Leprosy is a chronic infectious disease caused by Mycobacterium leprae that primarily affects the skin and peripheral nervous system.
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name: Leprosy
creation_date: '2026-01-26T15:56:41Z'
updated_date: '2026-04-11T00:41:29Z'
category: Infectious Disease
description: >-
Leprosy is a chronic infectious disease caused by Mycobacterium leprae that
primarily affects the skin and peripheral nervous system.
disease_term:
term:
id: MONDO:0005124
label: leprosy
preferred_term: Leprosy
parents:
- Bacterial Infection
- Neglected tropical disease
infectious_agent:
- name: Mycobacterium leprae
infectious_agent_term:
preferred_term: Mycobacterium leprae
term:
id: NCBITaxon:1769
label: Mycobacterium leprae
description: Acid-fast bacterium that causes leprosy.
evidence:
- reference: PMID:28763601
reference_title: "Leprosy - an overview of clinical features, diagnosis, and treatment."
supports: SUPPORT
snippet: "Leprosy is a chronic infectious disease caused by Mycobacterium (M.) leprae."
explanation: The abstract identifies M. leprae as the causative agent.
transmission:
- name: Nasal droplet transmission
description: Likely transmitted via nasal droplet infection.
evidence:
- reference: PMID:28763601
reference_title: "Leprosy - an overview of clinical features, diagnosis, and treatment."
supports: SUPPORT
snippet: "While the exact route of transmission remains unknown, nasal droplet infection is thought to be most likely."
explanation: The abstract indicates nasal droplet infection as the most likely route.
pathophysiology:
- name: Skin and peripheral nerve involvement
description: The pathogen primarily affects skin and peripheral nerves.
evidence:
- reference: PMID:28763601
reference_title: "Leprosy - an overview of clinical features, diagnosis, and treatment."
supports: SUPPORT
snippet: "The pathogen primarily affects the skin and peripheral nervous system."
explanation: The abstract states primary involvement of skin and peripheral nerves.
- name: Peripheral nerve affinity
description: M. leprae shows affinity for peripheral nerves leading to neuropathy.
evidence:
- reference: PMID:11791665
reference_title: "Mycobacterium leprae and leprosy: a compendium."
supports: SUPPORT
snippet: "The bacteria have affinity to the peripheral nerves and are likely to cause neuropathy."
explanation: The abstract notes affinity for peripheral nerves and neuropathy.
- name: Enhanced Cell-Mediated Immunity in Type 1 Reaction
description: Aberrant upregulation of T cell-mediated immune responses against M. leprae antigens that initiates Type 1 (reversal) leprosy reactions.
cell_types:
- preferred_term: CD4-positive, alpha-beta T cell
term:
id: CL:0000624
label: CD4-positive, alpha-beta T cell
biological_processes:
- preferred_term: T cell mediated immunity
term:
id: GO:0002456
label: T cell mediated immunity
modifier: INCREASED
downstream:
- target: Type 1 Delayed-Type Hypersensitivity Response
description: Enhanced cell-mediated immunity drives a delayed-type (type IV) hypersensitivity response against persisting mycobacterial antigens.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 1 leprosy reaction is a delayed-type hypersensitivity response due to enhanced cell-mediated immunity"
explanation: The review attributes the delayed-type hypersensitivity response in Type 1 reactions directly to enhanced cell-mediated immunity.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 1 leprosy reaction is a delayed-type hypersensitivity response due to enhanced cell-mediated immunity"
explanation: The review identifies enhanced cell-mediated immunity as the initiating immunological event in Type 1 reactions.
- name: Type 1 Delayed-Type Hypersensitivity Response
description: Type IV (cell-mediated, delayed) hypersensitivity reaction against M. leprae antigens that produces acute inflammation in established leprosy lesions and peripheral nerves.
cell_types:
- preferred_term: CD4-positive, alpha-beta T cell
term:
id: CL:0000624
label: CD4-positive, alpha-beta T cell
biological_processes:
- preferred_term: Type IV hypersensitivity
term:
id: GO:0001806
label: type IV hypersensitivity
- preferred_term: Inflammatory response
term:
id: GO:0006954
label: inflammatory response
modifier: INCREASED
downstream:
- target: Localized skin lesion
description: Delayed-type hypersensitivity inflammation aggravates pre-existing leprosy skin lesions.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "leading to the aggravation of pre-existing skin lesions and neuritis"
explanation: The review states the DTH response leads directly to aggravation of pre-existing skin lesions.
- target: Peripheral neuropathy
description: Delayed-type hypersensitivity inflammation in and around peripheral nerves produces neuritis and worsens peripheral neuropathy.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "leading to the aggravation of pre-existing skin lesions and neuritis"
explanation: The review states the DTH response leads to neuritis, the inflammatory substrate of leprosy peripheral neuropathy.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 1 leprosy reaction is a delayed-type hypersensitivity response"
explanation: The review identifies Type 1 leprosy reaction as a delayed-type (type IV) hypersensitivity response.
- name: Immune-Complex Formation in Type 2 Reaction
description: Antigen-antibody (immune-complex) mediated type III hypersensitivity response to M. leprae antigens that drives Erythema Nodosum Leprosum and its systemic manifestations.
biological_processes:
- preferred_term: Type III hypersensitivity
term:
id: GO:0001802
label: type III hypersensitivity
- preferred_term: Inflammatory response
term:
id: GO:0006954
label: inflammatory response
modifier: INCREASED
downstream:
- target: Erythema nodosum leprosum
description: Immune-complex deposition in skin and subcutaneous tissues produces the reddish subcutaneous nodules of ENL together with systemic symptoms.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 2 reaction is an immune-complex mediated phenomenon associated with systemic symptoms along with the fresh appearance of reddish subcutaneous nodules."
explanation: The review attributes the appearance of ENL nodules and systemic symptoms directly to the immune-complex mediated mechanism.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 2 reaction is an immune-complex mediated phenomenon"
explanation: The review identifies Type 2 leprosy reaction as an immune-complex (type III hypersensitivity) mediated phenomenon.
