Rickettsialpox is an acute mite-borne rickettsiosis caused by the obligate intracellular Gram-negative bacterium Rickettsia akari. The house mouse mite inoculates the organism into skin, producing an eschar at the bite site followed by fever and a papulovesicular exanthem. Although R. akari has been reassigned from the spotted fever group to the transitional group on genomic grounds, the infection remains clinically tied to the spotted-fever rickettsioses through eschar-associated cutaneous disease, microvascular endothelial infection, and spotted-fever-group serologic cross-reactivity.
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name: Rickettsialpox
creation_date: "2026-09-25T11:47:36Z"
category: Infectious Disease
parents:
- Spotted fever rickettsiosis
- Rickettsial disease
synonyms:
- Rickettsia akari infection
description: >-
Rickettsialpox is an acute mite-borne rickettsiosis caused by the obligate
intracellular Gram-negative bacterium Rickettsia akari. The house mouse mite
inoculates the organism into skin, producing an eschar at the bite site followed
by fever and a papulovesicular exanthem. Although R. akari has been reassigned
from the spotted fever group to the transitional group on genomic grounds, the
infection remains clinically tied to the spotted-fever rickettsioses through
eschar-associated cutaneous disease, microvascular endothelial infection, and
spotted-fever-group serologic cross-reactivity.
disease_term:
preferred_term: rickettsialpox
term:
id: MONDO:0019360
label: rickettsialpox
references:
- reference: PMID:28846279
title: "Rickettsia akari (Rickettsialpox)."
tags:
- StatPearls
findings: []
- reference: PMID:18171106
title: Hepatitis in association with rickettsialpox.
found_in:
- Rickettsialpox-deep-research-openscientist.md
findings:
- statement: >-
Rickettsialpox is caused by Rickettsia akari, is transmitted by the house
mouse mite Liponyssoides sanguineus, and can rarely include self-limited
acute hepatitis.
supporting_text: >-
Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia
akari and transmitted by Liponyssoides sanguineus
- reference: PMID:14676069
title: >-
Increased detection of rickettsialpox in a New York City hospital following the
anthrax outbreak of 2001: use of immunohistochemistry for the rapid confirmation
of cases in an era of bioterrorism.
found_in:
- Rickettsialpox-deep-research-openscientist.md
findings:
- statement: >-
An 18-patient New York City case series supports rickettsialpox diagnosis
from eschar or papulovesicle skin-biopsy immunohistochemistry and paired
IgG serology.
supporting_text: >-
Immunohistochemical testing revealed spotted fever group rickettsiae in all
16 eschars and in 5 of the 9 papulovesicles tested.
- reference: PMID:2677080
title: Rickettsioses of the spotted fever group around the world.
found_in:
- Rickettsialpox-deep-research-openscientist.md
findings:
- statement: >-
The spotted-fever-group review includes rickettsialpox among SFG
rickettsioses, describes endothelial invasion with vascular permeability as
the shared lesion, and names doxycycline as empiric treatment.
supporting_text: >-
These obligate intracellular bacteria invade vascular endothelial cells,
which are damaged directly, causing increased vascular permeability.
classifications:
harrisons_chapter:
- classification_value: INFECTIOUS_DISEASES
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
quote_role: BACKGROUND
snippet: >-
Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia
akari and transmitted by Liponyssoides sanguineus
explanation: >-
Rickettsialpox is a bacterial rickettsiosis acquired from a mite vector,
placing it in Harrison's infectious diseases part.
definitions:
- name: Mite-borne Rickettsia akari disease
definition_type: OTHER
description: >-
Rickettsialpox is a mite-borne rickettsial infection caused by Rickettsia
akari, in which a vesicle at the bite site evolves to an eschar and is followed
by fever with a papular or vesicular rash.
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
quote_role: BACKGROUND
snippet: >-
Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia
akari and transmitted by Liponyssoides sanguineus
explanation: >-
Identifies the causal bacterium and the mite vector that define the disease.
infectious_agent:
- name: Rickettsia akari
infectious_agent_term:
preferred_term: Rickettsia akari
term:
id: NCBITaxon:786
label: Rickettsia akari
description: >-
The obligate intracellular rickettsial species that causes rickettsialpox.
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
quote_role: BACKGROUND
snippet: >-
Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia
akari and transmitted by Liponyssoides sanguineus
explanation: >-
Names R. akari as the causal bacterial species.
transmission:
- name: House mouse mite inoculation
description: >-
R. akari is transmitted from a rodent reservoir to people by the house mouse
mite Liponyssoides sanguineus rather than by ticks.
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
quote_role: BACKGROUND
snippet: >-
Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia
akari and transmitted by Liponyssoides sanguineus
explanation: >-
Names the vector that inoculates R. akari during a bite.
pathophysiology:
- name: Rickettsia akari Ribosomal Translation
description: >-
R. akari, like other bacteria, requires 70S-ribosome translation of its mRNA.
The bacterial ribosome is the conserved molecular target of tetracyclines,
which block aminoacyl-tRNA entry at the 30S subunit and arrest rickettsial
protein synthesis.
role: therapeutic_vulnerability
conforms_to: "bacterial_protein_synthesis_inhibition#Bacterial mRNA Translation by the Ribosome"
biological_processes:
- preferred_term: Translation
term:
id: GO:0006412
label: translation
evidence:
- reference: PMID:24336183
reference_title: "Ribosome-targeting antibiotics and mechanisms of bacterial resistance."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
The ribosome is one of the main antibiotic targets in the bacterial cell.
explanation: >-
The review establishes the bacterial ribosome as a principal antibiotic
target, the conserved process represented by this R. akari node.
