Diagnosis

Leporsy

Etiology

Cause [eya][6aj]

• A chronic granulomatous infection caused by the acid-fast, rod-shaped bacillus Mycobacterium leprae complex

• The route of transmission is most likely human-to-human aerosol spread of nasal secretions

Pathophysiology [eya][6aj]

1. Leprosy can manifest in different forms, depending on the host response:

   • Strong cellular immune response -> Tuberculoid form:

     • Limited dry and hypoesthetic skin lesions (< 5 skin lesions)

     • Asymmetric nerve involvement

     • Low number of bacteria (absence of organisms on smear)

   • Minimal cellular immune response -> Lepromatous form:

     • Extensive skin involvement with infiltrated nodules/plaques (>6 lesions)

     • Symmetric nerve involvement

     • Large number of bacteria found in the lesions (bacilli on smear)

   • Most patients fall into the intermediate classifications, which include borderline tuberculoid leprosy, midborderline leprosy, and borderline lepromatous leprosy

2. Neuropathy: M. leprae affect peripheral nerve cells (Schwann cells) --> nerve demyelination --> loss of axonal conductance --> paresthesia with numbness

3. Ophthalmic Injury: cranial nerve palsies, lagophthalmos, corneal abrasion and ulceration, and drying

Risk factors [eya]

• Close Contact with a patient with leprosy

• Armadillo Exposure

• Old age

• Genetic Influences

• Immunosuppression

Complications [eya]

• Abscesses on nerves

• Blindness

• Neuropathy

• Erythema nodosum leprosum

Epidemiology

Incidence per 100.000 [gt8][hhi][ukq][cas][wv7][ps7][ime]

Approach

• Blood test

• Tissue/skin smear bacilloscopy (acid-fast bacilli in fluid from a lesion) [gt8]

• Skin biopsy (full dermal thickness taken from an edge of the lesion)

• Nasal smears

• Serology (glycolipid-1 specific for M leprae)

• PCR [eya]

• Nerve biopsy

Treatment

1. BCG vaccine prophylaxis: protection varying from 20% to 80% [gt8]

2. Tuberculoid disease: Multidrug therapy regimen for 12 months [eya]

   • Dapsone: 1.5 mg/ kg/day

   • Rifampicin: 10 mg/kg/day

3. Lepromatous disease: Multidrug therapy regimen for 24 months [gt8][6aj]

   • Dapsone: 1.5 mg/ kg/day

   • Rifampicin: 10 mg/kg/day

   • Clofazimine: 1 mg/kg/day

Differential diagnoses

Contact dermatitis, Drug eruptions, Fungal infection, Granuloma annulare, Insect Bite, Keloid, Leishmaniasis, Mycosis fungoides, Neurofibromatosis, Onchocerciasis, Pinta, Pityriasis rosea, Pityriasis versicolor, Polyarteritis nodosa, Psoriasis, Sarcoidosis, Scabies, Syphilis, Systemic lupus erythematosus, Tinea versicolor, Vitiligo, Xanthomas