Acne Vulgaris

Complex MONDO:0011438 Pathograph 17 Show in embeddings browser Inflammatory skin disease Pilosebaceous unit disorder

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit, usually affecting the face and trunk, that produces comedones with variable papules, pustules, nodules, pigmentary sequelae, and scarring. The canonical model involves interacting follicular differentiation and keratinization, androgen-responsive sebaceous activity, Cutibacterium acnes community or strain-dependent immune signaling, and inflammation rather than a simple bacterial infection. Recent human genetics and spatial-transcriptomic data additionally prioritize follicular stem/progenitor maintenance, cellular migration, and lesion-state-specific sebaceous differentiation, so the ordering of the major processes remains incompletely resolved.

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1
Inheritance
6
Pathophys.
6
Phenotypes
2
Hypotheses
1
Gaps
17
Pathograph
8
Medical Actions
2
Differentials
3
Datasets
26
References
2
Deep Research
👪

Inheritance

1
Polygenic inheritance HP:0010982
Common acne has high familial heritability and a polygenic, multifactorial architecture. No single-gene Mendelian model explains acne vulgaris in the general population.
Polygenic inheritance
Show evidence (2 references)
PMID:37662507 SUPPORT Other
"The phenomenon is influenced by polygenic inheritance or can be ascribed to the interplay between multiple genes and environmental factors."
The genetics review explicitly characterizes acne as polygenic and multifactorial.
PMID:23210645 PARTIAL Other
"The heritability of acne is almost 80% in first-degree relatives."
Familial epidemiology supports a substantial inherited component without identifying a Mendelian cause.
◈

Mechanistic Hypotheses

2
Canonical Multifactorial Pilosebaceous Model
canonical_pilosebaceous_interaction CANONICAL
Evidence balance 1 support
Follicular keratinization, androgen-responsive sebaceous activity, microbial community or strain effects, and innate/adaptive inflammation interact to produce acne lesions. These processes need not occur in one invariant linear order.
Pathograph links
Lesion-Context-Dependent Sebaceous Lipid Dysregulation -> Follicular Retention Hyperkeratosis and Microcomedone Formation UNKNOWN Comedonal lesions show increased sebogenesis, but the direction and necessity of this relationship remain uncertain.
Follicular Retention Hyperkeratosis and Microcomedone Formation -> Comedones UNKNOWN Retention hyperkeratosis and microcomedone enlargement produce the clinically visible comedonal lesion.
C. acnes Community and Strain-Dependent Immune Signaling -> Early and Sustained Pilosebaceous Inflammation INDIRECT KNOWN INTERMEDIATES Acne-associated strains can activate keratinocyte/sebocyte innate immune pathways through porphyrin, potassium-leakage, TLR2, and NLRP3 mechanisms. Intermediates: strain-dependent porphyrin production; potassium leakage; NLRP3 inflammasome activation
Early and Sustained Pilosebaceous Inflammation -> Comedones UNKNOWN Subclinical inflammation may participate before visible comedones, but its causal role in comedogenesis remains uncertain.
Early and Sustained Pilosebaceous Inflammation -> Inflammatory papules INDIRECT UNKNOWN INTERMEDIATES Pilosebaceous inflammation produces a raised erythematous inflammatory lesion through tissue infiltration and edema.
Early and Sustained Pilosebaceous Inflammation -> Pustules INDIRECT KNOWN INTERMEDIATES Neutrophil recruitment into an inflamed follicular lesion produces pustular morphology. Intermediates: neutrophil recruitment
Early and Sustained Pilosebaceous Inflammation -> Post-Inflammatory Hyperpigmentation INDIRECT KNOWN INTERMEDIATES Acne inflammation can stimulate melanogenesis and abnormal melanin deposition after active lesions without requiring deep follicular rupture. Intermediates: excess melanogenesis; abnormal melanin deposition
Early and Sustained Pilosebaceous Inflammation -> Deep Follicular Inflammation, Rupture, and Repair INDIRECT UNKNOWN INTERMEDIATES Persistent or deep inflammation can disrupt the follicular wall and initiate dermal inflammatory repair.
Deep Follicular Inflammation, Rupture, and Repair -> Nodules and Cysts UNKNOWN Deep inflammatory acne manifests clinically as nodular or cystic lesions.
Deep Follicular Inflammation, Rupture, and Repair -> Atrophic Acne Scarring INDIRECT UNKNOWN INTERMEDIATES Dermal injury and remodeling after inflammatory acne can produce permanent atrophic scars.
Show evidence (1 reference)
DOI:10.1007/s13555-023-01079-8 SUPPORT Other
"C. acnes acts in interplay with three other major patho-genetic factors, namely androgen-dependent hyperseborrhea, follicular keratinocyte hyper-proliferation, and inflammation [ 10, 11]."
The review describes the canonical factors as interacting contributors.
Follicular Stem/Progenitor and Differentiation Model
follicular_lineage_dysregulation EMERGING
Evidence balance 2 support
Polygenic susceptibility may primarily disturb follicular stem/progenitor maintenance, cell migration, and pilosebaceous differentiation, with keratinization, sebaceous-state changes, and inflammation emerging in lesion-specific combinations.
Pathograph links
Abnormal Pilosebaceous Differentiation -> Follicular Retention Hyperkeratosis and Microcomedone Formation UNKNOWN Follicular lineage and migration abnormalities may promote retention hyperkeratosis and microcomedone initiation.
Abnormal Pilosebaceous Differentiation -> Lesion-Context-Dependent Sebaceous Lipid Dysregulation UNKNOWN Altered differentiation is associated with divergent sebaceous states in comedonal and pustular lesions.
Lesion-Context-Dependent Sebaceous Lipid Dysregulation -> Follicular Retention Hyperkeratosis and Microcomedone Formation UNKNOWN Comedonal lesions show increased sebogenesis, but the direction and necessity of this relationship remain uncertain.
Follicular Retention Hyperkeratosis and Microcomedone Formation -> Comedones UNKNOWN Retention hyperkeratosis and microcomedone enlargement produce the clinically visible comedonal lesion.
Early and Sustained Pilosebaceous Inflammation -> Comedones UNKNOWN Subclinical inflammation may participate before visible comedones, but its causal role in comedogenesis remains uncertain.
Show evidence (2 references)
PMID:40689430 SUPPORT Other
"Both GWAS and single gene disorders unequivocally indicate stem/progenitor cell maintenance and cellular migration as the most important processes in the pathogenesis of acne."
A recent genetics synthesis proposes follicular lineage maintenance and migration as central mechanisms.
GEO:GSE301280 SUPPORT Human Clinical
"Both lesion types exhibit increased AP-1 transcription factors and elevated FABP5, a chaperone that blunts retinoic acid receptor signaling."
Human spatial data identify differentiation and retinoid-signaling abnormalities across lesion states.
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Discussions and Knowledge Gaps

1
How do follicular lineage state, sebaceous activity, microbial community structure, and inflammation vary across non-lesional skin, microcomedones, comedones, papules, and pustules, and which changes are causal initiators?
CONTROVERSY OPEN acne_pathogenic_ordering
Attached to
pathophysiology#Abnormal Pilosebaceous Differentiation pathophysiology#Lesion-Context-Dependent Sebaceous Lipid Dysregulation pathophysiology#C. acnes Community and Strain-Dependent Immune Signaling pathophysiology#Early and Sustained Pilosebaceous Inflammation
The traditional four-factor account remains clinically useful, but early inflammation, lesion-specific sebogenesis, strain-level microbiome effects, and new genetics all argue against a universal linear sequence from sebum through bacteria to inflammation. Cross-sectional tissue studies cannot establish temporal order. Longitudinal and paired spatial/single-cell sampling across lesion stages is needed to distinguish causes from responses.
Show evidence (3 references)
PMID:40689430 SUPPORT Other
"There are, however, several problems with this supposed sequence of events"
The genetics review explicitly challenges the conventional causal ordering.
GEO:GSE301280 SUPPORT Human Clinical
"comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
Lesion-state divergence argues against uniform sebaceous overproduction across acne.
PMID:24062871 SUPPORT Other
"evidence has emerged supporting a role for inflammation at all stages of acne lesion development, perhaps subclinically even before comedo formation"
Early inflammation makes a strictly late inflammatory stage implausible.
⚙

