN5 SHORT NOTE 5M ★ High-yield

Describe the lepra reactions with their types, features and management.

Microbiology · 2nd Professional — Para-Clinical

Definition

Lepra reactions are acute episodes of inflammation occurring during the chronic course of leprosy, caused by a sudden change in the immunological balance between host and bacillus. They are the principal cause of nerve damage and permanent disability.

Feature	Type 1 — reversal reaction	Type 2 — erythema nodosum leprosum
Immunology	Type IV cell-mediated (delayed) hypersensitivity — a sudden increase in cell-mediated immunity	Type III immune complex hypersensitivity, with complement activation and neutrophil infiltration
Occurs in	Borderline forms — BT, BB, BL (the immunologically unstable part of the spectrum)	Lepromatous and borderline lepromatous (LL, BL) — where the antigen load is high
Skin	Existing lesions become red, swollen, warm and tender; no new lesions	Crops of new, tender, red subcutaneous nodules appearing anywhere, including on previously normal skin
Systemic features	Usually absent or mild	Prominent — fever, malaise, arthralgia, iritis, orchitis, neuritis, lymphadenitis, nephritis
Nerve involvement	Sudden, severe and the dominant feature — pain, tenderness and rapid loss of function; a medical emergency	Neuritis occurs but is usually less abrupt
Timing	Often in the first 6 months of treatment, or in pregnancy and the puerperium	Usually after some months of treatment; tends to recur over years
Treatment	Corticosteroids — prednisolone, tapered over months	Thalidomide (highly effective but teratogenic); corticosteroids; clofazimine in high dose

CLINICAL PEARL

A reaction is not treatment failure, and stopping the antileprosy drugs is the wrong response. Reactions commonly begin after treatment starts, precisely because killed bacilli release antigen and the immune balance shifts — which patients and inexperienced clinicians read as the drugs "not working" or "causing harm". Multidrug therapy must be continued and the reaction treated alongside it, because it is the reaction, not the infection, that is destroying the nerve.

Recognition and Management

Assess nerve function at every visit — voluntary muscle testing and sensory testing of the hands, feet and eyes; deterioration is the indication for urgent treatment
Type 1 reaction with neuritis is an emergency — prednisolone started at once, typically 40 to 60 mg daily and tapered over 12 to 24 weeks; delay of even days may cause irreversible nerve damage and permanent deformity
Rest the affected limb and splint it; analgesia for pain
Type 2 (ENL) — mild episodes respond to analgesics and clofazimine; severe or recurrent episodes require thalidomide, which is dramatically effective. It must never be given to a woman of childbearing potential without a strict pregnancy prevention programme, given its history
Treat the eye — iritis requires urgent topical steroids and mydriatics; untreated it causes blindness
Continue multidrug therapy throughout the reaction

The Lucio Phenomenon and Differential Diagnosis

LUCIO phenomenon — a rare severe necrotising vasculitis occurring in diffuse non-nodular lepromatous leprosy, with painful irregular purpuric lesions that ulcerate; it carries a high mortality and requires steroids and full multidrug therapy
Differential diagnosis of type 2 reaction — erythema nodosum from other causes (tuberculosis, streptococcal infection, sarcoidosis, drugs, inflammatory bowel disease), other panniculitides, and vasculitis
Distinguish a reaction from relapse — a reaction is acute with inflammation and pain, whereas relapse is insidious, painless, with new lesions appearing slowly and a rising bacteriological index. Relapse requires retreatment; a reaction requires anti-inflammatory treatment

Applied Aspects

Warn every patient about reactions before starting treatment, and tell them to return immediately if a lesion becomes red or painful, or if there is numbness or weakness; this single instruction prevents much permanent disability
Do not stop multidrug therapy for a reaction, and do not interpret the reaction as drug allergy
Nerve function assessment must be routine, not occasional; silent neuropathy occurs and is detected only by testing
Steroids are given for months, not days, and premature tapering causes rebound; the patient needs monitoring for steroid adverse effects, including hyperglycaemia and infection
Thalidomide is available in India under restricted conditions, and its use demands documented contraception and counselling; the drug that caused the greatest disaster in the history of pharmacology is also the best treatment for this condition
Disability from leprosy is almost entirely preventable, and is a marker of delayed diagnosis or untreated reactions rather than of the infection itself

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