References:
- Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
| Agent | BACTERIUM. Mycobacterium leprae. An acid-fast bacillus |
| Reservoir | Human Armadillo (unsure) |
| Vector | None |
| Vehicle | Patient secretions |
| Incubation Period | 3 to 5 years (As early or late as 3 months to 40 years) |
| Diagnostic Tests | Visualization of organisms in exudate, scrapings or biopsy Nucleic acid amplification |
| Typical Adult Therapy | Multibacillary: One year therapy Dapsone 100 mg + Clofazimine 50 mg daily; and, Rifampin 600 mg + Clofazimine 300 mg once monthly Paucibacillary: Six month therapy Dapsone 100 mg daily; and Rifampin 600 mg once monthly |
| Typical Pediatric Therapy | Multibacillary: One year therapy Dapsone 1 to 2 mg/kg + Clofazimine 1 mg/kg daily; and, Rifampin 10 mg/kg + Clofazimine 1 mg/kg once monthly Paucibacillary: Six month therapy Dapsone 1 to 2 mg/kg daily; and Rifampin 10 mg/kg once monthly |
| Clinical Hints | Anesthetic, circinate hypopigmented skin lesions and thickened peripheral nerves (tuberculoid leprosy); or diffuse, destructive papulonodular infection (lepromatous leprosy); or combined/intermediate forms. |
| Synonyms | Aussatz, Doence de Hansen, Hansen’s disease, Lebbra, Lepra, Mycobacterium leprae, Mycobacterium lepromatosis. |
WHO Case Definition for Surveillance
Clinical description: the clinical manifestations of the disease vary in a continuous spectrum between the two polar forms, lepromatous and tuberculoid leprosy:
- In lepromatous (multibacillary) leprosy, nodules, papules, macules and diffuse infiltrations are bilateral symmetrical and usually numerous and extensive; involvement of the nasal mucosa may lead to crusting, obstructed breathing and epistaxis; ocular involvement leads to iritis and keratitis
- In tuberculoid (paucibacillary) leprosy, skin lesions are single or few, sharply demarcated, anesthetic or hypoesthesic, and bilateral asymmetrical, involvement of peripheral nerves tends to be severe
- Borderline leprosy has features of both polar forms and is more labile
- Indeterminate leprosy is characterized by hypopigmented maculae with ill-defined borders; if untreated, it may progress to tuberculoid, borderline or lepromatous disease.
Laboratory criteria for confirmation
- Alcohol-acid-fast bacilli in skin smears (made by the scrape-incision method).
- In the paucibacillary form the bacilli may be so few that they are not demonstrable.
- In view of the increasing prevalence of HIV and hepatitis B infection in many countries where leprosy remains endemic, the number of skin smear sites and the frequency of smear collection should be limited to the minimum necessary.
WHO Operational Case Classification Definitions
A case of leprosy is defined as a person showing one or more of the following features, and who as yet has to complete a full course of treatment:
- Hypopigmented or reddish skin lesions with definite loss of sensation
- Involvement of the peripheral nerves, as demonstrated by definite thickening with loss of sensation
- Skin smear positive for acid-fast bacilli
Classification (microbiological):
- Paucibacillary (PB): includes all smear-negative cases.
- Multibacillary (MB): includes all smear-positive cases.
Classification (clinical): 3. Paucibacillary single lesion leprosy: 1 skin lesion. 4. Paucibacillary leprosy: 2 to 5 patches or lesions on the skin. 5. Multibacillary leprosy: >5 patches or lesions on the skin.
The major forms of leprosy are as follows:
- Tuberculoid: one or a few well-demarcated, hypopigmented, and anesthetic skin lesions, frequently with active, spreading edges and a clearing center; peripheral nerve swelling or thickening also may occur.
- Lepromatous: a number of erythematous papules and nodules or an infiltration of the face (including oral mucosa, hands, and feet with lesions in a bilateral and symmetrical distribution that progress to thickening of the skin.
- Borderline (dimorphous): skin lesions characteristic of both the tuberculoid and lepromatous forms.
- Indeterminate: early lesions, usually hypopigmented macules, without developed tuberculoid or lepromatous features.
Relapsing disease may manifest as lymphadenopathy mimicking tuberculosis 4
- Relapses may follow effective antimicrobial therapy.
The skin lesions of paracoccidioidomycosis may mimic those of tuberculoid leprosy.
- Lepromatous leprosy may mimic sarcoidosis.
- Lupus vulgaris may mimic actinomycosis or mycetoma.
- Diffuse cutaneous leishmaniasis may mimic lepromatous leprosy. The lesions of both cutaneous and mucocutaneous leishmaniasis could be mistaken for those of borderline tuberculoid leprosy.
- Leprosy may be initially misdiagnosed as adult stills disease or an auto-immune disorder.
Leprosy may be associated with endocrine dysfunction including hypogonadism, sterility and osteoporosis
Six percent of leprosy patients exhibit rheumatological manifestations, most commonly resembling rheumatoid arthritis
- Rare instances of spondylodiscitis have been reported.
Lucio’s phenomenon is a rare and aggressive necrotizing variant of erythema nodosum leprosum that classically occur in patients with undiagnosed, diffuse non-nodular lepromatous leprosy.
Erythema multiforme is occasionally encountered among patients with leprosy.
Chronic skin lesions may undergo malignant transformation.
Cranial nerve involvement, most often trigeminal and facial, is not uncommon.
- Segmental necrotizing granulomatous neuritis is reported in some cases.