Pathophysiology

6
Abnormal Pilosebaceous Differentiation
Human spatial data and genetic synthesis implicate altered follicular stem/progenitor maintenance, keratinocyte migration, and sebocyte differentiation. These findings are mechanistically important but do not yet establish a single initiating lesion.
Follicular Stem/Progenitor and Differentiation Model
keratinocyte CL:0000312 sebocyte CL:0000317
pilosebaceous unit UBERON:0011932
Downstream
Follicular Retention Hyperkeratosis and Microcomedone Formation Follicular lineage and migration abnormalities may promote retention hyperkeratosis and microcomedone initiation. Follicular Stem/Progenitor and Differentiation Model
Lesion-Context-Dependent Sebaceous Lipid Dysregulation Altered differentiation is associated with divergent sebaceous states in comedonal and pustular lesions. Follicular Stem/Progenitor and Differentiation Model
Show evidence (2 references)
GEO:GSE301280 SUPPORT Human Clinical
"Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
Spatial profiling demonstrates lesion-state-specific pilosebaceous differentiation and sebogenesis.
PMID:40689430 PARTIAL Other
"Both GWAS and single gene disorders unequivocally indicate stem/progenitor cell maintenance and cellular migration as the most important processes in the pathogenesis of acne."
Genetic evidence supports a lineage-maintenance interpretation but does not define the full causal sequence.
Lesion-Context-Dependent Sebaceous Lipid Dysregulation
Androgen and IGF-1 signaling can increase sebaceous activity, while lipid composition and sebocyte differentiation also change. Sebogenesis is not uniformly elevated across all lesions: human spatial data show upregulation in comedonal skin and downregulation in pustular skin.
Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
sebocyte CL:0000317
lipid metabolic process GO:0006629
sebaceous gland UBERON:0001821
Downstream
Follicular Retention Hyperkeratosis and Microcomedone Formation Comedonal lesions show increased sebogenesis, but the direction and necessity of this relationship remain uncertain. Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
Show evidence (2 references)
GEO:GSE301280 SUPPORT Human Clinical
"Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
The dataset directly demonstrates lesion-dependent sebaceous transcriptional states.
PMID:32748305 PARTIAL Other
"Excess sebum production occurs because of increased activity of androgen hormones and IGF-1"
The review supports androgen/IGF-1-responsive sebaceous activity but not universal circulating androgen elevation.
Follicular Retention Hyperkeratosis and Microcomedone Formation
Abnormal follicular keratinocyte differentiation and desquamation retain keratin within the pilosebaceous unit and contribute to microcomedone and visible comedone formation.
Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
keratinocyte CL:0000312
keratinization GO:0031424
pilosebaceous unit UBERON:0011932
Downstream
Comedones Retention hyperkeratosis and microcomedone enlargement produce the clinically visible comedonal lesion. Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
Show evidence (1 reference)
PMID:32748305 SUPPORT Other
"Acne pathogenesis is attributed to four key factors: excess sebum production, hyperproliferation of Cutibacterium acnes (C. acnes, formerly called Propionibacterium acnes) bacteria, hyperkeratinization of the pilosebaceous follicles, and inflammatory mechanisms"
Follicular hyperkeratinization is a consistently recognized component of acne pathogenesis.
C. acnes Community and Strain-Dependent Immune Signaling
C. acnes is normal follicular flora rather than an infectious agent. Acne-associated phylotypes, reduced strain diversity, microbial-community imbalance, and host response may contribute to disease even when total bacterial abundance is similar in acne and unaffected skin.
Canonical Multifactorial Pilosebaceous Model
pilosebaceous unit UBERON:0011932
Downstream
Early and Sustained Pilosebaceous Inflammation Acne-associated strains can activate keratinocyte/sebocyte innate immune pathways through porphyrin, potassium-leakage, TLR2, and NLRP3 mechanisms. Canonical Multifactorial Pilosebaceous Model
Show evidence (2 references)
DOI:10.1007/s13555-023-01079-8 SUPPORT Other
"C. acnes represents a paradigm of a skin commensal bacterium residing in the human healthy skin that can also be etiologi-cally related to acne (e.g., a non-infectious, chronic inflammatory skin disease)."
The review directly distinguishes commensal contribution from infectious causation.
DOI:10.1007/s13555-023-01079-8 SUPPORT Other
"Distinct ‘ ‘acnegenic’ ’C. acnes phylotypes and a loss of C. acnes phylotype diversity are associated with acne"
Strain composition and diversity, rather than simple presence, are associated with acne.
Early and Sustained Pilosebaceous Inflammation
Innate and adaptive inflammation can be detected early, including before visible comedones, and persists through inflammatory lesion development. C. acnes-responsive TLR2/NLRP3 signaling is one contributor, not the sole obligatory inflammatory route.
Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
keratinocyte CL:0000312 sebocyte CL:0000317 neutrophil CL:0000775
inflammatory response GO:0006954
pilosebaceous unit UBERON:0011932
Downstream
Comedones Subclinical inflammation may participate before visible comedones, but its causal role in comedogenesis remains uncertain. Canonical Multifactorial Pilosebaceous Model Follicular Stem/Progenitor and Differentiation Model
Inflammatory papules Pilosebaceous inflammation produces a raised erythematous inflammatory lesion through tissue infiltration and edema. Canonical Multifactorial Pilosebaceous Model
Pustules Neutrophil recruitment into an inflamed follicular lesion produces pustular morphology. Canonical Multifactorial Pilosebaceous Model
Post-Inflammatory Hyperpigmentation Acne inflammation can stimulate melanogenesis and abnormal melanin deposition after active lesions without requiring deep follicular rupture. Canonical Multifactorial Pilosebaceous Model
Deep Follicular Inflammation, Rupture, and Repair Persistent or deep inflammation can disrupt the follicular wall and initiate dermal inflammatory repair. Canonical Multifactorial Pilosebaceous Model
Show evidence (2 references)
PMID:24820890 SUPPORT In Vitro
"After stimulation of human sebocytes with P. acnes, the activation of caspase-1 and secretion of IL-1β were enhanced significantly."
Human sebocyte experiments support C. acnes-responsive inflammasome signaling.
PMID:24062871 SUPPORT Other
"evidence has emerged supporting a role for inflammation at all stages of acne lesion development, perhaps subclinically even before comedo formation"
The review supports inflammation as an early and persistent feature rather than a purely late consequence.
Deep Follicular Inflammation, Rupture, and Repair
Severe follicular inflammation and wall disruption extend into the dermis. Subsequent extracellular-matrix injury and remodeling can leave permanent scars.
Canonical Multifactorial Pilosebaceous Model
inflammatory response GO:0006954
dermis UBERON:0002067
Downstream
Nodules and Cysts Deep inflammatory acne manifests clinically as nodular or cystic lesions. Canonical Multifactorial Pilosebaceous Model
Atrophic Acne Scarring Dermal injury and remodeling after inflammatory acne can produce permanent atrophic scars. Canonical Multifactorial Pilosebaceous Model
Show evidence (1 reference)
PMID:16092795 PARTIAL Other
"the differences highlighted in the inflammatory profiles of inflamed lesions from patients who scar, as compared with other nonscarring acne patients reinforces the view that acne is a disorder, which embraces a number of pathologies."
Distinct inflammatory profiles are associated with scar-forming lesions, while the detailed causal determinants remain uncertain.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Acne Vulgaris Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

6
Immune 3
Comedones Comedonal acne HP:0040137
Show evidence (1 reference)
PMID:40689430 SUPPORT Other
"It is characterized by the presence of comedones (blackheads), papules, and pustules."
The genetics review identifies comedones as a defining lesion morphology.
Pustules Pustule HP:0200039
Show evidence (1 reference)
PMID:40689430 SUPPORT Other
"It is characterized by the presence of comedones (blackheads), papules, and pustules."
Pustules are part of the characteristic acne lesion spectrum.
Nodules and Cysts Cystic acne HP:0033188
Show evidence (1 reference)
PMID:21062102 SUPPORT Other
"Severe nodular acne, defined as grade 4 or 5 acne on the Investigator's Static Global Assessment scale, is a skin condition characterized by intense erythema, inflammation, nodules, cysts, and scarring."
The review defines the nodular/cystic morphology of severe acne.
Integument 3
Inflammatory papules Erythematous papule HP:0030350
Show evidence (1 reference)
PMID:40689430 SUPPORT Other
"It is characterized by the presence of comedones (blackheads), papules, and pustules."
Papules are part of the characteristic acne lesion spectrum.
Post-Inflammatory Hyperpigmentation Hyperpigmentation of the skin HP:0000953
Show evidence (1 reference)
PMID:34468934 SUPPORT Other
"post-inflammatory hyperpigmentation is more common in darker skin"
The review directly identifies acne-associated hyperpigmentation and its greater prominence in darker skin.
Atrophic Acne Scarring Atrophic scars HP:0001075
Show evidence (1 reference)
PMID:29344322 SUPPORT Other
"This review focuses on atrophic scars, the most common type of acne scar."
The review identifies atrophic scars as the predominant acne-scar morphology.
💊

