Leprosy

Leprosy is a chronic bacterial infection due to Mycobacterium leprae.

It is transmitted by frequent close contact, mainly between household members.

It mainly affects young adults. 94% of reported cases globally were in Bangladesh, Brazil, Democratic Republic of Congo, Ethiopia, India, Indonesia, Madagascar, Myanmar, Nepal, Nigeria, the Philippines, Sri Lanka and the United Republic of Tanzania. [1] Citation 1. World Health Organization. Global Leprosy Programme. Global leprosy strategy 2016-2020. Accelerating towards a leprosy-free world, 2016.
http://apps.who.int/iris/bitstream/handle/10665/208824/9789290225096_en.pdf?sequence=14&isAllowed=y [Accessed 17 October 2018]

Clinical features

Leprosy should be considered in any patient presenting with:

• Hypopigmented or erythematous skin lesion(s) with partial or complete loss of sensation to touch, pain, heat; 
• Infiltrated pigmented nodules, initially with no sensory loss, on the face, ear lobes and the upper and lower limbs;
• Tender, infiltrated and hypertrophied peripheral nerve (ulnar, radial, median, popliteal, tibial etc.) with possible paraesthesia of the extremities, trophic changes (perforating ulcer of the foot) or paralysis (steppage gait, deformaties of hands and feet, facial nerve paralysis).

There are different clinical forms and classification systems of leprosy.

Ridley-Jopling classification 

This classification differentiates 5 forms based on the bacteriological index. These forms correlate with the immunological response to  M. leprae. Patients with tuberculoid leprosy (TT) are resistant to the bacillus and infection is localised. Patients with lepromatous leprosy (LL) are extremely sensitive to the bacillus and the infection is disseminated. Borderline forms (BT, BB, BL) are between the two ends of the spectrum (TT and LL).

WHO classification

In order to simplify diagnosis and to promote rapid implementation of treatment, the WHO has simplified clinical classification of leprosy and differentiates only 2 forms:

• Multibacillary leprosy: more than 5 skin lesions
• Paucibacillary leprosy: 1 to 5 skin lesions

Multibacillary leprosy includes LL, BL and BB forms and paucibacillary leprosy includes the TT and BT forms of the Ridley-Jopling classification system.

Laboratory

• Laboratory diagnosis is based on the detection of acid-fast bacilli in a Ziehl-Neelsen stained nasal smear and skin-split smear taken from the ear lobe or from a skin lesion. In TT leprosy bacilli are not found.
• In practice, in most endemic countries diagnosis is based on the WHO clinical classification (number of lesions).

Treatment

Countries where leprosy is endemic have a control programme. Check national recommendations.

First-line treatment regimens recommended by the WHO

Note: the monthly doses of rifampicin and clofazimine are administered under direct observation by medical staff whereas the daily doses of clofazimine and dapsone are taken by the patient at home. Rifampicin should be taken on an empty stomach to improve absorption.

Teach the patient to recognise and quickly report a lepra reaction or relapse in order to modify or restart treatment.

Leprosy reactions

These reactions usually occur during the course of treatment in patients with multibacillary leprosy (BL and LL). They are associated with the immunological response to M. leprae antigens. Urgent treatment is required to avoid irreversible disability. Do not interrupt ongoing leprosy treatment. 

Clinical features

• Reversal reactions: 
  • Exacerbation of the skin lesions that become erythematous and oedematous and risk or ulceration. Onset or worsening of numbness of skin lesions; 
  • Onset of acute painful hypertrophic neuritis.

• Erythema nodosum leprosum:
  • Fever, asthenia, alteration of the general state;
  • Crops of purplish-red, tender subcutaneous nodules, warmer than the surrounding skin. 

Treatment

• Reversal reactions: 
  prednisolone (or prednisone) PO: 0.5 to 1 mg/kg once daily for 2 weeks. Re-examine the patient every 2 weeks and decrease the dosage if the neurological signs recede. According to clinical response, treatment may last 3 to 6 months. [2] Citation 2. World Health Organization. WHO Expert Committee on Leprosy. Eighth report. WHO technical report series, n° 968. Geneva, 2012.
  http://www.searo.who.int/entity/global_leprosy_programme/publications/8th_expert_comm_2012.pdf [Accessed 17 October 2018]
  For example, for an adult: [3] Citation 3. World Health Organization. A guide to eliminating leprosy as a public health problem. Leprosy Elimination Group, 2000.
  http://apps.who.int/iris/bitstream/handle/10665/66612/WHO_CDS_CPE_CEE_2000.14.pdf?sequence=1 [Accessed 17 October 2018]  
  Week 1 and 2: 40 mg once daily 
  Week 3 and 4: 30 mg once daily 
  Week 5 and 6: 20 mg once daily 
  Week 7 and 8: 15 mg once daily 
  Week 9 and 10: 10 mg once daily 
  Week 11 and 12: 5 mg once daily

• Erythema nodosum leprosum:
  • prednisolone (or prednisone) PO as for reversal reactions, for 3 months. [2] Citation 2. World Health Organization. WHO Expert Committee on Leprosy. Eighth report. WHO technical report series, n° 968. Geneva, 2012.
    http://www.searo.who.int/entity/global_leprosy_programme/publications/8th_expert_comm_2012.pdf [Accessed 17 October 2018]  
  • Fever: paracetamol PO (see Fever, Chapter 1)