How is painful neuropathy caused by leprosy treated?

Management of Painful Neuropathy in Leprosy

Painful neuropathy in leprosy should be treated with a combination of corticosteroids as first-line therapy, followed by anticonvulsants or antidepressants for persistent neuropathic pain. This approach addresses both the inflammatory and neuropathic components of leprosy-related nerve damage.

Pathophysiology and Diagnosis

Leprosy causes nerve damage through:

• Perineural inflammation (hallmark of early leprosy)
• T cell-mediated inflammatory processes
• Direct invasion of Schwann cells by Mycobacterium leprae
• Immune-mediated reactions (Type 1 "Reversal" and Type 2 "ENL")

Diagnosis requires:

• Assessment for sensory loss, motor weakness, and nerve enlargement
• Skin lesions with sensory changes (though pure neuritic forms occur in 10% of cases)
• Nerve conduction studies showing axonal neuropathy patterns
• Nerve biopsy in unclear cases (showing microvasculitis or granulomas)

Treatment Algorithm

Step 1: Control Acute Inflammation

• Corticosteroids (First-line therapy)
  • Prednisolone 40-60mg daily for 12 weeks with gradual taper
  • Hospitalization for severe reactions with neuritis
  • Continue anti-leprosy treatment during reactions 1
  • Approximately 50% of patients may relapse and require additional steroid courses 2

Step 2: Manage Persistent Neuropathic Pain

For pain persisting after inflammation control:

• First-line medications:

  • Anticonvulsants:

    • Pregabalin: Start 50-75mg BID, target 300-600mg/day
    • Gabapentin: Start 100-300mg daily, target 900-3600mg/day

  • Antidepressants:

    • Duloxetine: Start 30mg daily for 1 week, increase to 60mg daily (therapeutic dose) 3
    • Tricyclic antidepressants: Start 10-25mg at bedtime, target 75mg/day (not exceeding 100mg) 4

Step 3: Refractory Pain Management

• Second-line options:
  • Tramadol (NNT 4.7)
  • Consider referral to pain specialist for combination therapy
  • Surgical decompression of swollen nerve trunks in select cases 1

Special Considerations

Leprosy Reactional States

• Type 1 (Reversal) Reaction:

  • Occurs in borderline/tuberculoid leprosy
  • Presents with swelling of existing skin and nerve lesions
  • Management: High-dose steroids, continue anti-leprosy treatment 1

• Type 2 (ENL) Reaction:

  • Occurs mainly in lepromatous patients
  • Presents with fever, tender erythematous nodules, neuritis
  • Management: Steroids, analgesics, continue anti-leprosy treatment 1

Monitoring and Follow-up

• Regular assessment of nerve function (sensory and motor)
• Monitor for steroid side effects
• Long-term follow-up as neuropathy may develop years after successful treatment of infection 5

Important Caveats

• Up to 60% of multibacillary patients have clinically apparent nerve damage at diagnosis
• 30% develop further nerve damage during treatment
• 10% may develop new nerve damage after completing drug treatment 2
• Antibiotics used to treat M. leprae have little effect on nerve damage as it is immune-mediated
• Leprosy Late-Onset Neuropathy (LLON) can occur years (average 19 years) after successful treatment 5
• Neuropathic pain in leprosy is often underrecognized and undertreated 6

Remember that leprosy should be viewed as a chronic neurological condition rather than simply a skin disease 2. Early detection and prompt treatment of nerve involvement are critical to prevent long-term disability, even after successful eradication of the bacteria.