In a leprosy patient receiving multidrug therapy, what is the typical timing of type 1 (reversal) and type 2 (erythema nodosum leprosum) reactions, and what are the first‑line treatments for each?

Type 1 and Type 2 Leprosy Reactions: Timeline and Management During MDT

Timing of Reactions in Relation to MDT

Type 1 reversal reactions occur most frequently during the first year of MDT (26.3% of BL patients, 12.8% of LL patients), with risk declining gradually but reactions still possible up to 4-6 years after starting treatment, while Type 2 reactions (ENL) occur less commonly and later, primarily during the first year of MDT (5.5% of LL patients) and continuing through the second year. 1, 2

Type 1 Reversal Reactions Timeline

• Pre-treatment presentation: 4.9% of borderline lepromatous (BL) patients and 3.4% of borderline tuberculoid (BT) patients present with reversal reactions at the time of leprosy diagnosis, before MDT initiation 1, 3

• First month of MDT: 50% of skin reactions developing during treatment occur within the first month after starting MDT 3

• First year of MDT: This represents the highest-risk period, with 26.3% of BL patients and 10.3% of BT patients developing reversal reactions 1

• Second year of MDT: Risk declines to 12.4% in BL patients and continues in BT patients 1

• Post-MDT period: 7.3% of BT patients develop reactions during the first year after completing MDT, with late reactions documented up to 6.5 years after treatment initiation 1, 3

• Critical distinction: Neurological reactions occur later and over a longer time course compared to skin reactions 3

Type 2 Reactions (ENL) Timeline

• Pre-treatment: 2.8% of LL patients present with ENL at diagnosis 1

• First year of MDT: 5.5% of LL patients develop ENL, representing the peak incidence period 1

• Second year of MDT: 2.8% of LL patients experience ENL 1

• Overall incidence: ENL occurs in 11.1% of LL patients by the end of the second year of MDT, compared to only 2.7% of BL patients 1

• Post-MDT complications: Patients completing 1-year MDT experience significantly more reactions (27% vs 8%) during the first year after treatment completion compared to those who received 2-year MDT 2

First-Line Treatment for Type 1 Reversal Reactions

Corticosteroids, specifically prednisolone, are the first-line treatment for Type 1 reversal reactions while continuing MDT without interruption. 4, 5, 6

Treatment Protocol

• Continue MDT: Treatment with multidrug therapy must not be interrupted due to reversal reactions; reactions require anti-inflammatory management while maintaining antimicrobial therapy 4, 5

• Prednisolone dosing: Initiate oral prednisolone for nerve function loss and inflammatory exacerbation of skin lesions 1, 6

• Treatment outcomes: 88.2% of patients treated with prednisolone for nerve function loss achieve complete or partial recovery, while 11.8% show no improvement 1

• Timing is critical: Early recognition and treatment of reversal reactions is imperative to prevent permanent nerve damage and disability 7

Clinical Monitoring

• Assess for neuritis: Reversal reactions are the most common cause of nerve damage in leprosy, requiring immediate corticosteroid intervention 6, 7

• Monitor for recurrence: 31.8% of patients experience repeated reactional episodes, necessitating ongoing surveillance 3

• Distinguish from treatment failure: Leprosy reactions must be differentiated from inadequate antimicrobial therapy; reactions indicate immune response, not treatment failure 5

First-Line Treatment for Type 2 Reactions (ENL)

Thalidomide is the first-line treatment for erythema nodosum leprosum, with prednisone as an alternative or adjunctive therapy, while continuing MDT. 6

Treatment Approach

• Thalidomide: Primary agent for ENL management, though availability may be limited due to teratogenicity concerns 6

• Prednisone: Used when thalidomide is contraindicated or unavailable, or as adjunctive therapy for severe cases 6

• Continue MDT: As with Type 1 reactions, antimicrobial therapy must not be interrupted during ENL episodes 4, 5

• Monitor for neuritis: ENL may also lead to nerve damage requiring prompt intervention 6

Critical Pitfalls to Avoid

• Never discontinue MDT during reactions: Premature treatment interruption due to leprosy reactions worsens outcomes; reactions require anti-inflammatory therapy while continuing antimicrobial treatment 4, 5

• Recognize late reactions: Reactions can occur years after starting treatment (up to 6.5 years), requiring sustained vigilance even after MDT completion 1, 3

• Higher risk with shorter MDT: Patients completing 1-year MDT experience significantly more frequent, severe, and prolonged reactions compared to 2-year MDT recipients (27% vs 8% in first post-treatment year) 2

• Neurological reactions differ from skin reactions: Nerve involvement occurs later and over a longer time course, requiring different monitoring strategies 3

• Repeated episodes are common: 31.8% of patients experience multiple reactional episodes, necessitating ongoing treatment readiness 3