- name: Endothelial Cell Injury in Lucio Phenomenon
description: Direct injury and apoptosis of small-vessel endothelial cells in the skin that underlies the vascular pathology of the Lucio phenomenon (Type 3 leprosy reaction).
cell_types:
- preferred_term: endothelial cell
term:
id: CL:0000115
label: endothelial cell
biological_processes:
- preferred_term: Endothelial cell apoptotic process
term:
id: GO:0072577
label: endothelial cell apoptotic process
modifier: INCREASED
downstream:
- target: Cutaneous Vascular Necrosis in Lucio Phenomenon
description: Endothelial injury leads to occlusive vasculopathy and ischemic necrosis of overlying cutaneous tissue.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Lucio phenomenon, which is due to endothelial cell injury, usually presents with tender purpura on the extremities which becomes necrotic and ulcerated."
explanation: The review attributes the necrotic and ulcerated cutaneous lesions of the Lucio phenomenon to endothelial cell injury.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Lucio phenomenon, which is due to endothelial cell injury"
explanation: The review identifies endothelial cell injury as the primary mechanism underlying the Lucio phenomenon.
- name: Cutaneous Vascular Necrosis in Lucio Phenomenon
description: Ischemic necrosis and ulceration of skin secondary to endothelial injury and small-vessel occlusion in the Lucio phenomenon, manifesting as tender purpura on the extremities that becomes necrotic and ulcerated.
cell_types:
- preferred_term: endothelial cell
term:
id: CL:0000115
label: endothelial cell
biological_processes:
- preferred_term: Inflammatory response
term:
id: GO:0006954
label: inflammatory response
modifier: INCREASED
downstream:
- target: Purpura with tissue necrosis
description: Cutaneous vascular injury manifests as tender purpura on the extremities that progresses to necrosis and ulceration.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "tender purpura on the extremities which becomes necrotic and ulcerated"
explanation: The review describes the clinical manifestation of cutaneous vascular necrosis in the Lucio phenomenon as tender purpura that becomes necrotic and ulcerated.
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "presents with tender purpura on the extremities which becomes necrotic and ulcerated"
explanation: The review describes the cutaneous vascular necrosis that develops in the Lucio phenomenon.
phenotypes:
- name: Peripheral neuropathy
category: Neurologic
frequency: COMMON
phenotype_term:
preferred_term: Peripheral neuropathy
term:
id: HP:0009830
label: Peripheral neuropathy
evidence:
- reference: PMID:11791665
reference_title: "Mycobacterium leprae and leprosy: a compendium."
supports: SUPPORT
snippet: "The bacteria have affinity to the peripheral nerves and are likely to cause neuropathy."
explanation: The abstract links leprosy to neuropathy.
- name: Localized skin lesion
category: Dermatologic
frequency: COMMON
phenotype_term:
preferred_term: Localized skin lesion
term:
id: HP:0011355
label: Localized skin lesion
evidence:
- reference: PMID:28763601
reference_title: "Leprosy - an overview of clinical features, diagnosis, and treatment."
supports: SUPPORT
snippet: "Apart from the various characteristic skin lesions, the condition is marked by damage to the peripheral nervous system."
explanation: The abstract notes characteristic skin lesions in leprosy.
- name: Erythema nodosum leprosum
category: Dermatologic
frequency: OCCASIONAL
description: Acute immune-complex mediated inflammatory manifestation of leprosy presenting with reddish nodules and systemic symptoms, characteristic of Type 2 leprosy reactions.
phenotype_term:
preferred_term: Erythema nodosum
term:
id: HP:0012219
label: Erythema nodosum
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Type 2 reaction is an immune-complex mediated phenomenon associated with systemic symptoms along with the fresh appearance of reddish subcutaneous nodules."
explanation: The review documents the appearance of reddish nodules in Type 2 leprosy reactions (Erythema Nodosum Leprosum).
- name: Purpura with tissue necrosis
category: Dermatologic
frequency: RARE
description: Severe vascular manifestation of Lucio phenomenon characterized by endothelial cell injury presenting as tender purpura that progresses to necrosis and ulceration, primarily on extremities.
phenotype_term:
preferred_term: Purpura
term:
id: HP:0000979
label: Purpura
evidence:
- reference: PMID:42157916
reference_title: "Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches-A Narrative Review"
supports: SUPPORT
snippet: "Lucio phenomenon, which is due to endothelial cell injury, usually presents with tender purpura on the extremities which becomes necrotic and ulcerated."
explanation: The review describes purpura and necrotic ulceration as characteristic manifestations of Lucio phenomenon.
treatments:
- name: Multidrug therapy with rifampicin, dapsone, and clofazimine
description: Multidrug therapy includes rifampicin, dapsone, and clofazimine for multibacillary disease.
treatment_term:
preferred_term: Pharmacotherapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: rifampicin
term:
id: CHEBI:28077
label: rifampicin
- preferred_term: clofazimine
term:
id: CHEBI:3749
label: clofazimine
evidence:
- reference: PMID:28763601
reference_title: "Leprosy - an overview of clinical features, diagnosis, and treatment."
supports: SUPPORT
snippet: "While paucibacillary forms are treated with rifampicin and dapsone for at least six months, multibacillary leprosy is treated for at least twelve months, additionally requiring clofazimine."
explanation: The abstract describes multidrug therapy regimens.
- name: Corticosteroid therapy for Type 1 reaction
description: Corticosteroids, particularly prednisone, are used to suppress the delayed-type hypersensitivity response in Type 1 (reversal) leprosy reactions, typically administered over 6 months or less.
treatment_term:
preferred_term: corticosteroid therapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: prednisone
term:
id: CHEBI:8382
label: prednisone
target_mechanisms:
- target: Type 1 Delayed-Type Hypersensitivity Response
description: Corticosteroids suppress the cell-mediated immune response and delayed-type hypersensitivity that drives Type 1 reaction.
evidence:
- reference: PMID:30226355
reference_title: "Corticosteroid therapy in borderline tuberculoid leprosy patients co-infected with HIV undergoing reversal reaction: a clinical study."
supports: SUPPORT
snippet: "Variables were analysed during and after multidrug therapy between the first and last days of prednisone, which occurred up to a maximum of 6 months after initiating corticosteroid therapy."
explanation: The study documents prednisone use for treating reversal reactions in leprosy patients, with treatment durations up to 6 months.