Medical Actions

8
Topical retinoids
Action: retinoid agent therapy Ontology label: Pharmacotherapy NCIT:C15986
Agent: retinoid CHEBI:26537
First-line comedolytic and anti-inflammatory therapy; examples include adapalene, tretinoin, tazarotene, and trifarotene. Irritation and pregnancy-related precautions depend on the specific agent.
Mechanism Target:
INHIBITS Follicular Retention Hyperkeratosis and Microcomedone Formation — Topical retinoids normalize keratinocyte differentiation and reduce hyperkeratinization.
Show evidence (1 reference)
PMID:36927117 SUPPORT Other
"Trifarotene, like other topical retinoids, acts by increasing keratinocyte differentiation and decreasing proliferation, which reduces hyperkeratinization."
The class mechanism directly supports inhibition of retention hyperkeratosis.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
The 2024 guideline strongly recommends topical retinoids.
Benzoyl peroxide
Action: antimicrobial agent therapy Ontology label: Pharmacotherapy NCIT:C15986
Agent: benzoyl peroxide NCIT:C47411
First-line non-antibiotic bactericidal therapy, often combined with a retinoid or antibiotic; it does not select bacterial resistance in the same way as antibiotics.
Mechanism Target:
INHIBITS C. acnes Community and Strain-Dependent Immune Signaling — Benzoyl peroxide reduces follicular C. acnes through a non-antibiotic bactericidal action.
Show evidence (1 reference)
DOI:10.1007/s13555-023-01079-8 SUPPORT Other
"BPO does not induce bacterial resistance and shows a well-established bactericidal non-an-tibiotic action."
The microbiome review directly supports the bactericidal, resistance-sparing mechanism.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
The 2024 guideline strongly recommends benzoyl peroxide.
Topical antibiotic combination therapy
Action: Antibiotic Therapy NCIT:C15620
Agent: antibiotic NCIT:C258
Topical antibiotics can reduce inflammatory acne but should not be used as monotherapy; combining them with benzoyl peroxide and other topical mechanisms limits resistance.
Show evidence (2 references)
PMID:38300170 SUPPORT Other
"Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
The guideline supports topical antibiotics as part of evidence-based acne therapy.
PMID:38300170 SUPPORT Other
"Combining topical therapies with multiple mechanisms of action, limiting systemic antibiotic use, combining systemic antibiotics with topical therapies"
The guideline supports multimodal topical therapy and antibiotic stewardship.
Oral doxycycline or related tetracyclines
Action: Antibiotic Therapy NCIT:C15620
Agent: doxycycline CHEBI:50845
Systemic tetracyclines are used with topical therapy for moderate-to-severe inflammatory acne. Duration should be limited, and concurrent benzoyl peroxide/topical therapy is used to reduce resistance risk.
Show evidence (2 references)
PMID:38300170 SUPPORT Other
"Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
The guideline strongly recommends oral doxycycline.
PMID:36568833 PARTIAL Other
"The overuse of topical and/or systemic antibiotics, the long treatment courses used for acne, and the availability of over-the-counter antibiotic preparations, have led to the worldwide emergence of resistant strains in acne patients."
The review supports limiting antibiotic exposure and using stewardship.
Oral isotretinoin
Action: retinoid agent therapy Ontology label: Pharmacotherapy NCIT:C15986
Agent: isotretinoin NCIT:C603
Systemic retinoid for severe acne, acne causing scarring or major psychosocial burden, or disease failing standard topical/oral therapy. It is highly teratogenic and requires risk-management and adverse-effect monitoring.
Mechanism Target:
INHIBITS Lesion-Context-Dependent Sebaceous Lipid Dysregulation — Isotretinoin strongly suppresses sebaceous-gland activity and sebum production.
Show evidence (1 reference)
PMID:20482692 SUPPORT Other
"Isotretinoin (13-cis retinoic acid) is the most potent known inhibitor of sebum production."
The review directly supports suppression of sebum production.
INHIBITS Follicular Retention Hyperkeratosis and Microcomedone Formation — Isotretinoin normalizes follicular keratinization.
Show evidence (1 reference)
PMID:20482692 SUPPORT Other
"normalization of the pattern of keratinization within the sebaceous gland follicle"
The source explicitly identifies normalization of follicular keratinization.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Oral isotretinoin is strongly recommended for acne that is severe, causing psychosocial burden or scarring, or failing standard oral or topical therapy."
The guideline defines the principal indications for oral isotretinoin.
Combined oral contraceptives
Action: combined oral contraceptive therapy Ontology label: Hormonal Contraception NCIT:C92808
Agent: oral contraceptive NCIT:C389
An option for appropriately selected patients with hormonally responsive acne, after individualized contraindication and risk assessment.
Mechanism Target:
MODULATES Lesion-Context-Dependent Sebaceous Lipid Dysregulation — Estrogen-containing contraceptives lower free androgen signaling, reducing androgen-responsive sebaceous activity.
Show evidence (1 reference)
PMID:28492054 SUPPORT Other
"Estrogen is known to stimulate the hepatic synthesis of sex hormone and bind globulin, which binds androgens and decreases levels of free testosterone"
Increased sex-hormone-binding globulin reduces free androgen exposure.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid, as well as for oral minocycline, sarecycline, combined oral contraceptive pills, and spironolactone."
The guideline conditionally recommends combined oral contraceptive pills.
Spironolactone
Action: Pharmacotherapy NCIT:C15986
Agent: spironolactone CHEBI:9241
An antiandrogen option for appropriately selected patients, particularly women with persistent or hormonally patterned acne; pregnancy and patient-specific contraindications must be considered.
Mechanism Target:
MODULATES Lesion-Context-Dependent Sebaceous Lipid Dysregulation — Spironolactone reduces androgen signaling through receptor and steroid-metabolism effects.
Show evidence (1 reference)
PMID:28492054 SUPPORT Other
"this agent also exhibits anti-androgen effects through inhibition of the cytochrome p450 system, inhibition of 5 alpha-reductase activity, and increase of hepatic synthesis of sex hormone-binding globulin"
The review directly describes spironolactone's antiandrogen mechanisms.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid, as well as for oral minocycline, sarecycline, combined oral contraceptive pills, and spironolactone."
The guideline conditionally recommends spironolactone.
Topical azelaic acid
Action: Pharmacotherapy NCIT:C15986
Agent: azelaic acid NCIT:C47407
A conditionally recommended topical option for inflammatory and comedonal acne, also useful when post-inflammatory pigmentary change is a concern.
Show evidence (1 reference)
PMID:38300170 SUPPORT Other
"Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid"
The guideline conditionally recommends azelaic acid for acne.
🌍

Environmental Factors

3
High-Glycemic-Load Diet
High glycemic load may modify acne severity through insulin/IGF-1-related signaling, but intervention evidence is limited and diet is not a necessary cause of acne.
Show evidence (2 references)
PMID:32748305 PARTIAL Other
"individuals with acne who consume diets with a low glycemic load have reduced acne lesions compared with individuals on high glycemic load diets."
Limited intervention evidence supports a glycemic-load effect on lesion counts.
PMID:23210645 REFUTE Other
"A systematic review in 2005 found no clear evidence of dietary components increasing acne risk."
Epidemiologic evidence has historically been insufficient for broad dietary causation claims.
Dairy Consumption
Dairy intake has observational associations with acne, and insulinotropic whey proteins are a proposed mechanism; heterogeneity and confounding leave the magnitude and causality uncertain.
Show evidence (2 references)
PMID:32748305 PARTIAL Other
"whey proteins responsible for the insulinotropic effects of milk may contribute more to acne development than the actual fat or dairy content."
The review presents an insulinotropic hypothesis rather than definitive causal evidence.
PMID:23210645 PARTIAL Other
"A possible association between dairy food intake and acne requires closer scrutiny."
The epidemiology review explicitly qualifies the dairy association as unresolved.
Psychological Stress
Psychological stress is associated with onset or exacerbation through incompletely resolved cutaneous neuroimmune pathways.
Show evidence (1 reference)
PMID:28871928 PARTIAL Other
"The basis for the association between emotional stress and the onset or exacerbation of acne is in several cutaneous neurogenic factors which interact with a pathogenic cascade in acne."
The review supports an association and neurogenic mechanisms but not a uniform causal effect.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Acne Vulgaris:

Rosacea MONDO:0006604
Overlapping Features Papulopustular rosacea can resemble facial inflammatory acne.
Distinguishing Features
  • Persistent central facial erythema, flushing, or telangiectasia favors rosacea.
  • Burning or stinging and ocular or phymatous features favor rosacea over acne.
Show evidence (1 reference)
PMID:28150107 SUPPORT Other
"Rosacea is a chronic facial inflammatory dermatosis characterized by flushing (or transient facial erythema), persistent central facial erythema, inflammatory papules/pustules, and telangiectasia."
The review provides the main rosacea features that distinguish it from acne.
Folliculitis MONDO:0006552
Overlapping Features Follicular papules or pustules, especially on the trunk or extremities, can resemble inflammatory acne.
Distinguishing Features
  • A predominantly truncal or extremity follicular pustular eruption warrants evaluation for folliculitis rather than assuming acne.
  • The complete lesion pattern and distribution, including whether comedones are present, guide clinical distinction.
Show evidence (1 reference)
PMID:12113648 PARTIAL Other
"Localized pustular eruptions are seen on the hands and feet in adults with pustulosis palmaris et plantaris and acrodermatitis continua (both of which may be variants of psoriasis); on the face in patients with acne vulgaris, rosacea, and perioral dermatitis; and on the trunk and/or extremities..."
The review documents overlapping pustular morphology with a distribution that can help distinguish folliculitis.
📊