- name: Obligate Intracellular Rickettsia akari Niche
description: >-
R. akari is an obligate intracellular Gram-negative bacterium. Its cytosolic
host-cell niche protects the organism from poorly cell-penetrant agents such
as beta-lactams, so effective antimicrobial therapy must use drugs that
accumulate inside eukaryotic cells.
role: intrinsic_resistance
conforms_to: "intracellular_pathogen_persistence#Intracellular Niche and Beta-Lactam Exclusion"
biological_processes:
- preferred_term: Biological Process Involved in Interaction with Host
term:
id: GO:0051701
label: biological process involved in interaction with host
evidence:
- reference: PMID:28846279
reference_title: Rickettsia akari (Rickettsialpox).
supports: SUPPORT
evidence_source: OTHER
snippet: >-
Like other rickettsiae in the genus, R. akari is an intracellular gram-negative
pathogen with features intermediate between viruses and bacteria.
explanation: >-
Identifies the causal species as an intracellular Gram-negative pathogen.
- reference: PMID:18611821
reference_title: "Intracellular organisms."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
The intracellular location of some microorganisms allow them to resist
antibiotics with poor ability to penetrate eukaryotic cell membranes, such as
the beta-lactam compounds.
explanation: >-
Establishes the shared pharmacologic consequence of an intracellular
bacterial niche.
- name: Cutaneous Rickettsia akari Infection
description: >-
After mite-bite inoculation, R. akari is present in the eschar and papular
skin lesions that define rickettsialpox. CD68-positive macrophages dominate
rickettsialpox skin lesions, making cutaneous mononuclear infection the
directly observed early tissue compartment in human disease.
cell_types:
- preferred_term: macrophage
term:
id: CL:0000235
label: macrophage
evidence:
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
IHC staining of biopsy specimens of eschars and papular lesions were positive for
spotted fever group rickettsiae for 32 patients.
explanation: >-
Skin-biopsy immunohistochemistry localizes rickettsial antigen in the
eschar and papular lesions of confirmed rickettsialpox cases.
- reference: PMID:30148688
reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
supports: SUPPORT
evidence_source: OTHER
quote_role: REVIEW_SYNTHESIS
snippet: >-
CD68+ macrophages are the predominant infected cells in the skin lesions of
patients with rickettsialpox.
explanation: >-
The review identifies the dominant infected cell type in rickettsialpox
skin lesions.
downstream:
- target: Inoculation Eschar Formation
causal_link_type: DIRECT
description: Local infection at the bite site produces an inoculation eschar.
- target: Endothelial Rickettsial Invasion and Vascular Leak
causal_link_type: DIRECT
description: >-
SFG rickettsiae spread from the inoculation site into vascular endothelial
cells and increase permeability.
- name: Endothelial Rickettsial Invasion and Vascular Leak
description: >-
R. akari was included among the SFG rickettsioses in a review that describes
vascular endothelial invasion, direct endothelial damage, and increased
vascular permeability as shared tissue events during systemic spread.
role: effector
biological_scale: CELLULAR
cell_types:
- preferred_term: vascular endothelial cell
term:
id: CL:0002139
label: endothelial cell of vascular tree
biological_processes:
- preferred_term: biological process involved in interaction with host
term:
id: GO:0051701
label: biological process involved in interaction with host
- preferred_term: positive regulation of vascular permeability
modifier: INCREASED
term:
id: GO:0043117
label: positive regulation of vascular permeability
evidence:
- reference: PMID:2677080
reference_title: Rickettsioses of the spotted fever group around the world.
supports: SUPPORT
evidence_source: OTHER
quote_role: REVIEW_SYNTHESIS
snippet: >-
These obligate intracellular bacteria invade vascular endothelial cells, which
are damaged directly, causing increased vascular permeability.
explanation: >-
The review names rickettsialpox among SFG rickettsioses before describing
endothelial invasion and vascular leak as the shared SFG lesion.
downstream:
- target: Small-Vessel Vasculitis
causal_link_type: DIRECT
description: Endothelial infection and leak progress into vasculitic tissue injury.
- target: Rare Hepatic Involvement
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
description: >-
Rare systemic extension of R. akari disease can include self-limited
acute hepatitis.
- name: Macrophage Cytokine Response to Rickettsia akari
description: >-
R. akari can infect macrophages with little direct macrophage cytotoxicity
while increasing release of IL-1 beta and IL-6, linking the initial
mononuclear-cell compartment to a local and systemic proinflammatory response.
cell_types:
- preferred_term: macrophage
term:
id: CL:0000235
label: macrophage
biological_processes:
- preferred_term: cytokine production
term:
id: GO:0001816
label: cytokine production
modifier: INCREASED
evidence:
- reference: PMID:11953398
reference_title: "Rickettsia-macrophage interactions: host cell responses to Rickettsia akari and Rickettsia typhi."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
Host cells responded to rickettsial infection with increased secretion of
proinflammatory cytokines such as interleukin-1beta (IL-1beta) and IL-6.
explanation: >-
Infected macrophage cultures secreted proinflammatory cytokines after
R. akari or R. typhi exposure.
downstream:
- target: Inoculation Eschar Formation
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
description: Cytokine production contributes to local eschar inflammation.
- target: Papulovesicular Exanthem
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
description: Cytokine production contributes to systemic exanthem formation.
- target: Fever
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
description: Proinflammatory cytokine production contributes to systemic fever.
- name: Inoculation Eschar Formation
description: >-
The local bite-site vesicle dries to an inoculation eschar, forming the
early dermal lesion that marks the site of mite inoculation.
role: consequence
evidence:
- reference: PMID:28846279
reference_title: Rickettsia akari (Rickettsialpox).
supports: SUPPORT
evidence_source: OTHER
snippet: >-
One week after a mite bite, a vesicle appears, which dries up, leaving an eschar.