- name: Thalidomide therapy for Type 2 reaction (ENL)
description: Thalidomide is the most effective agent for treating Type 2 leprosy reactions (Erythema Nodosum Leprosum), either as monotherapy or in combination with corticosteroids. It acts as a TNF-alpha inhibitor and prevents recurrence of ENL.
treatment_term:
preferred_term: thalidomide therapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: thalidomide
term:
id: CHEBI:9513
label: thalidomide
target_mechanisms:
- target: Immune-Complex Formation in Type 2 Reaction
description: Thalidomide inhibits TNF-alpha and modulates the immune-complex mediated response in ENL.
evidence:
- reference: PMID:12680478
reference_title: "Thalidomide for erythema nodosum leprosum and other applications."
supports: SUPPORT
snippet: "Thalidomide, an inhibitor of tumor necrosis factor a, is the best known agent for short-term treatment of ENL skin manifestations, as well as postremission maintenance therapy to prevent recurrence. For this indication, it is effective as monotherapy and as part of combination therapy with corticosteroids."
explanation: The review identifies thalidomide as the primary treatment for ENL, effective either alone or combined with corticosteroids, with proven ability to prevent recurrence.
- reference: PMID:33035210
reference_title: "Thalidomide in the treatment of erythema nodosum leprosum (ENL) in an outpatient setting: A five-year retrospective analysis from a leprosy referral centre in India."
supports: SUPPORT
snippet: "Management of ENL requires high doses of oral corticosteroids, which may not be universally effective and pose serious adverse effects. Thalidomide has proven to be a steroid-sparing agent and is useful in controlling the reactions."
explanation: The study confirms thalidomide's role as a steroid-sparing alternative in ENL management, allowing reduction of corticosteroid doses while controlling reactions.
- name: Thalidomide and multidrug therapy for Lucio phenomenon
description: Thalidomide combined with multidrug therapy is used to manage Lucio phenomenon, the most severe leprosy reaction characterized by necrotizing vascular lesions. Aggressive antimicrobial therapy and thalidomide provide better control of type 3 reactions.
treatment_term:
preferred_term: combination thalidomide and multidrug therapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: thalidomide
term:
id: CHEBI:9513
label: thalidomide
- preferred_term: rifampicin
term:
id: CHEBI:28077
label: rifampicin
- preferred_term: clofazimine
term:
id: CHEBI:3749
label: clofazimine
target_mechanisms:
- target: Endothelial Cell Injury in Lucio Phenomenon
description: Thalidomide combined with multidrug therapy suppresses endothelial cell injury and the vascular pathology of Lucio phenomenon.
evidence:
- reference: PMID:25432812
reference_title: "Lucio's leprosy: a clinical and therapeutic challenge."
supports: SUPPORT
snippet: "Fortunately, reaction episodes have decreased with the use of multidrug therapy, and better control of the type 2 reactions has been managed with the use of thalidomide, as in Lucio's phenomenon."
explanation: The review indicates that multidrug therapy combined with thalidomide improves control of Lucio phenomenon, the most severe form of leprosy reaction.
references:
- reference: DOI:10.1097/md.0000000000039006
title: 'An update of the diagnosis, treatment, and prevention of leprosy: A narrative review'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy is an infectious disease that remains a public health concern.
supporting_text: Leprosy is an infectious disease that remains a public health concern.
evidence:
- reference: DOI:10.1097/md.0000000000039006
reference_title: 'An update of the diagnosis, treatment, and prevention of leprosy: A narrative review'
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Leprosy is an infectious disease that remains a public health concern.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1186/s12879-023-08290-0
title: 'Protocol, rationale and design of BE-PEOPLE (Bedaquiline enhanced exposure prophylaxis for LEprosy in the Comoros): a cluster randomized trial on effectiveness of rifampicin and bedaquiline as post-exposure prophylaxis of leprosy contacts'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy is an ancient infectious disease with an annual global incidence of around 200,000 over the past decade.
supporting_text: Leprosy is an ancient infectious disease with an annual global incidence of around 200,000 over the past decade.
evidence:
- reference: DOI:10.1186/s12879-023-08290-0
reference_title: 'Protocol, rationale and design of BE-PEOPLE (Bedaquiline enhanced exposure prophylaxis for LEprosy in the Comoros): a cluster randomized trial on effectiveness of rifampicin and bedaquiline as post-exposure prophylaxis of leprosy contacts'
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Leprosy is an ancient infectious disease with an annual global incidence of around 200,000 over the past decade.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1186/s12879-024-09125-2
title: 'The PEP++ study protocol: a cluster-randomised controlled trial on the effectiveness of an enhanced regimen of post-exposure prophylaxis for close contacts of persons affected by leprosy to prevent disease transmission'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy is an infectious disease with a slow decline in global annual caseload in the past two decades.
supporting_text: Leprosy is an infectious disease with a slow decline in global annual caseload in the past two decades.
evidence:
- reference: DOI:10.1186/s12879-024-09125-2
reference_title: 'The PEP++ study protocol: a cluster-randomised controlled trial on the effectiveness of an enhanced regimen of post-exposure prophylaxis for close contacts of persons affected by leprosy to prevent disease transmission'
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Leprosy is an infectious disease with a slow decline in global annual caseload in the past two decades.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1186/s12879-024-09492-w
title: Any resurgence of leprosy cases in the Togo’s post-elimination period? Trend analysis of reported leprosy cases from 2010 to 2022
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy, or Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae.
supporting_text: Leprosy, or Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae.
evidence:
- reference: DOI:10.1186/s12879-024-09492-w
reference_title: Any resurgence of leprosy cases in the Togo’s post-elimination period? Trend analysis of reported leprosy cases from 2010 to 2022
supports: SUPPORT
evidence_source: OTHER
snippet: Leprosy, or Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1186/s12879-024-09937-2
title: Role of histopathological, serological and molecular findings for the early diagnosis of treatment failure in leprosy
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Role of histopathological, serological and molecular findings for the early diagnosis of treatment failure in leprosy
supporting_text: Role of histopathological, serological and molecular findings for the early diagnosis of treatment failure in leprosy
- reference: DOI:10.1371/journal.pmed.1004453
title: 'Safety of single-dose bedaquiline combined with rifampicin for leprosy post-exposure prophylaxis: A Phase 2 randomized non-inferiority trial in the Comoros Islands'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: To reduce leprosy risk in contacts of patients with leprosy by around 50%, the World Health Organization (WHO) recommends leprosy post-exposure prophylaxis (PEP) using single-dose rifampicin (SDR).