Related Datasets

3
Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris geo:GSE301280
Targeted spatial transcriptomics of healthy, non-lesional, comedonal, and pustular human acne skin, focused on sebaceous differentiation, lipid metabolism, and retinoid signaling.
human SPATIAL TRANSCRIPTOMICS n=24
Conditions: healthy skin non-lesional acne skin comedonal acne skin pustular acne skin
This is targeted spatial profiling rather than unbiased whole-transcriptome sequencing.
Show evidence (1 reference)
GEO:GSE301280 SUPPORT Human Clinical
"Here, we performed spatial transcriptomics on healthy, non-lesional, comedonal, and pustular acne skin using a custom panel targeting sebaceous differentiation, lipid metabolism, and retinoid signaling pathways."
The GEO summary directly describes the disease-state spatial comparison.
Microbiome-Derived Indole-3-lactic Acid Attenuates Cutibacterium acnes-Induced Inflammation via the Aryl Hydrocarbon Receptor Pathway geo:GSE315350
Bulk RNA sequencing of primary human epidermal keratinocytes stimulated with C. acnes and treated with microbiome-derived tryptophan metabolites.
human BULK RNA SEQ n=18
Conditions: C. acnes stimulation indole-3-lactic acid treatment indole-3-propionic acid treatment
The GEO series contains the human keratinocyte RNA-seq; a linked mouse model belongs to the associated study, not this series.
Show evidence (1 reference)
GEO:GSE315350 SUPPORT In Vitro
"In vitro, ILA and IPA significantly suppressed C. acnes-driven inflammatory mediators, including TNF-α, IL-1β, and COX2, whereas IAA demonstrated limited ef-ficacy."
The dataset summary identifies the human keratinocyte inflammatory perturbation and transcriptional response.
High-Resolution Spatial Map of the Human Facial Sebaceous Gland Reveals Marker Genes and Decodes Sebocyte Differentiation [MERFISH] geo:GSE292394
Healthy human facial sebaceous-gland spatial and single-cell reference atlas used to interpret sebocyte differentiation; it is not an acne cohort.
human SPATIAL TRANSCRIPTOMICS n=1
Conditions: healthy facial skin
Show evidence (1 reference)
GEO:GSE292394 SUPPORT Human Clinical
"By integrating Stereo-seq spatial transcriptomics, single-cell RNA sequencing, and validation though MERFISH, we identified four distinct stages of sebocyte differentiation, each characterized by unique gene signatures."
The GEO summary establishes this as a human sebocyte-differentiation reference atlas.
{ }