The rash is often papular but can also be vesicular, hence the name
rickettsialpox.
explanation: >-
Describes the bite-site vesicle that dries to form a rickettsialpox eschar.
downstream:
- target: Eschar
causal_link_type: DIRECT
description: The bite-site lesion forms an eschar.
- name: Small-Vessel Vasculitis
description: >-
Endothelial infection and vascular leak in systemic rickettsialpox progress
into the small-vessel lymphohistiocytic vasculitis that can support the
disseminated rash.
role: vascular_response
biological_scale: TISSUE
cell_types:
- preferred_term: vascular endothelial cell
term:
id: CL:0002139
label: endothelial cell of vascular tree
biological_processes:
- preferred_term: inflammatory response
modifier: INCREASED
term:
id: GO:0006954
label: inflammatory response
- preferred_term: positive regulation of vascular permeability
modifier: INCREASED
term:
id: GO:0043117
label: positive regulation of vascular permeability
evidence:
- reference: PMID:2677080
reference_title: Rickettsioses of the spotted fever group around the world.
supports: SUPPORT
evidence_source: OTHER
quote_role: REVIEW_SYNTHESIS
snippet: >-
These obligate intracellular bacteria invade vascular endothelial cells, which
are damaged directly, causing increased vascular permeability.
explanation: >-
The review ties SFG endothelial damage to the vascular leak that underlies
downstream vasculitic skin lesions.
downstream:
- target: Papulovesicular Exanthem
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
description: Cutaneous small-vessel vasculitis contributes to the exanthem.
- name: Papulovesicular Exanthem
description: >-
Systemic rickettsial spread is followed by a generalized papular or
vesicular eruption, the visible systemic cutaneous signature of
rickettsialpox.
role: consequence
evidence:
- reference: PMID:14676069
reference_title: >-
Increased detection of rickettsialpox in a New York City hospital following
the anthrax outbreak of 2001: use of immunohistochemistry for the rapid
confirmation of cases in an era of bioterrorism.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Immunohistochemical testing revealed spotted fever group rickettsiae in all 16
eschars and in 5 of the 9 papulovesicles tested.
explanation: >-
The 18-patient New York City series confirms that papulovesicles in
rickettsialpox contain SFG rickettsial antigen.
downstream:
- target: Papulovesicular eruption
causal_link_type: DIRECT
description: The rickettsialpox exanthem is papular to vesicular.
- name: Rare Hepatic Involvement
description: >-
Rickettsialpox can rarely involve the liver and present with acute hepatitis
that resolves completely.
role: consequence
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In this report, we describe two patients with rickettsialpox who had acute
hepatitis that resolved completely.
explanation: >-
Reports acute, self-limited hepatitis in two rickettsialpox patients.
downstream:
- target: Acute hepatitis
causal_link_type: DIRECT
description: Hepatic involvement presents clinically as acute hepatitis.
phenotypes:
- category: Clinical
name: Fever
frequency: FREQUENT
description: Fever is part of the acute syndrome of rickettsialpox.
phenotype_term:
preferred_term: Fever
term:
id: HP:0001945
label: Fever
evidence:
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Samples were collected from patients with febrile illnesses accompanied by an
eschar, a papulovesicular rash, or both.
explanation: >-
The New York City case cluster was ascertained through febrile illnesses
with eschars or papulovesicular rash.
- category: Dermatologic
name: Eschar
frequency: FREQUENT
description: A bite-site vesicle can dry into an inoculation eschar.
phenotype_term:
preferred_term: Eschar
term:
id: HP:6000793
label: Eschar
evidence:
- reference: PMID:14676069
reference_title: >-
Increased detection of rickettsialpox in a New York City hospital following
the anthrax outbreak of 2001: use of immunohistochemistry for the rapid
confirmation of cases in an era of bioterrorism.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Immunohistochemical testing revealed spotted fever group rickettsiae in all 16
eschars and in 5 of the 9 papulovesicles tested.
explanation: >-
The 18-patient New York City series confirms that eschars in clinically
diagnosed rickettsialpox contain SFG rickettsial antigen.
- category: Dermatologic
name: Papulovesicular eruption
frequency: FREQUENT
description: The generalized exanthem is often papular and can be vesicular.
phenotype_term:
preferred_term: Papulovesicular eruption
term:
id: HP:0033700
label: Papulovesicular eruption
evidence:
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Samples were collected from patients with febrile illnesses accompanied by an
eschar, a papulovesicular rash, or both.
explanation: >-
The New York City case cluster used papulovesicular rash among its
clinical ascertainment features.
- reference: PMID:14676069
reference_title: >-
Increased detection of rickettsialpox in a New York City hospital following
the anthrax outbreak of 2001: use of immunohistochemistry for the rapid
confirmation of cases in an era of bioterrorism.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Immunohistochemical testing revealed spotted fever group rickettsiae in all 16
eschars and in 5 of the 9 papulovesicles tested.
explanation: >-
Papulovesicles tested from clinically diagnosed rickettsialpox patients
contained SFG rickettsial antigen.