supporting_text: To reduce leprosy risk in contacts of patients with leprosy by around 50%, the World Health Organization (WHO) recommends leprosy post-exposure prophylaxis (PEP) using single-dose rifampicin (SDR).
evidence:
- reference: DOI:10.1371/journal.pmed.1004453
reference_title: 'Safety of single-dose bedaquiline combined with rifampicin for leprosy post-exposure prophylaxis: A Phase 2 randomized non-inferiority trial in the Comoros Islands'
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: To reduce leprosy risk in contacts of patients with leprosy by around 50%, the World Health Organization (WHO) recommends leprosy post-exposure prophylaxis (PEP) using single-dose rifampicin (SDR).
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1371/journal.pntd.0012446
title: Effectiveness of ongoing single dose rifampicin post-exposure prophylaxis (SDR-PEP) implementation under routine programme conditions—An observational study in Nepal
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy control remains a challenge in Nepal.
supporting_text: Leprosy control remains a challenge in Nepal.
evidence:
- reference: DOI:10.1371/journal.pntd.0012446
reference_title: Effectiveness of ongoing single dose rifampicin post-exposure prophylaxis (SDR-PEP) implementation under routine programme conditions—An observational study in Nepal
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Leprosy control remains a challenge in Nepal.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1371/journal.pone.0302753
title: 'Identification of potential biomarkers of leprosy: A study based on GEO datasets'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy has a high rate of cripplehood and lacks available early effective diagnosis methods for prevention and treatment, thus novel effective molecule markers are urgently required.
supporting_text: Leprosy has a high rate of cripplehood and lacks available early effective diagnosis methods for prevention and treatment, thus novel effective molecule markers are urgently required.
evidence:
- reference: DOI:10.1371/journal.pone.0302753
reference_title: 'Identification of potential biomarkers of leprosy: A study based on GEO datasets'
supports: SUPPORT
evidence_source: OTHER
snippet: Leprosy has a high rate of cripplehood and lacks available early effective diagnosis methods for prevention and treatment, thus novel effective molecule markers are urgently required.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.1590/0102-311xen038723
title: A cost-effectiveness analysis of a novel algorithm to sequentially diagnose leprosy based on manufactured tests under the SUS perspective
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: 'Brazil has the second largest number of leprosy cases (a disease with a significant burden) in the world.'
supporting_text: 'Brazil has the second largest number of leprosy cases (a disease with a significant burden) in the world.'
evidence:
- reference: DOI:10.1590/0102-311xen038723
reference_title: A cost-effectiveness analysis of a novel algorithm to sequentially diagnose leprosy based on manufactured tests under the SUS perspective
supports: SUPPORT
evidence_source: OTHER
snippet: 'Brazil has the second largest number of leprosy cases (a disease with a significant burden) in the world.'
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.3389/fimmu.2024.1298749
title: 'Leprosy: treatment, prevention, immune response and gene function'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Since the leprosy cases have fallen dramatically, the incidence of leprosy has remained stable over the past years, indicating that multidrug therapy seems unable to eradicate leprosy.
supporting_text: Since the leprosy cases have fallen dramatically, the incidence of leprosy has remained stable over the past years, indicating that multidrug therapy seems unable to eradicate leprosy.
evidence:
- reference: DOI:10.3389/fimmu.2024.1298749
reference_title: 'Leprosy: treatment, prevention, immune response and gene function'
supports: SUPPORT
evidence_source: OTHER
snippet: Since the leprosy cases have fallen dramatically, the incidence of leprosy has remained stable over the past years, indicating that multidrug therapy seems unable to eradicate leprosy.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.3389/fimmu.2024.1368460
title: 'Neutrophilic leukocytosis and erythema nodosum leprosum in leprosy: insights from a retrospective observational study'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy reactions represent immunologically mediated episodes of acute inflammation that, if not diagnosed and treated promptly, can cause irreversible impairment of nerve function and permanent disabilities.
supporting_text: Leprosy reactions represent immunologically mediated episodes of acute inflammation that, if not diagnosed and treated promptly, can cause irreversible impairment of nerve function and permanent disabilities.
evidence:
- reference: DOI:10.3389/fimmu.2024.1368460
reference_title: 'Neutrophilic leukocytosis and erythema nodosum leprosum in leprosy: insights from a retrospective observational study'
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Leprosy reactions represent immunologically mediated episodes of acute inflammation that, if not diagnosed and treated promptly, can cause irreversible impairment of nerve function and permanent disabilities.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.3389/fimmu.2024.1416177
title: 'An update on leprosy immunopathogenesis: systematic review'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy is a chronic infectious condition and the main cause of neuropathy that occurs brought on by M. leprae.
supporting_text: Leprosy is a chronic infectious condition and the main cause of neuropathy that occurs brought on by M. leprae.
evidence:
- reference: DOI:10.3389/fimmu.2024.1416177
reference_title: 'An update on leprosy immunopathogenesis: systematic review'
supports: SUPPORT
evidence_source: OTHER
snippet: Leprosy is a chronic infectious condition and the main cause of neuropathy that occurs brought on by M. leprae.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.3389/fphar.2024.1361641
title: 'Leprosy: Comprehensive insights into pathology, immunology, and cutting-edge treatment strategies, integrating nanoparticles and ethnomedicinal plants'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Mycobacterium leprae is the causative agent responsible for the chronic disease known as leprosy.
supporting_text: Mycobacterium leprae is the causative agent responsible for the chronic disease known as leprosy.