Source YAML

click to show 
name: Acne Vulgaris
creation_date: '2026-01-23T23:13:39Z'
updated_date: '2026-07-19T00:00:00Z'
description: >-
  Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit,
  usually affecting the face and trunk, that produces comedones with variable
  papules, pustules, nodules, pigmentary sequelae, and scarring. The canonical
  model involves interacting follicular differentiation and keratinization,
  androgen-responsive sebaceous activity, Cutibacterium acnes community or
  strain-dependent immune signaling, and inflammation rather than a simple
  bacterial infection. Recent human genetics and spatial-transcriptomic data
  additionally prioritize follicular stem/progenitor maintenance, cellular
  migration, and lesion-state-specific sebaceous differentiation, so the
  ordering of the major processes remains incompletely resolved.
category: Complex
parents:
- Inflammatory skin disease
- Pilosebaceous unit disorder
disease_term:
  preferred_term: acne vulgaris
  term:
    id: MONDO:0011438
    label: acne
synonyms:
- Acne
prevalence:
- population: European adolescents and young adults aged 15-24 years
  measure_type: POINT_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 57800.0
  notes: >-
    Adjusted prevalence of self-reported acne in a cross-sectional online quota
    survey of 10,521 participants from seven European countries. This
    ascertainment is not directly comparable with modeled population estimates.
  evidence:
  - reference: PMID:28707712
    reference_title: "Acne prevalence and associations with lifestyle: a cross-sectional online survey of adolescents/young adults in 7 European countries."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The overall adjusted prevalence of self-reported acne was 57.8% (95% confidence interval 56.9% to 58.7%)."
    explanation: The survey provides a precise self-reported estimate for its sampled European age group.
- population: Global adolescents and young adults aged 10-24 years in 2021
  measure_type: POINT_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 9790.5
  notes: >-
    Age-standardized modeled estimate from Global Burden of Disease 2021 data;
    case definitions and modeling differ from questionnaire surveys.
  evidence:
  - reference: PMID:39271178
    reference_title: "Global, regional and national burdens of acne vulgaris in adolescents and young adults aged 10-24 years from 1990 to 2021: a trend analysis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: |-
      RESULTS: Globally, the age-standardized prevalence rate of acne vulgaris among
      adolescents and young adults increased from 8563.4 per 100 000 population [95%
      uncertainty interval (UI) 7343.5-9920.1] in 1990 to 9790.5 (95% UI 8420.9-11
      287.2) per 100 000 population in 2021, with an AAPC of 0.43 [95% confidence
      interval (CI) 0.41-0.46].
    explanation: The GBD analysis reports the exact 2021 age-standardized modeled rate.
- population: Young people
  measure_type: UNKNOWN
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 20000.0
  notes: >-
    Secondary-review estimate for moderate-to-severe acne, not prevalence of
    acne of any severity. The source does not state a geography or time window.
  evidence:
  - reference: PMID:23210645
    reference_title: "Epidemiology of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Moderate-to-severe acne affects around 20% of young people and severity correlates with pubertal maturity."
    explanation: The review provides a severity-specific occurrence estimate with an unstated temporal frame.
inheritance:
- name: Polygenic inheritance
  inheritance_term:
    preferred_term: Polygenic inheritance
    term:
      id: HP:0010982
      label: Polygenic inheritance
  description: >-
    Common acne has high familial heritability and a polygenic, multifactorial
    architecture. No single-gene Mendelian model explains acne vulgaris in the
    general population.
  evidence:
  - reference: PMID:37662507
    reference_title: "Genetic Variants Associated with Acne Vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The phenomenon is influenced by polygenic inheritance or can be ascribed to the interplay between multiple genes and environmental factors."
    explanation: The genetics review explicitly characterizes acne as polygenic and multifactorial.
  - reference: PMID:23210645
    reference_title: "Epidemiology of acne vulgaris."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "The heritability of acne is almost 80% in first-degree relatives."
    explanation: Familial epidemiology supports a substantial inherited component without identifying a Mendelian cause.
mechanistic_hypotheses:
- hypothesis_group_id: canonical_pilosebaceous_interaction
  hypothesis_label: Canonical Multifactorial Pilosebaceous Model
  status: CANONICAL
  description: >-
    Follicular keratinization, androgen-responsive sebaceous activity, microbial
    community or strain effects, and innate/adaptive inflammation interact to
    produce acne lesions. These processes need not occur in one invariant linear
    order.
  evidence:
  - reference: DOI:10.1007/s13555-023-01079-8
    reference_title: "The Microbiome and Acne: Perspectives for Treatment"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "C. acnes acts in interplay with three other major patho-genetic factors, namely androgen-dependent hyperseborrhea, follicular keratinocyte hyper-proliferation, and inflammation [ 10, 11]."
    explanation: The review describes the canonical factors as interacting contributors.
- hypothesis_group_id: follicular_lineage_dysregulation
  hypothesis_label: Follicular Stem/Progenitor and Differentiation Model
  status: EMERGING
  description: >-
    Polygenic susceptibility may primarily disturb follicular stem/progenitor
    maintenance, cell migration, and pilosebaceous differentiation, with
    keratinization, sebaceous-state changes, and inflammation emerging in
    lesion-specific combinations.
  evidence:
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Both GWAS and single gene disorders unequivocally indicate stem/progenitor cell maintenance and cellular migration as the most important processes in the pathogenesis of acne."
    explanation: A recent genetics synthesis proposes follicular lineage maintenance and migration as central mechanisms.
  - reference: GEO:GSE301280
    reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both lesion types exhibit increased AP-1 transcription factors and elevated FABP5, a chaperone that blunts retinoic acid receptor signaling."
    explanation: Human spatial data identify differentiation and retinoid-signaling abnormalities across lesion states.
pathophysiology:
- name: Abnormal Pilosebaceous Differentiation
  mechanism_confidence: PROVISIONAL
  description: >-
    Human spatial data and genetic synthesis implicate altered follicular
    stem/progenitor maintenance, keratinocyte migration, and sebocyte
    differentiation. These findings are mechanistically important but do not yet
    establish a single initiating lesion.
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: sebocyte
    term:
      id: CL:0000317
      label: sebocyte
  locations:
  - preferred_term: pilosebaceous unit
    term:
      id: UBERON:0011932
      label: pilosebaceous unit
  evidence:
  - reference: GEO:GSE301280
    reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
    explanation: Spatial profiling demonstrates lesion-state-specific pilosebaceous differentiation and sebogenesis.
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Both GWAS and single gene disorders unequivocally indicate stem/progenitor cell maintenance and cellular migration as the most important processes in the pathogenesis of acne."
    explanation: Genetic evidence supports a lineage-maintenance interpretation but does not define the full causal sequence.
  downstream:
  - target: Follicular Retention Hyperkeratosis and Microcomedone Formation
    description: Follicular lineage and migration abnormalities may promote retention hyperkeratosis and microcomedone initiation.
    hypothesis_groups:
    - follicular_lineage_dysregulation
    causal_link_type: UNKNOWN
    evidence:
    - reference: PMID:40689430
      reference_title: "The Genetics of Acne."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "Both GWAS and single gene disorders unequivocally indicate stem/progenitor cell maintenance and cellular migration as the most important processes in the pathogenesis of acne."
      explanation: The source prioritizes lineage maintenance and migration, but the specific intermediate path to microcomedones remains unresolved.
  - target: Lesion-Context-Dependent Sebaceous Lipid Dysregulation
    description: Altered differentiation is associated with divergent sebaceous states in comedonal and pustular lesions.
    hypothesis_groups:
    - follicular_lineage_dysregulation
    causal_link_type: UNKNOWN
    evidence:
    - reference: GEO:GSE301280
      reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
      explanation: Human spatial data connect altered sebocyte state with lesion-specific sebogenesis, without proving directionality.
- name: Lesion-Context-Dependent Sebaceous Lipid Dysregulation
  mechanism_confidence: PROVISIONAL
  description: >-
    Androgen and IGF-1 signaling can increase sebaceous activity, while lipid
    composition and sebocyte differentiation also change. Sebogenesis is not
    uniformly elevated across all lesions: human spatial data show upregulation
    in comedonal skin and downregulation in pustular skin.
  cell_types:
  - preferred_term: sebocyte
    term:
      id: CL:0000317
      label: sebocyte
  biological_processes:
  - preferred_term: lipid metabolic process
    term:
      id: GO:0006629
      label: lipid metabolic process
  locations:
  - preferred_term: sebaceous gland
    term:
      id: UBERON:0001821
      label: sebaceous gland
  evidence:
  - reference: GEO:GSE301280
    reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
    explanation: The dataset directly demonstrates lesion-dependent sebaceous transcriptional states.
  - reference: PMID:32748305
    reference_title: "Effects of Diet on Acne and Its Response to Treatment."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Excess sebum production occurs because of increased activity of androgen hormones and IGF-1"
    explanation: The review supports androgen/IGF-1-responsive sebaceous activity but not universal circulating androgen elevation.
  downstream:
  - target: Follicular Retention Hyperkeratosis and Microcomedone Formation
    description: Comedonal lesions show increased sebogenesis, but the direction and necessity of this relationship remain uncertain.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    - follicular_lineage_dysregulation
    causal_link_type: UNKNOWN
    evidence:
    - reference: GEO:GSE301280
      reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
      supports: PARTIAL
      evidence_source: HUMAN_CLINICAL
      snippet: "Our analyses identified a PPARG+ transitional basal cell state in sebocytes and revealed that comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
      explanation: Sebogenesis is associated with comedonal state, but this cross-sectional dataset does not establish causal order.
- name: Follicular Retention Hyperkeratosis and Microcomedone Formation
  mechanism_confidence: ESTABLISHED
  description: >-
    Abnormal follicular keratinocyte differentiation and desquamation retain
    keratin within the pilosebaceous unit and contribute to microcomedone and
    visible comedone formation.
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  locations:
  - preferred_term: pilosebaceous unit
    term:
      id: UBERON:0011932
      label: pilosebaceous unit
  biological_processes:
  - preferred_term: keratinization
    term:
      id: GO:0031424
      label: keratinization
  evidence:
  - reference: PMID:32748305
    reference_title: "Effects of Diet on Acne and Its Response to Treatment."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Acne pathogenesis is attributed to four key factors: excess sebum production, hyperproliferation of Cutibacterium acnes (C. acnes, formerly called Propionibacterium acnes) bacteria, hyperkeratinization of the pilosebaceous follicles, and inflammatory mechanisms"
    explanation: Follicular hyperkeratinization is a consistently recognized component of acne pathogenesis.
  downstream:
  - target: Comedones
    description: Retention hyperkeratosis and microcomedone enlargement produce the clinically visible comedonal lesion.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    - follicular_lineage_dysregulation
    causal_link_type: UNKNOWN
    evidence:
    - reference: PMID:40689430