- category: Gastrointestinal
name: Acute hepatitis
frequency: OCCASIONAL
description: Acute hepatitis is an uncommon, self-resolving systemic complication.
phenotype_term:
preferred_term: Acute hepatitis
term:
id: HP:0200119
label: Acute hepatitis
evidence:
- reference: PMID:18171106
reference_title: Hepatitis in association with rickettsialpox.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In this report, we describe two patients with rickettsialpox who had acute
hepatitis that resolved completely.
explanation: >-
Case reports establish acute self-limited hepatitis as a rare complication
of rickettsialpox.
diagnosis:
- name: Skin-lesion immunohistochemistry or molecular confirmation
description: >-
Rickettsialpox can be confirmed from eschar or papular lesion biopsies by
immunohistochemical staining for spotted-fever-group rickettsiae, R. akari
PCR amplification, or organism isolation in cell culture.
diagnosis_term:
preferred_term: skin biopsy immunostaining or PCR
term:
id: NCIT:C18020
label: Diagnostic Procedure
results: Detection of rickettsial antigen, R. akari DNA, or cultured R. akari confirms infection.
evidence:
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
During February 2001 through August 2002, 34 cases of rickettsialpox in NYC were
confirmed at CDC from cutaneous biopsy specimens tested by using
immunohistochemical (IHC) staining, PCR analysis, and isolation of Rickettsia
akari in cell culture, as well as an indirect immunofluorescence assay of serum
specimens.
explanation: >-
The CDC-confirmed case cluster used lesion immunostaining, PCR, culture, and
paired serology to confirm rickettsialpox.
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The 17-kDa protein gene sequence of R. akari was amplified from eschars of five
patients. Four isolates of R. akari were obtained from cutaneous lesions.
explanation: >-
Confirms that lesional skin can yield both R. akari sequence and live
isolates.
- name: Paired-serum indirect immunofluorescence assay
description: >-
Paired acute and convalescent sera can confirm rickettsialpox when indirect
immunofluorescence shows a fourfold or greater rise in antibodies reactive
with R. akari.
diagnosis_term:
preferred_term: serologic testing
term:
id: NCIT:C25294
label: Laboratory Procedure
results: A fourfold or greater rise in antibody titer to R. akari confirms infection retrospectively.
evidence:
- reference: PMID:12860597
reference_title: "Rickettsialpox in New York City: a persistent urban zoonosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Of the eleven patients for whom paired serum samples were obtained, all
demonstrated fourfold or greater increases in antibody titers reactive with R.
akari.
explanation: >-
Paired serum specimens confirmed rickettsialpox by a fourfold antibody
rise to R. akari in every paired sample from the New York City series.
treatments:
- name: Doxycycline pharmacotherapy
description: >-
Empiric doxycycline treats suspected spotted-fever-group rickettsioses,
including rickettsialpox, by combining intracellular penetration with
inhibition of the rickettsial 30S ribosomal subunit.
treatment_term:
preferred_term: Pharmacotherapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: doxycycline
term:
id: CHEBI:50845
label: doxycycline
therapeutic_modality: SMALL_MOLECULE
target_mechanisms:
- target: Rickettsia akari Ribosomal Translation
description: Doxycycline inhibits bacterial protein synthesis at the 30S ribosomal subunit.
- target: Obligate Intracellular Rickettsia akari Niche
description: Doxycycline is cell-penetrant and can reach intracellular R. akari.
evidence:
- reference: PMID:2677080
reference_title: Rickettsioses of the spotted fever group around the world.
supports: SUPPORT
evidence_source: OTHER
quote_role: REVIEW_SYNTHESIS
snippet: >-
Empiric treatment with doxycycline, tetracycline, or chloramphenicol should be
given early in the course on the basis of clinical suspicion of the diagnosis of
a SFG rickettsiosis.
explanation: >-
The review includes rickettsialpox among spotted-fever-group rickettsioses
and recommends empiric doxycycline for suspected SFG disease.
Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.
Create: Rickettsialpox · 2026-09-25T12:07:34Z · View source
Created a standalone Rickettsialpox entry for MONDO:0019360 after exact ignored-file-inclusive local search found it only as a Spotted_Fever_Rickettsiosis subtype, Boomer analysis row, and rare-disease ICD worklist row. The only GitHub overlaps were the completed root curation issue/PR (#8890/#8899), whose root entry intentionally left rickettsialpox promotable; no active local or remote branch was found. PROMOTION. Kept Rickettsialpox under the Spotted fever rickettsiosis parent and updated the Rickettsialpox subtype description there from "No standalone dismech entry yet" to `Curated in full in Rickettsialpox.yaml`. DEEP RESEARCH. Ran `just research-disorder openscientist Rickettsialpox`; the report is `research/Rickettsialpox-deep-research-openscientist.md`, with the generated citation table and HTML/PDF artifacts committed alongside it. The report resolved all 13 references, but term validation correctly flagged several lead-quality CURIE errors: `NCIT:C842` for "Tetracycline antibiotic" resolves to Stanozolol, `NCIT:C242` for "Broad-spectrum; 50S ribosome inhibitor" resolves to Anti-Androgen, and `NCIT:C312` for doxycycline resolves to Bleomycin Sulfate. None were used. Doxycycline was instead modeled with the existing CHEBI:50845 agent under NCIT:C15986 Pharmacotherapy, following the nearby rickettsiosis treatment pattern. NEC. `just preflight-dr research/Rickettsialpox-deep-research-openscientist.md MONDO:0019360` returned SKIP because MONDO records no RO:0004003 causal gene for this acquired infection. Manual identity review matched the report to rickettsialpox throughout: MONDO:0019360, Rickettsia akari (NCBITaxon:786), mite-borne transmission, and the core New York City rickettsialpox case series all refer to the intended entity. CONTENT. Curated the Rickettsia akari infectious agent, house mouse mite transmission, the conserved intracellular and 70S-ribosome drug-mechanism module conformances, cutaneous R. akari infection, macrophage cytokine response, papulovesicular rash/eschar formation, and rare hepatic involvement. Added four phenotype nodes and wired all four to causal parents: fever, eschar, papulovesicular eruption, and rare acute hepatitis. Added diagnosis by lesional skin immunohistochemistry/PCR/culture and paired-serum indirect immunofluorescence. Added empiric doxycycline treatment targeting both the rickettsial ribosome node and the obligate intracellular niche. SOURCES. Reused existing cached rickettsialpox/Rickettsia akari evidence where exact snippets already supported the claim, and lifted three central sources from the OpenScientist report: Koss et al. for the 18-patient New York City diagnostic series (PMID:14676069), Madison et al. for rare self-limited hepatitis and the concise agent/vector statement (PMID:18171106), and Walker's spotted-fever-group review for the endothelial-invasion and doxycycline claims (PMID:2677080). Orphanet lists Rickettsialpox as ORPHA:83312 in the rare-disease ICD worklist, but `just fetch-reference ORPHA:83312` reported "No source found for reference type"; no hand-written Orphanet cache was created. VALIDATION. `just validate kb/disorders/Rickettsialpox.yaml` passed with 21 snippets checked, no skipped or unavailable snippets, and 24 titles checked. `just count-verified-snippets kb/disorders/Rickettsialpox.yaml` reported 21/21 snippets verified against cached references. `just list-disconnected-phenotypes kb/disorders/Rickettsialpox.yaml` reported 4/4 phenotype nodes causally connected. `just validate kb/disorders/Spotted_Fever_Rickettsiosis.yaml` passed after the parent row pointer edit.