evidence:
- reference: DOI:10.3389/fphar.2024.1361641
reference_title: 'Leprosy: Comprehensive insights into pathology, immunology, and cutting-edge treatment strategies, integrating nanoparticles and ethnomedicinal plants'
supports: SUPPORT
evidence_source: OTHER
snippet: Mycobacterium leprae is the causative agent responsible for the chronic disease known as leprosy.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.3389/fphar.2024.1399363
title: 'Adenosine A2A receptor as a potential regulator of Mycobacterium leprae survival mechanisms: new insights into leprosy neural damage'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Leprosy is a chronic infectious disease caused by Mycobacterium leprae, which can lead to a disabling neurodegenerative condition.
supporting_text: Leprosy is a chronic infectious disease caused by Mycobacterium leprae, which can lead to a disabling neurodegenerative condition.
evidence:
- reference: DOI:10.3389/fphar.2024.1399363
reference_title: 'Adenosine A2A receptor as a potential regulator of Mycobacterium leprae survival mechanisms: new insights into leprosy neural damage'
supports: SUPPORT
evidence_source: OTHER
snippet: Leprosy is a chronic infectious disease caused by Mycobacterium leprae, which can lead to a disabling neurodegenerative condition.
explanation: Deep research cited this publication as relevant literature for Leprosy.
- reference: DOI:10.47276/lr.95.1.7
title: 'The epidemiology of leprosy in Karonga District, northern Malawi 1973–2023: An analysis of leprosy’s distribution, risk factors, control and decline in rural Africa'
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: 'The epidemiology of leprosy in Karonga District, northern Malawi 1973–2023: An analysis of leprosy’s distribution, risk factors, control and decline in rural Africa'
supporting_text: 'The epidemiology of leprosy in Karonga District, northern Malawi 1973–2023: An analysis of leprosy’s distribution, risk factors, control and decline in rural Africa'
- reference: DOI:10.47276/lr.95.2.2024018
title: Is the WHO ‘global’ rate indicator an accurate reflection of the annual leprosy-associated disability burden experienced worldwide?
found_in:
- Leprosy-deep-research-falcon.md
findings:
- statement: Is the WHO ‘global’ rate indicator an accurate reflection of the annual leprosy-associated disability burden experienced worldwide?
supporting_text: Is the WHO ‘global’ rate indicator an accurate reflection of the annual leprosy-associated disability burden experienced worldwide?
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.
Please provide a comprehensive research report on Leprosy covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.
For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.
Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed
Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Search first: CTD, PubMed, PheGenI, GxE databases
Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC
For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities
For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype
Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser
Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Search first: CDC databases, WHO, PubMed, NHANES
Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON
Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Search first: PubMed, Gene Ontology, Reactome
Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types
Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Search first: OMIM, Orphanet, HPO, PubMed
Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.
Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Search first: NSGC resources, ACMG guidelines, GeneReviews
Search first: Clinical guidelines, FDA approvals, PubMed
Search first: NCBI Taxonomy
Search first: VBO (Vertebrate Breed Ontology)
Search first: NCBI Gene
Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease
This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details
Leprosy is a chronic infectious disease caused mainly by Mycobacterium leprae (and in some settings M. lepromatosis), characterized by skin lesions and peripheral neuropathy that can progress to permanent disability. Despite major reductions after WHO-recommended multidrug therapy (MDT), global transmission continues, with ~174,087 new cases reported in 2022 (21.8 per million) and a persistent burden of grade-2 disability (G2D) at diagnosis, reflecting delayed detection in many settings. Recent (2023–2024) work emphasizes (i) host-directed mechanisms of nerve injury centered on Schwann cell infection and lipid metabolic reprogramming, (ii) improved diagnostic/monitoring strategies combining histopathology, serology and molecular tests, and (iii) intensified prevention via post-exposure prophylaxis (PEP), including evaluation of strengthened antimicrobial regimens beyond single-dose rifampicin. (bakoubayi2024anyresurgenceof pages 1-2, li2024leprosytreatmentprevention pages 5-6, dornelas2024roleofhistopathological pages 1-2, jong2024safetyofsingledose pages 1-2)
Leprosy (Hansen’s disease) is an infectious disease that primarily affects skin and peripheral nerves, potentially causing long-term disability and stigma. A recent narrative review states: “Leprosy is an infectious disease that remains a public health concern… [and] primarily affects the skin and peripheral nerves, potentially leading to long-term disability and stigma.” (Medicine; Aug 2024; https://doi.org/10.1097/md.0000000000039006) (huang2024anupdateof pages 1-2)
Key microbiologic features summarized in recent reviews include slow growth, prolonged incubation, and a temperature preference consistent with predilection for cooler body sites and peripheral nerves. (huang2024anupdateof pages 1-2)
Most information used here is aggregated from disease-level resources and peer-reviewed literature (narrative/systematic reviews, epidemiological studies, clinical trials), rather than individual EHR-derived case data. (huang2024anupdateof pages 1-2, silva2024anupdateon pages 1-2, bakoubayi2024anyresurgenceof pages 1-2)
Recent synthesis notes long incubation (often years) and supports person-to-person spread, especially from untreated individuals with high bacillary load. (huang2024anupdateof pages 1-2, kimta2024leprosycomprehensiveinsights pages 1-2)
Host genetic susceptibility (polygenic): A 2024 review emphasizes that “the infection and pathogenesis largely depend on the host’s genetic background and immunity,” and notes “more than 30 susceptibility genes” have been implicated. (Frontiers in Immunology; Feb 2024; https://doi.org/10.3389/fimmu.2024.1298749) (li2024leprosytreatmentprevention pages 1-2)
Contact-related risk: Household contacts (and other close contacts) are repeatedly identified as high risk and are the target population for PEP strategies. (li2024leprosytreatmentprevention pages 1-2, hinders2024thepep++study pages 1-2)
Direct protective-factor quantification was not retrieved in the current evidence set. However, immunoprophylaxis approaches (BCG and candidate vaccines such as LepVax/MiP) are discussed as prevention tools; effectiveness varies and is still under development. (li2024leprosytreatmentprevention pages 1-2, slater2023acurrentperspective pages 45-47)
A specific, quantitatively supported gene–environment interaction model was not retrieved in the current evidence set. The most consistent “interaction” framing supported here is that genetic background shapes immune polarization and susceptibility, while exposure intensity/duration (e.g., household contact) determines infection risk. (li2024leprosytreatmentprevention pages 1-2, hinders2024thepep++study pages 1-2)
The WHO clinical diagnostic triad (also useful as phenotype anchors) includes: 1) Hypopigmented or reddish skin lesions with sensory loss (HPO suggestions: HP:0001010 Hypopigmentation; HP:0000989 Skin rash; HP:0000762 Hypoesthesia). (huang2024anupdateof pages 6-6) 2) Thickened/enlarged peripheral nerves with sensory/motor loss (HPO suggestions: HP:0009830 Peripheral neuropathy; HP:0001288 Abnormality of peripheral nerve conduction; HP:0003390 Nerve hypertrophy). (huang2024anupdateof pages 6-6) 3) Acid-fast bacilli (AFB) demonstrable in slit-skin smear or biopsy (maps more to lab findings than HPO). (huang2024anupdateof pages 6-6)
Leprosy reactions are acute inflammatory episodes that accelerate nerve injury and disability. * Type 2 reaction / Erythema nodosum leprosum (ENL): In a 2024 Brazilian BL/LL cohort (n=146), reactions were common (85%) and ENL comprised 65% of reactional episodes; 55% of ENL patients had >2 episodes (mean 2.6). (Frontiers in Immunology; Jul 2024; https://doi.org/10.3389/fimmu.2024.1368460) (barboza2024neutrophilicleukocytosisand pages 1-2) * HPO suggestions: HP:0000994 Erythema nodosum; HP:0011123 Fever (often associated); HP:0000988 Skin ulcer (severe forms).