      reference_title: "The Genetics of Acne."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "It is characterized by the presence of comedones (blackheads), papules, and pustules."
      explanation: Comedones are defining acne lesions, while the precise stepwise transition from microcomedone is not established by this source.
- name: C. acnes Community and Strain-Dependent Immune Signaling
  mechanism_confidence: PROVISIONAL
  description: >-
    C. acnes is normal follicular flora rather than an infectious agent.
    Acne-associated phylotypes, reduced strain diversity, microbial-community
    imbalance, and host response may contribute to disease even when total
    bacterial abundance is similar in acne and unaffected skin.
  locations:
  - preferred_term: pilosebaceous unit
    term:
      id: UBERON:0011932
      label: pilosebaceous unit
  evidence:
  - reference: DOI:10.1007/s13555-023-01079-8
    reference_title: "The Microbiome and Acne: Perspectives for Treatment"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "C. acnes represents a paradigm of a skin commensal bacterium residing in the human healthy skin that can also be etiologi-cally related to acne (e.g., a non-infectious, chronic inflammatory skin disease)."
    explanation: The review directly distinguishes commensal contribution from infectious causation.
  - reference: DOI:10.1007/s13555-023-01079-8
    reference_title: "The Microbiome and Acne: Perspectives for Treatment"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Distinct ‘ ‘acnegenic’ ’C. acnes phylotypes and a loss of C. acnes phylotype diversity are associated with acne"
    explanation: Strain composition and diversity, rather than simple presence, are associated with acne.
  downstream:
  - target: Early and Sustained Pilosebaceous Inflammation
    description: Acne-associated strains can activate keratinocyte/sebocyte innate immune pathways through porphyrin, potassium-leakage, TLR2, and NLRP3 mechanisms.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - strain-dependent porphyrin production
    - potassium leakage
    - NLRP3 inflammasome activation
    evidence:
    - reference: PMID:34151228
      reference_title: "Porphyrins produced by acneic Cutibacterium acnes strains activate the inflammasome by inducing K(+) leakage."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "An acneic C. acnes strain as well as its porphyrins activates NRLP3 inflammasome assembly, whereas this was not observed with a non-acneic strain."
      explanation: A strain-comparative co-culture study establishes a porphyrin-dependent route to inflammasome activation.
- name: Early and Sustained Pilosebaceous Inflammation
  mechanism_confidence: ESTABLISHED
  description: >-
    Innate and adaptive inflammation can be detected early, including before
    visible comedones, and persists through inflammatory lesion development.
    C. acnes-responsive TLR2/NLRP3 signaling is one contributor, not the sole
    obligatory inflammatory route.
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: sebocyte
    term:
      id: CL:0000317
      label: sebocyte
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  locations:
  - preferred_term: pilosebaceous unit
    term:
      id: UBERON:0011932
      label: pilosebaceous unit
  evidence:
  - reference: PMID:24820890
    reference_title: "Propionibacterium acnes activates the NLRP3 inflammasome in human sebocytes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "After stimulation of human sebocytes with P. acnes, the activation of caspase-1 and secretion of IL-1β were enhanced significantly."
    explanation: Human sebocyte experiments support C. acnes-responsive inflammasome signaling.
  - reference: PMID:24062871
    reference_title: "The role of inflammation in the pathology of acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "evidence has emerged supporting a role for inflammation at all stages of acne lesion development, perhaps subclinically even before comedo formation"
    explanation: The review supports inflammation as an early and persistent feature rather than a purely late consequence.
  downstream:
  - target: Comedones
    description: Subclinical inflammation may participate before visible comedones, but its causal role in comedogenesis remains uncertain.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    - follicular_lineage_dysregulation
    causal_link_type: UNKNOWN
    evidence:
    - reference: PMID:24062871
      reference_title: "The role of inflammation in the pathology of acne."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "evidence has emerged supporting a role for inflammation at all stages of acne lesion development, perhaps subclinically even before comedo formation"
      explanation: Temporal presence before comedones does not by itself establish direction of causation.
  - target: Inflammatory papules
    description: Pilosebaceous inflammation produces a raised erythematous inflammatory lesion through tissue infiltration and edema.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24062871
      reference_title: "The role of inflammation in the pathology of acne."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "the progression from a so-called noninflammatory comedo to an inflammatory papule, pustule, or nodule"
      explanation: The review links inflammation with papular progression, but omits the full tissue pathway.
  - target: Pustules
    description: Neutrophil recruitment into an inflamed follicular lesion produces pustular morphology.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - neutrophil recruitment
    evidence:
    - reference: PMID:24062871
      reference_title: "The role of inflammation in the pathology of acne."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "the progression from a so-called noninflammatory comedo to an inflammatory papule, pustule, or nodule"
      explanation: The review links inflammatory progression with pustules; the neutrophil intermediate is biologically established but not detailed in this quotation.
  - target: Post-Inflammatory Hyperpigmentation
    description: Acne inflammation can stimulate melanogenesis and abnormal melanin deposition after active lesions without requiring deep follicular rupture.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - excess melanogenesis
    - abnormal melanin deposition
    evidence:
    - reference: PMID:34468934
      reference_title: "The Pathogenesis and Management of Acne-Induced Post-inflammatory Hyperpigmentation."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "the inflammatory processes of acne stimulate excess melanogenesis and abnormal melanin deposition, leading to pigmentary sequelae known as post-inflammatory hyperpigmentation"
      explanation: The source directly supports inflammation-driven pigmentary sequelae without making deep rupture a prerequisite.
  - target: Deep Follicular Inflammation, Rupture, and Repair
    description: Persistent or deep inflammation can disrupt the follicular wall and initiate dermal inflammatory repair.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16092795
      reference_title: "The role of inflammation in the pathogenesis of acne and acne scarring."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "Evidence now supports a pivotal role for cellular inflammatory events at all stages of acne lesion development, from preclinical initiation to clinical presentation of active lesions through to resolution."
      explanation: Inflammation spans lesion evolution and resolution, but the specific rupture sequence is incompletely resolved.
- name: Deep Follicular Inflammation, Rupture, and Repair
  mechanism_confidence: PROVISIONAL
  description: >-
    Severe follicular inflammation and wall disruption extend into the dermis.
    Subsequent extracellular-matrix injury and remodeling can leave permanent
    scars.
  locations:
  - preferred_term: dermis
    term:
      id: UBERON:0002067
      label: dermis
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  evidence:
  - reference: PMID:16092795
    reference_title: "The role of inflammation in the pathogenesis of acne and acne scarring."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "the differences highlighted in the inflammatory profiles of inflamed lesions from patients who scar, as compared with other nonscarring acne patients reinforces the view that acne is a disorder, which embraces a number of pathologies."
    explanation: Distinct inflammatory profiles are associated with scar-forming lesions, while the detailed causal determinants remain uncertain.
  downstream:
  - target: Nodules and Cysts
    description: Deep inflammatory acne manifests clinically as nodular or cystic lesions.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: UNKNOWN
    evidence:
    - reference: PMID:21062102
      reference_title: "Therapeutic considerations for severe nodular acne."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Severe nodular acne, defined as grade 4 or 5 acne on the Investigator's Static Global Assessment scale, is a skin condition characterized by intense erythema, inflammation, nodules, cysts, and scarring."
      explanation: Severe inflammatory acne co-occurs with nodules and cysts, but this clinical description does not prove a single causal route.
  - target: Atrophic Acne Scarring
    description: Dermal injury and remodeling after inflammatory acne can produce permanent atrophic scars.
    hypothesis_groups:
    - canonical_pilosebaceous_interaction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16092795
      reference_title: "The role of inflammation in the pathogenesis of acne and acne scarring."
      supports: PARTIAL
      evidence_source: OTHER
      snippet: "the differences highlighted in the inflammatory profiles of inflamed lesions from patients who scar, as compared with other nonscarring acne patients"
      explanation: The review supports an inflammation-scarring relationship but not a fully resolved remodeling pathway.
phenotypes:
- name: Comedones
  description: Open comedones (blackheads) and closed comedones (whiteheads) are characteristic non-inflammatory-appearing follicular lesions.
  phenotype_term:
    preferred_term: comedonal acne
    term:
      id: HP:0040137
      label: Comedonal acne
  evidence:
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is characterized by the presence of comedones (blackheads), papules, and pustules."
    explanation: The genetics review identifies comedones as a defining lesion morphology.
- name: Inflammatory papules
  description: Raised erythematous lesions caused by inflammation within and around the pilosebaceous unit.
  phenotype_term:
    preferred_term: erythematous papule
    term:
      id: HP:0030350
      label: Erythematous papule
  evidence:
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is characterized by the presence of comedones (blackheads), papules, and pustules."
    explanation: Papules are part of the characteristic acne lesion spectrum.
- name: Pustules
  description: Inflamed follicular lesions containing purulent material.
  phenotype_term:
    preferred_term: pustule
    term:
      id: HP:0200039
      label: Pustule
  evidence:
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is characterized by the presence of comedones (blackheads), papules, and pustules."
    explanation: Pustules are part of the characteristic acne lesion spectrum.
- name: Nodules and Cysts
  description: Deep, painful inflammatory lesions associated with severe acne and increased scarring risk.
  phenotype_term:
    preferred_term: cystic acne
    term:
      id: HP:0033188
      label: Cystic acne
  evidence:
  - reference: PMID:21062102
    reference_title: "Therapeutic considerations for severe nodular acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Severe nodular acne, defined as grade 4 or 5 acne on the Investigator's Static Global Assessment scale, is a skin condition characterized by intense erythema, inflammation, nodules, cysts, and scarring."
    explanation: The review defines the nodular/cystic morphology of severe acne.
- name: Post-Inflammatory Hyperpigmentation
  description: Persistent darkening at sites of resolved acne lesions, particularly prominent in darker skin phototypes.
  phenotype_term:
    preferred_term: hyperpigmentation of the skin
    term:
      id: HP:0000953
      label: Hyperpigmentation of the skin
  evidence:
  - reference: PMID:34468934
    reference_title: "The Pathogenesis and Management of Acne-Induced Post-inflammatory Hyperpigmentation."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "post-inflammatory hyperpigmentation is more common in darker skin"
    explanation: The review directly identifies acne-associated hyperpigmentation and its greater prominence in darker skin.
- name: Atrophic Acne Scarring