Rickettsialpox is a mild, self-limited febrile spotted fever group (SFG) rickettsiosis caused by the obligate intracellular bacterium Rickettsia akari, transmitted to humans by the bite of the house-mouse mite Liponyssoides sanguineus, whose natural reservoir is the common house mouse (Mus musculus). It is an infectious, non-heritable urban zoonosis first described in New York City in 1946 and remains endemic there today. After an incubation period of roughly 9–14 days, patients develop a painless inoculation eschar at the mite-bite site, followed by abrupt fever, headache, chills, myalgia, and regional lymphadenopathy, and then a generalized papulovesicular ("chickenpox-like") rash. The illness resolves over 2–3 weeks, systemic complications (e.g., self-limited hepatitis) are rare, and no deaths have been attributed to the disease.
The pathophysiology is shared across the spotted fever group: R. akari invades vascular endothelial cells, damaging them directly, increasing vascular permeability, and producing a small-vessel lymphohistiocytic vasculitis that underlies both the local eschar and the disseminated rash. Diagnosis relies on the clinical triad (eschar + fever + papulovesicular rash), skin-biopsy immunohistochemistry demonstrating SFG rickettsiae, indirect immunofluorescence serology (a four-fold IgG rise or a single titer ≥1:64), and increasingly on PCR of eschar or lesion material (gltA, ompA, ompB, 17-kDa genes). Empiric doxycycline is curative and produces rapid defervescence; the prognosis is excellent.
Because rickettsialpox is not a nationally notifiable disease in the United States, it is widely under-diagnosed and under-reported; reported incidence tracks clinician awareness rather than true disease burden. Prevention is entirely environmental — rodent population control, mite/vector control with acaricides, and improved dwelling sanitation. There is no vaccine, no genetic susceptibility component, and no Mendelian OMIM/Orphanet entry, because the disease is infectious rather than heritable. Serologic evidence of R. akari exposure in urban dogs and cats supports a One Health, urban-rodent ecology and a broader geographic footprint than the classic New York foci.
This report is organized against the 15-section disease-characteristics template. Sections tied to genetic disease (causal genes, pathogenic variants, inheritance, model organisms of a heritable condition) are explicitly marked Not applicable because rickettsialpox is an acquired infection.
Rickettsialpox is caused by Rickettsia akari, an obligate intracellular, Gram-negative bacterium of the spotted fever group, and is transmitted to humans by the bite of the mite Liponyssoides sanguineus (formerly Allodermanyssus sanguineus), which infests the common house mouse Mus musculus. The causal chain — agent, vector, reservoir — is well established in primary literature. As stated directly: "Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia akari and transmitted by Liponyssoides sanguineus, a mite that infests the common house mouse, Mus musculus" PMID: 18171106.
Serologic and immunohistochemical confirmation of R. akari as the etiologic agent in human cases was documented in a consecutive New York City hospital case series: "A 4-fold or greater increase in IgG antibody titers reactive with Rickettsia akari was observed in all 9 patients for whom acute and convalescent phase samples were available" PMID: 14676069. Because transmission is mite-borne rather than tick-borne, rickettsialpox is unusual among SFG rickettsioses; the mite vector both maintains the organism transovarially and delivers it during blood feeding.
Evidence type: human clinical / serologic (aggregated case series). Organism terms: Rickettsia akari (NCBITaxon:786); Mus musculus (NCBITaxon:10090); vector Liponyssoides sanguineus.
Rickettsialpox presents as a self-limited febrile illness defined by two hallmark skin lesions: an inoculation eschar and a generalized papulovesicular rash. In a consecutive NYC series of 18 patients (2001–2002), immunohistochemistry detected SFG rickettsiae in the great majority of lesions: "Immunohistochemical testing revealed spotted fever group rickettsiae in all 16 eschars and in 5 of the 9 papulovesicles tested" PMID: 14676069. The disease is clinically important because it mimics more dangerous conditions: "Rickettsialpox is a self-limited febrile illness with skin lesions that may be mistaken for signs of potentially more serious diseases, such as cutaneous anthrax or chickenpox" PMID: 14676069. Notably, 50% of that series presented in the five months after the October 2001 anthrax bioterrorism events, indicating that heightened clinician awareness — not a true rise in incidence — drove detection.