ENL is associated with neutrophilia in the 2024 cohort: * Median neutrophils higher in those developing ENL (4,567 vs 3,731 cells/mm³) * Severity gradient: 6,066 (mild) vs 10,243 (moderate/severe) cells/mm³ * Longitudinal within-person: BL/LL 4,896 vs ENL 8,408 cells/mm³ (p<0.0001) (barboza2024neutrophilicleukocytosisand pages 1-2)
Quantitative QoL instruments (e.g., DLQI, SF-36, EQ-5D) were not retrieved in the current evidence set, but recent reviews emphasize persistent neuropathy and disability even after MDT, which is a major driver of QoL impairment. (huang2024anupdateof pages 1-2)
Leprosy is not a monogenic disorder; instead it shows polygenic susceptibility with immune-related loci. The retrieved evidence supports the concept of multiple susceptibility genes (>30) rather than specific pathogenic variants with ACMG classifications. (li2024leprosytreatmentprevention pages 1-2)
A 2024 antimicrobial resistance review (retrieved but not deeply evidenced here) is complemented by a 2024 prevention/treatment review noting concern about “the emergence of rifampicin-resistant strains.” (li2024leprosytreatmentprevention pages 1-2)
Not retrieved in this evidence set.
Not retrieved in this evidence set with quantitative support.
Causal pathogens: M. leprae and M. lepromatosis. (silva2024anupdateon pages 1-2, barboza2024neutrophilicleukocytosisand pages 1-2)
1) Exposure and infection → bacilli establish infection in cooler tissues. 2) Cell tropism: Primary infected cells include Schwann cells (peripheral glia) and dermal macrophages/histiocytes. (silva2024anupdateon pages 1-2, santos2024adenosinea2areceptor pages 1-2) 3) Schwann cell entry/internalization: A 2024 review describes binding of M. leprae to laminin-2/α-dystroglycan on the Schwann cell basal lamina with downstream PI3K signaling mediating internalization. (li2024leprosytreatmentprevention pages 5-6) 4) Immune-metabolic reprogramming: Infection promotes “foamy” lipid-laden cells and metabolic states favorable for persistence, including lipid droplet accumulation and cholesterol dependence. (santos2024adenosinea2areceptor pages 1-2, li2024leprosytreatmentprevention pages 5-6) 5) Immune polarization and antigen presentation defects: PGL-1-related suppression of MHC release and PRR-driven macrophage polarization shape Th/CD8 responses and clinical spectrum; adaptive immunity can exacerbate nerve injury. (silva2024anupdateon pages 1-2) 6) Clinical outcomes: Peripheral neuropathy, sensory/motor loss, deformities; reactional episodes (e.g., ENL) drive acute inflammation and irreversible nerve damage if untreated. (barboza2024neutrophilicleukocytosisand pages 1-2, silva2024anupdateon pages 1-2)
A 2024 primary study emphasizes that M. leprae infection “subvert[s]” host lipid metabolism to generate cholesterol-rich lipid droplets important for bacterial survival in Schwann cells, and reports a host-directed candidate pathway: adenosine A2A receptor signaling. Infected Schwann cells showed altered ectonucleotidase signaling (CD73/ADA up; A2AR down), while pharmacologic A2AR activation reduced lipid droplets, reduced IL-6/IL-8, and reduced intracellular M. leprae viability. (Frontiers in Pharmacology; Jun 2024; https://doi.org/10.3389/fphar.2024.1399363) (santos2024adenosinea2areceptor pages 1-2)
Ontology suggestions * GO biological processes: cholesterol metabolic process, lipid droplet organization, innate immune response, antigen processing and presentation, inflammatory response (santos2024adenosinea2areceptor pages 1-2, silva2024anupdateon pages 1-2) * Cell Ontology (CL) targets: Schwann cell (CL:0000218), macrophage (CL:0000235), dendritic cell (CL:0000451), CD8-positive T cell (CL:0000625)
UBERON suggestions * UBERON:0002097 (skin) * UBERON:0000010 (peripheral nervous system)
A WHO-derived global estimate reported in an epidemiologic analysis indicates 174,087 new cases in 2022, with a detection rate of 21.8 per million, and an increase relative to 2021 (noting COVID-era detection disruption). (bakoubayi2024anyresurgenceof pages 1-2)
Regional distribution (WHO-derived): Southeast Asia 66.5% of new cases; Africa 15.1%. (bakoubayi2024anyresurgenceof pages 1-2)
A 2024 analysis of WHO Weekly Epidemiological Record (WER) data reports that global new case counts declined from 407,791 (2004) to 174,087 (2022) while disability indicators show more complex patterns; notably, the G2D rate decreased from 2.9 per million (2004) to 1.2 per million (2022) but the proportion of new cases with G2D increased over time, consistent with later detection among those still being diagnosed. (quilter2024isthewho pages 3-6)
WHO has set G2D-rate milestones toward a 2030 target, reported as 0.92 per million (2023), 0.68 (2025), and 0.12 (2030). (quilter2024isthewho pages 6-9)
WHO clinical diagnosis is anchored in three cardinal signs: anesthetic skin lesions, peripheral nerve thickening with neurologic deficits, and AFB detection in slit-skin smear/biopsy. (huang2024anupdateof pages 6-6)