  description: Permanent depressed scars, including ice-pick, boxcar, and rolling morphologies, after inflammatory acne.
  phenotype_term:
    preferred_term: atrophic scars
    term:
      id: HP:0001075
      label: Atrophic scars
  evidence:
  - reference: PMID:29344322
    reference_title: "Acne Scarring-Pathogenesis, Evaluation, and Treatment Options."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This review focuses on atrophic scars, the most common type of acne scar."
    explanation: The review identifies atrophic scars as the predominant acne-scar morphology.
environmental:
- name: High-Glycemic-Load Diet
  description: >-
    High glycemic load may modify acne severity through insulin/IGF-1-related
    signaling, but intervention evidence is limited and diet is not a necessary
    cause of acne.
  effect: Possible modifier of lesion burden
  evidence:
  - reference: PMID:32748305
    reference_title: "Effects of Diet on Acne and Its Response to Treatment."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "individuals with acne who consume diets with a low glycemic load have reduced acne lesions compared with individuals on high glycemic load diets."
    explanation: Limited intervention evidence supports a glycemic-load effect on lesion counts.
  - reference: PMID:23210645
    reference_title: "Epidemiology of acne vulgaris."
    supports: REFUTE
    evidence_source: OTHER
    snippet: "A systematic review in 2005 found no clear evidence of dietary components increasing acne risk."
    explanation: Epidemiologic evidence has historically been insufficient for broad dietary causation claims.
- name: Dairy Consumption
  description: >-
    Dairy intake has observational associations with acne, and insulinotropic
    whey proteins are a proposed mechanism; heterogeneity and confounding leave
    the magnitude and causality uncertain.
  effect: Possible modifier of acne risk or severity
  evidence:
  - reference: PMID:32748305
    reference_title: "Effects of Diet on Acne and Its Response to Treatment."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "whey proteins responsible for the insulinotropic effects of milk may contribute more to acne development than the actual fat or dairy content."
    explanation: The review presents an insulinotropic hypothesis rather than definitive causal evidence.
  - reference: PMID:23210645
    reference_title: "Epidemiology of acne vulgaris."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "A possible association between dairy food intake and acne requires closer scrutiny."
    explanation: The epidemiology review explicitly qualifies the dairy association as unresolved.
- name: Psychological Stress
  description: Psychological stress is associated with onset or exacerbation through incompletely resolved cutaneous neuroimmune pathways.
  effect: Possible exacerbating factor
  evidence:
  - reference: PMID:28871928
    reference_title: "The Impact of Pyschological Stress on Acne."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "The basis for the association between emotional stress and the onset or exacerbation of acne is in several cutaneous neurogenic factors which interact with a pathogenic cascade in acne."
    explanation: The review supports an association and neurogenic mechanisms but not a uniform causal effect.
datasets:
- accession: geo:GSE301280
  title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
  description: >-
    Targeted spatial transcriptomics of healthy, non-lesional, comedonal, and
    pustular human acne skin, focused on sebaceous differentiation, lipid
    metabolism, and retinoid signaling.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: SPATIAL_TRANSCRIPTOMICS
  sample_count: 24
  conditions:
  - healthy skin
  - non-lesional acne skin
  - comedonal acne skin
  - pustular acne skin
  evidence:
  - reference: GEO:GSE301280
    reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we performed spatial transcriptomics on healthy, non-lesional, comedonal, and pustular acne skin using a custom panel targeting sebaceous differentiation, lipid metabolism, and retinoid signaling pathways."
    explanation: The GEO summary directly describes the disease-state spatial comparison.
  notes: This is targeted spatial profiling rather than unbiased whole-transcriptome sequencing.
- accession: geo:GSE315350
  title: "Microbiome-Derived Indole-3-lactic Acid Attenuates Cutibacterium acnes-Induced Inflammation via the Aryl Hydrocarbon Receptor Pathway"
  description: >-
    Bulk RNA sequencing of primary human epidermal keratinocytes stimulated with
    C. acnes and treated with microbiome-derived tryptophan metabolites.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 18
  conditions:
  - C. acnes stimulation
  - indole-3-lactic acid treatment
  - indole-3-propionic acid treatment
  evidence:
  - reference: GEO:GSE315350
    reference_title: "Microbiome-Derived Indole-3-lactic Acid Attenuates Cutibacterium acnes–Induced Inflammation via the Aryl Hydrocarbon Receptor Pathway"
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In vitro, ILA and IPA significantly suppressed C. acnes-driven inflammatory mediators, including TNF-α, IL-1β, and COX2, whereas IAA demonstrated limited ef-ficacy."
    explanation: The dataset summary identifies the human keratinocyte inflammatory perturbation and transcriptional response.
  notes: The GEO series contains the human keratinocyte RNA-seq; a linked mouse model belongs to the associated study, not this series.
- accession: geo:GSE292394
  title: "High-Resolution Spatial Map of the Human Facial Sebaceous Gland Reveals Marker Genes and Decodes Sebocyte Differentiation [MERFISH]"
  description: >-
    Healthy human facial sebaceous-gland spatial and single-cell reference atlas
    used to interpret sebocyte differentiation; it is not an acne cohort.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: SPATIAL_TRANSCRIPTOMICS
  sample_count: 1
  conditions:
  - healthy facial skin
  evidence:
  - reference: GEO:GSE292394
    reference_title: "High-Resolution Spatial Map of the Human Facial Sebaceous Gland Reveals Marker Genes and Decodes Sebocyte Differentiation [MERFISH]"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "By integrating Stereo-seq spatial transcriptomics, single-cell RNA sequencing, and validation though MERFISH, we identified four distinct stages of sebocyte differentiation, each characterized by unique gene signatures."
    explanation: The GEO summary establishes this as a human sebocyte-differentiation reference atlas.
diagnosis:
- name: Clinical lesion-pattern and severity assessment
  description: >-
    Diagnosis is usually clinical, based on comedonal, inflammatory, mixed, or
    nodulocystic morphology; face and/or trunk distribution; and severity,
    scarring, erythema, or hyperpigmentation. Most patients do not need routine
    laboratory or microbiologic testing, although selected presentations may
    warrant additional evaluation.
  evidence:
  - reference: PMID:34812859
    reference_title: "Management of Acne Vulgaris: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Acne vulgaris is classified based on patient age, lesion morphology (comedonal, inflammatory, mixed, nodulocystic), distribution (location on face, trunk, or both), and severity (extent, presence or absence of scarring, postinflammatory erythema, or hyperpigmentation)."
    explanation: The review describes the clinical dimensions used to recognize and classify acne.
  - reference: PMID:34812859
    reference_title: "Management of Acne Vulgaris: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although most acne does not require specific medical evaluation, medical workup is sometimes warranted."
    explanation: Routine testing is unnecessary for typical acne, with targeted workup reserved for selected cases.
treatments:
- name: Topical retinoids
  description: >-
    First-line comedolytic and anti-inflammatory therapy; examples include
    adapalene, tretinoin, tazarotene, and trifarotene. Irritation and
    pregnancy-related precautions depend on the specific agent.
  treatment_term:
    preferred_term: retinoid agent therapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: retinoid
      term:
        id: CHEBI:26537
        label: retinoid
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
    explanation: The 2024 guideline strongly recommends topical retinoids.
  target_mechanisms:
  - target: Follicular Retention Hyperkeratosis and Microcomedone Formation
    treatment_effect: INHIBITS
    description: Topical retinoids normalize keratinocyte differentiation and reduce hyperkeratinization.
    evidence:
    - reference: PMID:36927117
      reference_title: "Management of Acne Vulgaris With Trifarotene."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Trifarotene, like other topical retinoids, acts by increasing keratinocyte differentiation and decreasing proliferation, which reduces hyperkeratinization."
      explanation: The class mechanism directly supports inhibition of retention hyperkeratosis.
- name: Benzoyl peroxide
  description: >-
    First-line non-antibiotic bactericidal therapy, often combined with a
    retinoid or antibiotic; it does not select bacterial resistance in the same
    way as antibiotics.
  treatment_term:
    preferred_term: antimicrobial agent therapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: benzoyl peroxide
      term:
        id: NCIT:C47411
        label: Benzoyl Peroxide
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
    explanation: The 2024 guideline strongly recommends benzoyl peroxide.
  target_mechanisms:
  - target: C. acnes Community and Strain-Dependent Immune Signaling
    treatment_effect: INHIBITS
    description: Benzoyl peroxide reduces follicular C. acnes through a non-antibiotic bactericidal action.
    evidence:
    - reference: DOI:10.1007/s13555-023-01079-8
      reference_title: "The Microbiome and Acne: Perspectives for Treatment"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "BPO does not induce bacterial resistance and shows a well-established bactericidal non-an-tibiotic action."
      explanation: The microbiome review directly supports the bactericidal, resistance-sparing mechanism.
- name: Topical antibiotic combination therapy
  description: >-
    Topical antibiotics can reduce inflammatory acne but should not be used as
    monotherapy; combining them with benzoyl peroxide and other topical
    mechanisms limits resistance.
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
    therapeutic_agent:
    - preferred_term: antibiotic
      term:
        id: NCIT:C258
        label: Antibiotic
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
    explanation: The guideline supports topical antibiotics as part of evidence-based acne therapy.
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Combining topical therapies with multiple mechanisms of action, limiting systemic antibiotic use, combining systemic antibiotics with topical therapies"
    explanation: The guideline supports multimodal topical therapy and antibiotic stewardship.
- name: Oral doxycycline or related tetracyclines
  description: >-
    Systemic tetracyclines are used with topical therapy for moderate-to-severe
    inflammatory acne. Duration should be limited, and concurrent benzoyl
    peroxide/topical therapy is used to reduce resistance risk.
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
    therapeutic_agent:
    - preferred_term: doxycycline
      term:
        id: CHEBI:50845
        label: doxycycline
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Strong recommendations are made for benzoyl peroxide, topical retinoids, topical antibiotics, and oral doxycycline."
    explanation: The guideline strongly recommends oral doxycycline.
  - reference: PMID:36568833
    reference_title: "Antibiotics and Antimicrobial Resistance in Acne: Epidemiological Trends and Clinical Practice Considerations."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "The overuse of topical and/or systemic antibiotics, the long treatment courses used for acne, and the availability of over-the-counter antibiotic preparations, have led to the worldwide emergence of resistant strains in acne patients."
    explanation: The review supports limiting antibiotic exposure and using stewardship.
- name: Oral isotretinoin
  description: >-
    Systemic retinoid for severe acne, acne causing scarring or major
    psychosocial burden, or disease failing standard topical/oral therapy. It is
    highly teratogenic and requires risk-management and adverse-effect
    monitoring.
  treatment_term:
    preferred_term: retinoid agent therapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: isotretinoin
      term:
        id: NCIT:C603
        label: Isotretinoin