Systemic complications are uncommon but recognized; self-resolving hepatitis has been reported: "we describe two patients with rickettsialpox who had acute hepatitis that resolved completely" PMID: 18171106.
Evidence type: human clinical case series.
The core pathophysiology is shared with the entire spotted fever group. In David Walker's authoritative SFG review, "These obligate intracellular bacteria invade vascular endothelial cells, which are damaged directly, causing increased vascular permeability" PMID: 2677080, and an eschar forms at the site of the vector bite. Mechanistic studies of related SFG rickettsiae (R. conorii, R. parkeri) confirm the shared pathogenic program that is inferred to apply to R. akari: preferential tropism for microvascular endothelium producing barrier dysfunction and increased permeability. "Obligate intracellular bacteria which exhibit preferential tropism for host microvascular endothelium in the mammalian hosts, resulting in disease manifestations attributed primarily to endothelial damage or dysfunction" PMID: 32977742; and "vascular inflammation and dysfunction represent salient features of rickettsial pathogenesis" PMID: 33003310.
Downstream molecular events characterized in SFG models include mTOR (mTORC1/mTORC2) activation in infected human endothelial cells PMID: 33003310, and endothelial secretome/exosome changes that drive barrier dysfunction and edema PMID: 31955791, PMID: 33975935.
Evidence type: authoritative review (human) + in vitro/in vivo mechanistic studies of related SFG species (inferred to R. akari).
Diagnosis relies on serology and biopsy immunohistochemistry, and empiric doxycycline is curative. Per Walker: "Rickettsiae are demonstrable by diagnostic immunohistology in biopsies of rash or eschar. Empiric treatment with doxycycline, tetracycline, or chloramphenicol should be given early in the course on the basis of clinical suspicion" PMID: 2677080. The NYC series demonstrated diagnosis by IHC of paraffin-embedded skin biopsy (SFG rickettsiae in 16/16 eschars and 5/9 papulovesicles) and by indirect immunofluorescence serology (four-fold IgG rise or single titer ≥1:64) PMID: 14676069. Serology cross-reacts broadly across the SFG (e.g., R. rickettsii antigen can be used as a screen). Rickettsialpox is self-limited even without treatment, with no reported deaths, and doxycycline produces rapid resolution.
Evidence type: authoritative review + human case series.
Urban companion animals show measurable R. akari seroreactivity, supporting a One Health, urban-rodent ecology and a broad geographic distribution. In New York City dogs, "Cross-absorption testing indicated that in 6 of 7 samples, infection was caused by R akari. Results suggest that dogs can be naturally infected with R akari" PMID: 11394829; 7.7% of 311 dogs were EIA-positive for SFG rickettsiae, with tick infestation and increasing age as significant risk factors. Among 170 US cats, seroprevalence was "14.9% for R akari" PMID: 16434226. Human SFG seroreactivity including R. akari was also detected in a Papua New Guinea serosurvey PMID: 16450784, indicating exposure beyond the classic foci.
Evidence type: veterinary/human seroepidemiology.
The classic natural history is a ~9–14 day incubation, a painless inoculation eschar, then fever/headache and a generalized papulovesicular rash resolving over 2–3 weeks. A mite bite produces a painless papule that becomes a vesicle and then a black-crusted eschar (IHC-positive in 16/16 eschars in the Koss series) PMID: 14676069. After incubation, patients develop abrupt fever, chills, headache, myalgia, and often regional lymphadenopathy, followed within 2–3 days by a generalized papulovesicular eruption (IHC-positive in 5/9 papulovesicles). Eschar formation at the vector inoculation site is a defining SFG feature: "Eschar occurs in some SFG rickettsioses at the site of tick bite" PMID: 2677080. The illness is acute and self-limited; systemic complications are rare (occasional self-resolving hepatitis) PMID: 18171106.
Rickettsialpox is not nationally notifiable in the US and is regarded as under-diagnosed and under-reported; reported incidence tracks clinician awareness. The NYC authors concluded: "Rickettsialpox remains endemic in New York City, and the bioterrorism attacks of October 2001 may have led to increased awareness and detection of this disease" PMID: 14676069. The disease occurs where humans contact the rodent-associated mite: "The hematophagic-biting mite, Liponyssoides sanguineus, is a mite of the rat, mouse, and other domestic rodents but can also bite humans" PMID: 17114713, with ectoparasite exposure heightened in homeless and inner-city populations. Prevention is achieved through rodent population control, mite/vector control (acaricides), and improved sanitation.
Rickettsialpox is classified as an infectious spotted fever group rickettsiosis, not a genetic disease. Phylogenetic analysis of the citrate synthase (gltA) gene places the mite-borne organism within the SFG cluster: "the mite-borne organism Rickettsia akari were associated with the SFG cluster" PMID: 9103608. Standard identifiers: MONDO:0019360; ICD-10 A79.1 (Rickettsialpox due to Rickettsia akari); MeSH D012288; pathogen NCBITaxon:786. There is no OMIM or Orphanet Mendelian entry because the disease is infectious. Synonyms include vesicular rickettsiosis and Kew Gardens spotted fever.
Overview. Rickettsialpox is an acute, mild, self-limited febrile illness caused by Rickettsia akari and transmitted by the mite Liponyssoides sanguineus PMID: 18171106. It is characterized by an inoculation eschar and a disseminated papulovesicular rash, and it resolves without sequelae.
Key identifiers. MONDO:0019360; ICD-10 A79.1; MeSH D012288 (Rickettsialpox); pathogen taxon NCBITaxon:786 (Rickettsia akari). No OMIM or Orphanet entry (non-heritable, infectious disease).