SSS is highly specific (~100%) but insensitive (commonly 18–30%), so a negative SSS does not exclude disease. (huang2024anupdateof pages 6-6, huang2024anupdateof pages 6-7)
Biopsy with Fite-Faraco/modified Ziehl–Neelsen staining and histologic bacillary index supports confirmation and classification, but inter-observer variability exists in routine practice, as illustrated in the long-running Karonga (Malawi) program with thousands of biopsies and harmonization efforts. (team2024theepidemiologyof pages 11-14)
PCR/qPCR can substantially increase sensitivity, especially in early/low-bacillary-load disease and for contacts, but implementation is constrained by cost and infrastructure. PCR sensitivity is much higher in BI-positive/lepromatous disease (87–100%) than in BI-negative/tuberculoid forms (30–83%) in reported studies summarized by a 2024 narrative review. (huang2024anupdateof pages 6-6)
A 2023 perspective notes that “PCR as a diagnostic tool is one of the most reliable and robust techniques,” and highlights ongoing needs for assay standardization and cost-effective deployment. (slater2023acurrentperspective pages 45-47)
Anti–PGL-I IgM serology is used as a relatively simple surrogate of bacterial load and is helpful for MB vs PB classification, but has limited utility for PB detection. (huang2024anupdateof pages 6-6)
Treatment failure monitoring (2024 primary study): A case-control study (BMC Infectious Diseases; Oct 2024; https://doi.org/10.1186/s12879-024-09937-2) found that foamy granulomas (OR 7.36), histologic bacillary index thresholds (AUC ~0.75), anti-PGL-I ELISA index (AUC ~0.74), and real-time PCR positivity (3.43-fold increased odds) were associated with treatment failure; combined models predicted treatment failure with high estimated likelihood (up to ~95%). (dornelas2024roleofhistopathological pages 1-2)
Omics-derived candidate biomarkers (2024): A transcriptomic meta-analysis proposed immune-pathway hub genes (e.g., ITK, CD48, IL2RG, CCR5, JAK3, STAT1) as potential biomarkers requiring prospective validation. (zhou2024identificationofpotential pages 1-2)
A Brazilian SUS-perspective cost-effectiveness model evaluated a sequential diagnostic algorithm for household contacts (rapid IgM test → SSS → real-time PCR) versus SSS alone, reporting an incremental cost-effectiveness ratio of USD 616.46 per avoided undiagnosed case. (Cadernos de Saúde Pública; Jan 2024; https://doi.org/10.1590/0102-311xen038723) (costa2024acosteffectivenessanalysis pages 1-2)
Robust survival/mortality estimates were not retrieved in the current evidence set. The primary burden is morbidity from neuropathy and disability, with disability metrics (G2D rate/proportion) serving as key operational proxies for diagnostic timeliness and long-term outcomes. (quilter2024isthewho pages 3-6, quilter2024isthewho pages 6-9)
WHO MDT (introduced 1981; free access from 1995) is foundational, but recent reviews stress that “multidrug therapy seems unable to eradicate leprosy,” and that antimicrobial resistance (e.g., rifampicin resistance) threatens control. (li2024leprosytreatmentprevention pages 1-2, huang2024anupdateof pages 1-2)
MAXO suggestions * Antimicrobial drug therapy (MAXO:0000767)
Reactional episodes (including ENL) are major drivers of nerve injury. The retrieved evidence set includes recent cohort-level quantification of ENL recurrence and inflammatory correlates (neutrophilia) supporting intensive monitoring and timely anti-inflammatory treatment strategies. (barboza2024neutrophilicleukocytosisand pages 1-2)
MAXO suggestions * Anti-inflammatory therapy (MAXO:0000917) * Immunosuppressive therapy (MAXO:0000919)
Host-directed approaches: Recent mechanistic work implicates Schwann-cell lipid droplet metabolism and adenosinergic signaling (A2AR) as potential host-directed targets to reduce intracellular survival and inflammatory cytokines. (santos2024adenosinea2areceptor pages 1-2)
WHO recommends single-dose rifampicin PEP (SDR-PEP). A 2024 Phase 2 safety trial reiterates this standard and states SDR-PEP reduces leprosy risk in contacts “by around 50%” and cites the COLEP trial’s 57% incidence reduction over 2 years. (jong2024safetyofsingledose pages 1-2, younoussa2023protocolrationaleand pages 1-2)
Routine-program effectiveness (Nepal, 2024): Under program conditions, SDR-PEP was associated with a 72% reduction in risk among contacts (HR 0.28, 95% CI 0.18–0.44). (PLOS NTD; Dec 2024; https://doi.org/10.1371/journal.pntd.0012446) (banstola2024effectivenessofongoing pages 1-2)
Program audits (Kiribati, 2024): An SDR-PEP program audit reported coverage of 84.7% (retrospective cohort) and 88.1% (prospective cohort), with median time to administration of 220 days vs 120 days respectively, illustrating key implementation bottlenecks. (jong2024safetyofsingledose pages 1-2)
Because SDR-PEP effectiveness is variable across contexts, multiple strengthened regimens are in late-stage evaluation.
