Leprosy
A chronic bacterial infection of the skin and nerves caused by M. leprae, leading to numb skin patches and potential limb deformities if untreated.
Emergency Management: Acute severe neuritis threatening permanent nerve damage requires immediate high-dose systemic corticosteroids (e.g., Prednisone 40-60 mg/day) to prevent permanent paralysis.
Leprosy is a chronic granulomatous infectious disease caused by the obligate intracellular bacillus Mycobacterium leprae. It primarily affects the skin, peripheral nerves, upper respiratory tract mucosa, and eyes, potentially leading to progressive and permanent disabilities.
Detailed Overview
Leprosy exhibits a clinical spectrum depending on the hosts cellular immune response. Tuberculoid leprosy (paucibacillary) involves a strong cellular immune response, presenting with few skin lesions and localized nerve involvement. Lepromatous leprosy (multibacillary) is characterized by a weak cellular response, leading to widespread skin lesions, leonine facies, and symmetric nerve damage. Though largely eliminated globally as a public health problem, it remains endemic in regions like India, Brazil, and Indonesia. Treatment requires prolonged multi-drug therapy (MDT).
Epidemiology & Demographics
Global prevalence is around 200,000 cases annually, primarily in India (accounts for >60%), Brazil, and Indonesia. In the US, 150-250 cases are reported annually, often associated with exposure to armadillos in southern states. Affects all ages, but peak incidence is between 20-30 years.
Etiological Mechanism
Infection by Mycobacterium leprae, a slow-growing, acid-fast bacillus that prefers cooler body temperatures (27-30C). Transmission is likely via respiratory droplets during prolonged close contact.
Primary Causes
Infection primarily through respiratory droplets from untreated multibacillary patients. Zoonotic transmission from nine-banded armadillos is recognized in the Americas.
M. leprae invades Schwann cells of the peripheral nervous system and macrophages in the skin. The bacilli bind to laminin-2 on Schwann cells, causing demyelination and axonal dysfunction (loss of sensation, weakness). The clinical manifestation is dictated by the Th1 vs Th2 immune response. A Th1 response (IL-2, IFN-gamma) forms granulomas that contain the infection (Tuberculoid leprosy). A Th2 response (IL-4, IL-10) fails to control bacterial replication, allowing massive bacillary dissemination (Lepromatous leprosy).
Diagnostic Criteria & Guidelines
Diagnosis requires at least one of the cardinal signs: 1) Hypopigmented/reddish patch with definite loss of sensation; 2) Thickened peripheral nerve with loss of sensation/weakness; 3) Positive slit-skin smears for acid-fast bacilli.
WHO Multi-Drug Therapy (MDT). For Multibacillary (MB): Rifampin 600 mg once monthly, Clofazimine 300 mg once monthly + 50 mg daily, and Dapsone 100 mg daily for 12 months. For Paucibacillary (PB): Rifampin 600 mg once monthly and Dapsone 100 mg daily for 6 months.
Second-Line & Adjunctive Therapy
For MDT resistance or severe toxicity: Ofloxacin 400 mg daily + Minocycline 100 mg daily + Clarithromycin 500 mg daily for 6-12 months.
Surgical & Procedural Management
Nerve decompression for acute neuritis unresponsive to steroids. Tendon transfers to correct foot drop or claw hands. Amputation of non-healing, osteomyelitis-infected digits.
Patient Counseling & Advice
Inform the patient that they are non-infectious within 72 hours of starting MDT, hence no isolation is needed. Warn about Clofazimine causing reversible red/brown skin discoloration. Emphasize that treatment cures the infection but may not reverse existing nerve damage.
Follow-Up & Monitoring Schedule
Monthly clinical check for first 6 months, monitoring for lepra reactions (Type 1 and 2). Routine neurologic exam mapping sensory loss via monofilament testing.
Preventive Strategies
Contact tracing and screening of household contacts. Single-dose Rifampicin (SDR) prophylaxis for close contacts is recommended by WHO.
Excellent for curing the infection with MDT (cure rate >95%). However, morbidity remains high due to irreversible neuropathy if treated late.