Synonyms / alternative names. Vesicular rickettsiosis; Kew Gardens spotted fever; Rickettsia akari infection.
Information source. Derived predominantly from aggregated disease-level resources and hospital case series (e.g., the New York City consecutive series, PMID 14676069) plus authoritative SFG reviews — not individual EHR-level datasets.
| Phenotype | Type | Suggested HPO | Frequency / notes |
|---|---|---|---|
| Inoculation eschar (tache noire) | Physical skin sign | HP:0200042 (Skin ulcer) / eschar | Nearly universal; IHC-positive 16/16 eschars PMID: 14676069 |
| Papulovesicular ("chickenpox-like") rash | Physical skin manifestation | HP:0000988 (Skin rash); HP:0200037 (Vesicle) | Generalized; IHC-positive 5/9 papulovesicles PMID: 14676069 |
| Fever | Symptom | HP:0001945 (Fever) | Abrupt, near-universal PMID: 14676069 |
| Headache | Symptom | HP:0002315 (Headache) | Common |
| Chills / myalgia | Symptom | HP:0025143 (Chills); HP:0003326 (Myalgia) | Common |
| Regional lymphadenopathy | Clinical sign | HP:0002716 (Lymphadenopathy) | Frequent |
| Hepatitis (elevated transaminases) | Laboratory / organ | HP:0200119 (Hepatitis) | Uncommon, self-resolving PMID: 18171106 |
Onset: adult-onset in most reported cases (exposure-dependent, any age). Severity: mild to moderate. Progression: acute, self-limited, resolving over 2–3 weeks. Quality-of-life impact: minimal and transient; full recovery is the norm.
Not applicable. Rickettsialpox is an infectious disease with no causal human genes, pathogenic variants, modifier genes, epigenetic drivers, or chromosomal abnormalities. Molecular characterization pertains to the pathogen genome (SFG classification by gltA/citrate synthase phylogeny PMID: 9103608), not the host.
Ordered causal chain (initiating lesion → clinical manifestation):
1. Infected mite (Liponyssoides sanguineus) bites human skin
└─ inoculates R. akari into the dermis
↓ leads to
2. R. akari attaches to and invades local vascular endothelial cells
(obligate intracellular replication)
↓ results in
3. Direct endothelial cell damage + local dermal infection/necrosis
↓ leads to
4. Formation of the inoculation ESCHAR at the bite site
│
├─ (branch, local) eschar = tache noire
│
↓ concurrently, hematogenous / lymphatic dissemination
5. Systemic seeding of microvascular endothelium in skin and organs
↓ leads to
6. Endothelial barrier dysfunction + increased vascular permeability
(mTORC1/2 activation; secretome/exosome changes — shown in SFG models,
inferred for R. akari)
↓ results in
7. Small-vessel LYMPHOHISTIOCYTIC VASCULITIS
↓ produces
8. Clinical manifestations: fever, headache, myalgia, lymphadenopathy,
and the disseminated PAPULOVESICULAR RASH
│
└─ (rare branch) hepatic endothelial involvement → self-limited hepatitis
Note: Steps 6–7's molecular detail is demonstrated primarily in related SFG species (R. conorii, R. parkeri) and is inferred to apply to R. akari, which shares the endothelial-tropism program PMID: 2677080, PMID: 32977742.
| Intervention | Class / mechanism | Suggested NCIT | Evidence |
|---|---|---|---|
| Doxycycline (first-line) | Tetracycline; inhibits bacterial 30S ribosome / protein synthesis | NCIT:C312 (Doxycycline) | PMID: 2677080 |
| Tetracycline | Tetracycline antibiotic | NCIT:C842 | PMID: 2677080 |
| Chloramphenicol | Broad-spectrum; 50S ribosome inhibitor (alternative) | NCIT:C242 | PMID: 2677080 |
Empiric doxycycline should be started early on clinical suspicion and produces rapid defervescence PMID: 2677080. No gene, cell, RNA, or immunotherapy is relevant. No pharmacogenomic modifiers are established. Supportive care (antipyretics) is adjunctive. Because the disease is self-limited, treatment mainly shortens symptomatic duration.
Because rickettsialpox is infectious, "model organisms" refer to infection models, not genetic disease models. Murine models of SFG rickettsiosis (e.g., R. conorii and R. parkeri in mice) recapitulate endothelial infection, vascular permeability, and disease severity, and have been used to test mechanistic interventions — for example, the calcium-channel blocker benidipine converted sublethal to lethal R. parkeri infection by impairing innate immunity PMID: 38408129. Primary human umbilical vein endothelial cells (HUVEC) serve as the standard in vitro model for endothelial infection, secretome, and mTOR signaling studies PMID: 31955791, PMID: 33003310. These models capture the shared SFG endothelial pathogenesis but are largely developed for more virulent species; R. akari-specific models are sparse, and its intrinsically mild phenotype limits severity-focused modeling.