BE-PEOPLE (bedaquiline + rifampicin) trial program (BMC Infectious Diseases; May 2023): Designed to test enhanced PEP for contacts, explicitly building from COLEP’s 57% effect and addressing persistent transmission in Comoros. (https://doi.org/10.1186/s12879-023-08290-0; NCT05597280) (younoussa2023protocolrationaleand pages 1-2)
Phase 2 safety evidence for bedaquiline-enhanced PEP (PLOS Medicine; Oct 2024): A randomized non-inferiority safety trial (n=313; 99% completed) comparing bedaquiline 800 mg + rifampicin 600 mg vs rifampicin 600 mg alone found a small QTc difference (1.8 ms; 95% CI −1.8 to 5.3) and no QTc >450 ms or >50 ms increase, supporting feasibility of Phase 3 efficacy testing. (https://doi.org/10.1371/journal.pmed.1004453; NCT05406479) (jong2024safetyofsingledose pages 1-2, jong2024safetyofsingledose pages 7-9)
PEP++ trial (BMC Infectious Diseases; Feb 2024): Tests three monthly doses of rifampicin plus clarithromycin versus SDR-PEP to increase protection in the highest-risk contact groups. (https://doi.org/10.1186/s12879-024-09125-2) (hinders2024thepep++study pages 1-2)
No leprosy-specific licensed vaccine exists; BCG provides partial protection with wide variability across studies and settings, and candidates such as LepVax/MiP are in development. (slater2023acurrentperspective pages 45-47, li2024leprosytreatmentprevention pages 1-2)
Evidence on zoonotic reservoirs (e.g., armadillos/red squirrels) was not retrieved in the current evidence set.
A practical limitation emphasized in a 2023 perspective is that “The inability to culture M. leprae in vitro has also hampered investigations… Mouse foot pads have been the only feasible method to measure drug susceptibility,” making the mouse footpad model central for drug testing and resistance phenotyping. (slater2023acurrentperspective pages 45-47)
1) Disability indicator debate and program metrics (2024): Detailed analysis of WHO WER shows declining G2D rates but increasing G2D proportion, arguing for multi-metric monitoring to avoid masking worsening delayed diagnosis in high-burden settings. (quilter2024isthewho pages 3-6, quilter2024isthewho pages 6-9) 2) PEP intensification beyond SDR-PEP: 2024 observational program data show strong effectiveness under routine conditions (Nepal HR 0.28), while global trials are evaluating multidose/combination regimens (PEP++; BE-PEOPLE). (banstola2024effectivenessofongoing pages 1-2, hinders2024thepep++study pages 1-2, younoussa2023protocolrationaleand pages 1-2) 3) Safety de-risking for new prophylaxis regimens: Phase 2 randomized evidence supports cardiac/liver safety of single-dose bedaquiline + rifampicin PEP as a precursor to large Phase 3 efficacy trials. (jong2024safetyofsingledose pages 1-2) 4) Mechanistic host-directed targets in neuropathogenesis (2024): New Schwann-cell focused work highlights adenosinergic signaling (A2AR) and lipid droplet metabolism as intervention axes to reduce M. leprae viability and inflammatory cytokines. (santos2024adenosinea2areceptor pages 1-2) 5) Diagnostics moving toward integrated algorithms: Evidence supports combined histology/serology/PCR approaches to detect treatment failure and to operationalize earlier diagnosis in contacts, with explicit cost-effectiveness modelling in Brazil. (dornelas2024roleofhistopathological pages 1-2, costa2024acosteffectivenessanalysis pages 1-2)
| Descriptor | Numeric value(s) | Population / context | Year | Citation |
|---|---|---|---|---|
| Global new cases and detection rate | 174,087 new cases; 21.8 per million | WHO global leprosy reports | 2022 | (bakoubayi2024anyresurgenceof pages 1-2) |
| Global G2D rate trend | 2.9 per million (2004) → 1.2 per million (2022) | WHO WER global grade-2 disability rate | 2004 vs 2022 | (quilter2024isthewho pages 3-6) |
| WHO G2D milestone targets | 0.92 per million (2023); 0.68 (2025); 0.12 (2030) | WHO target trajectory for new G2D cases | 2023–2030 | (quilter2024isthewho pages 6-9) |
| Regional distribution of new cases | SEAR 66.5%; Africa 15.1% | Share of global new cases reported by WHO | 2022 | (bakoubayi2024anyresurgenceof pages 1-2) |
| WHO-reported leprosy reactions | Type 1: 15,031; Type 2: 6,296; only 42 countries reported | WHO global update; reaction reporting incomplete | 2022 data reported in 2023 update | (saunderson2023whogloballeprosy pages 1-2) |
| ENL cohort: sex, ENL frequency, recurrence | Male 75%; reactional episode 85%; ENL among reactions 65%; >2 ENL episodes in 55%; mean 2.6 episodes | 146 BL/LL patients in retrospective cohort, Brazil | 2024 study | (barboza2024neutrophilicleukocytosisand pages 1-2) |
| SDR-PEP effectiveness: COLEP | 57% reduction in incidence among contacts after 2 years | Household/close contacts; foundational evidence for WHO SDR-PEP recommendation | Prior trial, cited in 2023–2024 papers | (younoussa2023protocolrationaleand pages 1-2, hinders2024thepep++study pages 1-2) |
| SDR-PEP effectiveness: Nepal routine implementation | HR 0.28 (95% CI 0.18–0.44); ~72% risk reduction | Contacts in two Nepal districts under routine programme conditions | 2024 | (banstola2024effectivenessofongoing pages 1-2) |
| Enhanced PEP: double-dose rifampicin | 45% reduction in risk | Comoros and Madagascar trial background cited in BE-PEP paper | Prior trial, summarized 2024 | (jong2024safetyofsingledose pages 2-4) |
| BE-PEP safety (bedaquiline + rifampicin) | n=313 enrolled; 310/313 (99%) completed; QTc between-arm difference 1.8 ms (95% CI −1.8 to 5.3); no QTc >450 ms or increase >50 ms | Phase 2 randomized non-inferiority safety trial, Comoros | 2024 | (jong2024safetyofsingledose pages 1-2, jong2024safetyofsingledose pages 7-9) |
| Kiribati SDR coverage and timeliness | SDR coverage 84.7% retrospective, 88.1% prospective; median time to SDR 220 days (IQR 162–468) retrospective, 120 days (IQR 36–283) prospective | Household contacts in national SDR-PEP programme audit | 2018–2022 programme, 2024 report | (jong2024safetyofsingledose pages 1-2) |
Table: This table compiles key recent quantitative evidence on leprosy epidemiology, disability burden, reactions, prophylaxis effectiveness, and implementation metrics. It is useful as a compact evidence summary for a disease knowledge base or research report.
References
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