Mycobacterium leprae: Difference between revisions
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Mycobacterium leprae
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== Clinical Presentation == |
== Clinical Presentation == |
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+ | * Following exposure, about 95% clear it spontaneously |
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− | * Incubation period of 3-5 years (with wide range) |
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+ | * For those who do not, there is an incubation period of 3-5 years (with wide range) that is usually followed by indeterminate leprosy |
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+ | ** Single, ill-defined, hypopigmented skin lesion |
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+ | ** About 75% sponetaneously resolve, with the other 25% progressing |
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* Classic presentation is anaesthetic hypopigmented skin lesion with thickened nerves |
* Classic presentation is anaesthetic hypopigmented skin lesion with thickened nerves |
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+ | |||
− | * Clinical spectrum from tuberculoid, paucibacillary disease to lepromatous, multibacillary disease |
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+ | === Spectrum of disease === |
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+ | * Clinical spectrum can be classified based on the number of lesions and burden of mycobacteria |
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** '''Paucibacillary (PB)''' disease has 1 to 5 skin lesions, without bacilli on skin slit smear |
** '''Paucibacillary (PB)''' disease has 1 to 5 skin lesions, without bacilli on skin slit smear |
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** '''Multibacillary (MB)''' disease has more than 5 skin lesions, with or without nerve involvement or bacilli on slit-skin smear (regardless of number of lesions) |
** '''Multibacillary (MB)''' disease has more than 5 skin lesions, with or without nerve involvement or bacilli on slit-skin smear (regardless of number of lesions) |
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+ | * Can also be classified based on general clinical appearance |
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+ | ** '''Tuberculoid leprosy (TT)''' corresponds to paucibacillary |
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+ | ** '''Borderline tuberculoid leprosy (BT)''' |
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+ | ** '''Borderline leprosy (BB)''' |
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+ | ** '''Borerdline lepromatous leprosy (BL)''' |
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+ | ** '''Lepromatous leprosy (LL)''' corresponding to multibacillary disease |
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+ | |||
+ | === Type I reaction === |
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+ | * A cell-mediated hypersensitivity reaction that can develop in the course of treatment |
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+ | * Also known as a '''reversal reaction''' due to the apparent worsening of the lesion |
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+ | * Occurs most commonly in the borderline cases and may signal progression to the cell-mediated tuberculoid end of the clinical spectrum |
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+ | |||
+ | === Type 2 reaction === |
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+ | * A humorally-mediated hypersensitivity reaction that can develop in the course of treatment |
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+ | * Also known as '''erythema nodosum leprosum''' |
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+ | * Characterized by systemic illness and immune-complex deposition that appears as groups of tender subcutaneous nodules |
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+ | * May have other signs of vasculitis, including fevers, arthralgias, neuralgia, lymphadenopathy, orchitis, and dactylitis |
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== Management == |
== Management == |
Revision as of 09:41, 27 November 2019
Background
Microbiology
Epidemiology
- About 1 million cases worldwide each year, but is rare in North America
- Number may be underestimated due to difficulties with reliable diagnosis
- Most commonly occurs in Southeast Asia (especially India) and Brazil
- Decreasing incidence over the past several decades, likely due to short-course multidrug therapy starting in 1982
- Humans are thought to be the main reservoir, but it has been found in animals as well (particularly armadillos)
- Transmitted most likely by respiratory droplets, though can also be transmitted by direct contact, transplacentally, through breast milk, and after animal exposure
Risk Factors
- Age, with peaks in adolescence and ≥30 years
- Adult men (compared to adult women)
- Duration of contact with an infected patient, and the burden of bacilli in the patient
Pathophysiology
Clinical Presentation
- Following exposure, about 95% clear it spontaneously
- For those who do not, there is an incubation period of 3-5 years (with wide range) that is usually followed by indeterminate leprosy
- Single, ill-defined, hypopigmented skin lesion
- About 75% sponetaneously resolve, with the other 25% progressing
- Classic presentation is anaesthetic hypopigmented skin lesion with thickened nerves
Spectrum of disease
- Clinical spectrum can be classified based on the number of lesions and burden of mycobacteria
- Paucibacillary (PB) disease has 1 to 5 skin lesions, without bacilli on skin slit smear
- Multibacillary (MB) disease has more than 5 skin lesions, with or without nerve involvement or bacilli on slit-skin smear (regardless of number of lesions)
- Can also be classified based on general clinical appearance
- Tuberculoid leprosy (TT) corresponds to paucibacillary
- Borderline tuberculoid leprosy (BT)
- Borderline leprosy (BB)
- Borerdline lepromatous leprosy (BL)
- Lepromatous leprosy (LL) corresponding to multibacillary disease
Type I reaction
- A cell-mediated hypersensitivity reaction that can develop in the course of treatment
- Also known as a reversal reaction due to the apparent worsening of the lesion
- Occurs most commonly in the borderline cases and may signal progression to the cell-mediated tuberculoid end of the clinical spectrum
Type 2 reaction
- A humorally-mediated hypersensitivity reaction that can develop in the course of treatment
- Also known as erythema nodosum leprosum
- Characterized by systemic illness and immune-complex deposition that appears as groups of tender subcutaneous nodules
- May have other signs of vasculitis, including fevers, arthralgias, neuralgia, lymphadenopathy, orchitis, and dactylitis
Management
Disease | Treatment |
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Paucibacillary | 6 months of rifampin, dapsone, and clofazimine |
Multibacillary | 12 months of rifampin, dapsone, and clofazimine |
Rifampin resistance | 6 months of at least two second-line drugs with clofazimine, followed by 18 months of one second-line drug with clofazimine |
Quinolone resistance | As for rifampin resistance, but without a fluoroquinolone |
Second-line antibiotics
References
- ^ boodman2021le