The disease can be read as a single mechanistic story with one local branch and one systemic branch, both flowing from a single lesion — endothelial infection.
| Stage | Location | Key event | Manifestation |
|---|---|---|---|
| Inoculation | Skin (bite site) | Mite deposits R. akari | (none yet) |
| Local infection | Dermal microvasculature | Endothelial invasion + necrosis | Eschar |
| Dissemination | Blood / lymph | Hematogenous spread | Incubation → fever onset |
| Systemic infection | Microvascular endothelium (skin, organs) | Barrier dysfunction, ↑permeability, mTOR activation | Fever, headache, myalgia |
| Vasculitis | Small vessels | Lymphohistiocytic perivascular infiltrate | Papulovesicular rash |
| Rare extension | Hepatic endothelium | Focal inflammation | Self-limited hepatitis |
| Resolution | Systemic | Immune clearance ± doxycycline | Recovery in 2–3 weeks |
The unifying insight is that R. akari is a comparatively avirulent member of a virulent family. It uses the same endothelial-tropism program as R. conorii and R. rickettsii — invade endothelium, damage it, increase vascular permeability, trigger small-vessel vasculitis — but produces a mild, self-limited disease with near-zero mortality. The clinical hallmarks (eschar + papulovesicular rash) map directly onto the local and systemic branches of endothelial infection. This makes rickettsialpox both a diagnostic mimic (chickenpox, cutaneous anthrax) and an informative "benign end" of the SFG severity spectrum.
| PMID | Title (abbrev.) | Role in this report |
|---|---|---|
| 14676069 | Increased detection of rickettsialpox in a NYC hospital (2001 anthrax era) | Core human case series: IHC diagnosis (16/16 eschars, 5/9 papulovesicles), serology criteria, endemicity, differentials, under-reporting |
| 18171106 | Hepatitis in association with rickettsialpox | Etiology/vector/reservoir statement; rare self-limited hepatitis |
| 2677080 | Rickettsioses of the spotted fever group around the world (Walker review) | Endothelial-invasion mechanism; eschar; biopsy IHC diagnosis; doxycycline/tetracycline/chloramphenicol treatment |
| 32977742 | Comparative transcriptomics of R. conorii | Microvascular endothelial tropism / endothelial damage (SFG-wide, inferred to R. akari) |
| 33003310 | mTOR activation in infected human endothelial cells | Downstream signaling; vascular inflammation as core SFG feature |
| 31955791 | Endothelial secretome proteomics (RC0497) | Secretome/barrier dysfunction; candidate diagnostic marker |
| 33975935 | Endothelial exosome in rickettsial infection | Barrier dysfunction/edema mechanism |
| 38408129 | Benidipine impairs innate immunity (mouse R. parkeri) | Immune control; infection model relevance |
| 11394829 | R. akari serology in NYC dogs | One Health ecology; natural canine infection (6/7 cross-absorbed) |
| 16434226 | Vector-borne pathogen serology in cats | 14.9% feline R. akari seroprevalence |
| 16450784 | Rickettsial antibody survey, Papua New Guinea | SFG/R. akari exposure beyond classic foci |
| 17114713 | Arthropod-borne diseases in homeless | Rodent-mite exposure pathway; prevention rationale |
| 9103608 | Citrate synthase (gltA) phylogeny | Classification of R. akari within SFG |
Evidence types span human clinical case series (14676069, 18171106), authoritative reviews (2677080), in vitro/in vivo mechanistic studies of related SFG species (32977742, 33003310, 31955791, 33975935, 38408129), seroepidemiology (11394829, 16434226, 16450784), and molecular phylogeny (9103608).
Report compiled from an autonomous 5-iteration investigation: 8 confirmed findings, 46 papers reviewed. Rickettsialpox is treated throughout as an infectious, non-heritable zoonosis; genetic/inheritance template sections are marked Not Applicable accordingly.
Checked with linkml-reference-validator 0.3.0rc1.
| Outcome | Count |
|---|---|
| References checked | 13 |
| Resolved | 13 |
| Unresolved (possible confabulation) | 0 |
| Unverifiable | 0 |
| References weighed for topical relevance | 13 |
| On topic | 6 |
| Off topic | 0 |
All extracted references resolved successfully.
Checked with linkml-term-validator 0.4.5, through the ols: adapter.
| Outcome | Count |
|---|---|
| Terms checked | 22 |
| Resolved | 22 |
| Unresolved (possible confabulation) | 0 |
| Obsolete | 0 |
| Unverifiable | 0 |
| Terms whose name was checked | 16 |
| Terms named correctly | 5 |
| Terms named as a different term | 5 |
| Terms whose name is worth a second look | 6 |
These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:
NCBITaxon:10090 (2 mentions) - the report calls it "Mus musculus", "Reservoir host: house mouse *Mus musculus"; NCBITaxon calls it Mus musculus**UBERON:0001981 (1 mention) - the report calls it "Vascular system: small blood vessels / microvasculature"; UBERON calls it blood vessel**UBERON:0002107 (1 mention) - the report calls it "Secondary organ involvement: liver"; UBERON calls it liver**NCIT:C842 (1 mention) - the report calls it "Tetracycline antibiotic"; NCIT calls it StanozololNCIT:C242 (1 mention) - the report calls it "Broad-spectrum; 50S ribosome inhibitor (alternative)"; NCIT calls it Anti-AndrogenThe report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:
NCBITaxon:786 (4 mentions) - the report calls it "Rickettsia akari", "Infectious agent: *Rickettsia akari"; NCBITaxon calls it Rickettsia akari**HP:0200119 (1 mention) - the report calls it "Hepatitis"; HP calls it Acute hepatitisCL:0000115 (2 mentions) - the report calls it "Cell level: vascular endothelial cells"; CL calls it endothelial cell**GO:0044409 (1 mention) - the report calls it "entry into host"; GO calls it symbiont entry into host, and lists "entry into host" among its other namesUBERON:0002097 (1 mention) - the report calls it "Primary organ/tissue: skin"; UBERON calls it skin of body**, and lists "entire skin" among its other namesNCIT:C312 (1 mention) - the report calls it "Doxycycline"; NCIT calls it Bleomycin Sulfate, and lists "BleMomycine" among its other namesThe report gives these identifiers more than one name of its own:
NCBITaxon:786 - called "Rickettsia akari", "Infectious agent:* Rickettsia akari"NCBITaxon:10090 - called "Mus musculus", "Reservoir host:* house mouse Mus musculus"