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Oral isotretinoin is strongly recommended for acne that is severe, causing psychosocial burden or scarring, or failing standard oral or topical therapy."
    explanation: The guideline defines the principal indications for oral isotretinoin.
  target_mechanisms:
  - target: Lesion-Context-Dependent Sebaceous Lipid Dysregulation
    treatment_effect: INHIBITS
    description: Isotretinoin strongly suppresses sebaceous-gland activity and sebum production.
    evidence:
    - reference: PMID:20482692
      reference_title: "Isotretinoin: state of the art treatment for acne vulgaris."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Isotretinoin (13-cis retinoic acid) is the most potent known inhibitor of sebum production."
      explanation: The review directly supports suppression of sebum production.
  - target: Follicular Retention Hyperkeratosis and Microcomedone Formation
    treatment_effect: INHIBITS
    description: Isotretinoin normalizes follicular keratinization.
    evidence:
    - reference: PMID:20482692
      reference_title: "Isotretinoin: state of the art treatment for acne vulgaris."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "normalization of the pattern of keratinization within the sebaceous gland follicle"
      explanation: The source explicitly identifies normalization of follicular keratinization.
- name: Combined oral contraceptives
  description: An option for appropriately selected patients with hormonally responsive acne, after individualized contraindication and risk assessment.
  treatment_term:
    preferred_term: combined oral contraceptive therapy
    term:
      id: NCIT:C92808
      label: Hormonal Contraception
    therapeutic_agent:
    - preferred_term: oral contraceptive
      term:
        id: NCIT:C389
        label: Oral Contraceptive
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid, as well as for oral minocycline, sarecycline, combined oral contraceptive pills, and spironolactone."
    explanation: The guideline conditionally recommends combined oral contraceptive pills.
  target_mechanisms:
  - target: Lesion-Context-Dependent Sebaceous Lipid Dysregulation
    treatment_effect: MODULATES
    description: Estrogen-containing contraceptives lower free androgen signaling, reducing androgen-responsive sebaceous activity.
    evidence:
    - reference: PMID:28492054
      reference_title: "A Review of hormone-based therapies to treat adult acne vulgaris in women."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Estrogen is known to stimulate the hepatic synthesis of sex hormone and bind globulin, which binds androgens and decreases levels of free testosterone"
      explanation: Increased sex-hormone-binding globulin reduces free androgen exposure.
- name: Spironolactone
  description: >-
    An antiandrogen option for appropriately selected patients, particularly
    women with persistent or hormonally patterned acne; pregnancy and
    patient-specific contraindications must be considered.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: spironolactone
      term:
        id: CHEBI:9241
        label: spironolactone
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid, as well as for oral minocycline, sarecycline, combined oral contraceptive pills, and spironolactone."
    explanation: The guideline conditionally recommends spironolactone.
  target_mechanisms:
  - target: Lesion-Context-Dependent Sebaceous Lipid Dysregulation
    treatment_effect: MODULATES
    description: Spironolactone reduces androgen signaling through receptor and steroid-metabolism effects.
    evidence:
    - reference: PMID:28492054
      reference_title: "A Review of hormone-based therapies to treat adult acne vulgaris in women."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "this agent also exhibits anti-androgen effects through inhibition of the cytochrome p450 system, inhibition of 5 alpha-reductase activity, and increase of hepatic synthesis of sex hormone-binding globulin"
      explanation: The review directly describes spironolactone's antiandrogen mechanisms.
- name: Topical azelaic acid
  description: A conditionally recommended topical option for inflammatory and comedonal acne, also useful when post-inflammatory pigmentary change is a concern.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: azelaic acid
      term:
        id: NCIT:C47407
        label: Azelaic Acid
  evidence:
  - reference: PMID:38300170
    reference_title: "Guidelines of care for the management of acne vulgaris."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Conditional recommendations are made for topical clascoterone, salicylic acid, and azelaic acid"
    explanation: The guideline conditionally recommends azelaic acid for acne.
differential_diagnoses:
- name: Rosacea
  disease_term:
    preferred_term: rosacea
    term:
      id: MONDO:0006604
      label: rosacea
  description: Papulopustular rosacea can resemble facial inflammatory acne.
  distinguishing_features:
  - Persistent central facial erythema, flushing, or telangiectasia favors rosacea.
  - Burning or stinging and ocular or phymatous features favor rosacea over acne.
  evidence:
  - reference: PMID:28150107
    reference_title: "Acne and Rosacea."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Rosacea is a chronic facial inflammatory dermatosis characterized by flushing (or transient facial erythema), persistent central facial erythema, inflammatory papules/pustules, and telangiectasia."
    explanation: The review provides the main rosacea features that distinguish it from acne.
- name: Folliculitis
  disease_term:
    preferred_term: folliculitis
    term:
      id: MONDO:0006552
      label: folliculitis
  description: Follicular papules or pustules, especially on the trunk or extremities, can resemble inflammatory acne.
  distinguishing_features:
  - A predominantly truncal or extremity follicular pustular eruption warrants evaluation for folliculitis rather than assuming acne.
  - The complete lesion pattern and distribution, including whether comedones are present, guide clinical distinction.
  evidence:
  - reference: PMID:12113648
    reference_title: "Pustular skin disorders: diagnosis and treatment."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Localized pustular eruptions are seen on the hands and feet in adults with pustulosis palmaris et plantaris and acrodermatitis continua (both of which may be variants of psoriasis); on the face in patients with acne vulgaris, rosacea, and perioral dermatitis; and on the trunk and/or extremities in patients with folliculitis."
    explanation: The review documents overlapping pustular morphology with a distribution that can help distinguish folliculitis.
discussions:
- discussion_id: acne_pathogenic_ordering
  prompt: >-
    How do follicular lineage state, sebaceous activity, microbial community
    structure, and inflammation vary across non-lesional skin, microcomedones,
    comedones, papules, and pustules, and which changes are causal initiators?
  kind: CONTROVERSY
  status: OPEN
  attaches_to:
  - pathophysiology#Abnormal Pilosebaceous Differentiation
  - pathophysiology#Lesion-Context-Dependent Sebaceous Lipid Dysregulation
  - pathophysiology#C. acnes Community and Strain-Dependent Immune Signaling
  - pathophysiology#Early and Sustained Pilosebaceous Inflammation
  rationale: >-
    The traditional four-factor account remains clinically useful, but early
    inflammation, lesion-specific sebogenesis, strain-level microbiome effects,
    and new genetics all argue against a universal linear sequence from sebum
    through bacteria to inflammation. Cross-sectional tissue studies cannot establish
    temporal order. Longitudinal and paired spatial/single-cell sampling across
    lesion stages is needed to distinguish causes from responses.
  evidence:
  - reference: PMID:40689430
    reference_title: "The Genetics of Acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "There are, however, several problems with this supposed sequence of events"
    explanation: The genetics review explicitly challenges the conventional causal ordering.
  - reference: GEO:GSE301280
    reference_title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "comedonal skin upregulates sebogenesis genes, whereas pustular skin downregulates sebogenesis."
    explanation: Lesion-state divergence argues against uniform sebaceous overproduction across acne.
  - reference: PMID:24062871
    reference_title: "The role of inflammation in the pathology of acne."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "evidence has emerged supporting a role for inflammation at all stages of acne lesion development, perhaps subclinically even before comedo formation"
    explanation: Early inflammation makes a strictly late inflammatory stage implausible.
notes: |
  Acne vulgaris is modeled as non-infectious; C. acnes is retained only as a
  commensal, community- and strain-dependent mechanistic contributor. Small,
  ancestry-limited candidate-polymorphism studies are not promoted to causal or
  susceptibility-gene assertions because replication is insufficient. The
  treatment list emphasizes evidence-based pharmacologic care from the 2024 AAD
  guideline; isolated peels, light/laser devices, photodynamic therapy,
  platelet-rich plasma, and post-procedure recovery products were removed rather
  than exported as established treatments of acne. The European self-report and global
  burden estimates are not interchangeable with self-reported online survey
  prevalence because ascertainment and case definitions differ.
references:
- reference: PMID:12113648
  title: "Pustular skin disorders: diagnosis and treatment."
  findings: []
- reference: PMID:16092795
  title: "The role of inflammation in the pathogenesis of acne and acne scarring."
  findings: []
- reference: PMID:20482692
  title: "Isotretinoin: state of the art treatment for acne vulgaris."
  findings: []
- reference: PMID:21062102
  title: "Therapeutic considerations for severe nodular acne."
  findings: []
- reference: PMID:23210645
  title: "Epidemiology of acne vulgaris."
  findings: []
- reference: PMID:24062871
  title: "The role of inflammation in the pathology of acne."
  findings: []
- reference: PMID:24820890
  title: "Propionibacterium acnes activates the NLRP3 inflammasome in human sebocytes."
  findings: []
- reference: PMID:28150107
  title: "Acne and Rosacea."
  findings: []
- reference: PMID:28492054
  title: "A Review of hormone-based therapies to treat adult acne vulgaris in women."
  findings: []
- reference: PMID:28707712
  title: "Acne prevalence and associations with lifestyle: a cross-sectional online survey of adolescents/young adults in 7 European countries."
  findings: []
- reference: PMID:28871928
  title: "The Impact of Pyschological Stress on Acne."
  findings: []
- reference: PMID:29344322
  title: "Acne Scarring-Pathogenesis, Evaluation, and Treatment Options."
  findings: []
- reference: PMID:32748305
  title: "Effects of Diet on Acne and Its Response to Treatment."
  findings: []
- reference: PMID:34151228
  title: "Porphyrins produced by acneic Cutibacterium acnes strains activate the inflammasome by inducing K(+) leakage."
  findings: []
- reference: PMID:34468934
  title: "The Pathogenesis and Management of Acne-Induced Post-inflammatory Hyperpigmentation."
  findings: []
- reference: PMID:34812859
  title: "Management of Acne Vulgaris: A Review."
  findings: []
- reference: PMID:36568833
  title: "Antibiotics and Antimicrobial Resistance in Acne: Epidemiological Trends and Clinical Practice Considerations."
  findings: []
- reference: PMID:36927117
  title: "Management of Acne Vulgaris With Trifarotene."
  findings: []
- reference: PMID:37662507
  title: "Genetic Variants Associated with Acne Vulgaris."
  findings: []
- reference: PMID:38300170
  title: "Guidelines of care for the management of acne vulgaris."
  findings: []
- reference: PMID:39271178
  title: "Global, regional and national burdens of acne vulgaris in adolescents and young adults aged 10-24 years from 1990 to 2021: a trend analysis."
  findings: []
- reference: PMID:40689430
  title: "The Genetics of Acne."
  findings: []
- reference: DOI:10.1007/s13555-023-01079-8
  title: "The Microbiome and Acne: Perspectives for Treatment"
  findings: []
- reference: GEO:GSE301280
  title: "Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris"
  findings: []
- reference: GEO:GSE315350
  title: "Microbiome-Derived Indole-3-lactic Acid Attenuates Cutibacterium acnes–Induced Inflammation via the Aryl Hydrocarbon Receptor Pathway"
  findings: []
- reference: GEO:GSE292394
  title: "High-Resolution Spatial Map of the Human Facial Sebaceous Gland Reveals Marker Genes and Decodes Sebocyte Differentiation [MERFISH]"
  findings: []
📚

References & Deep Research

References

26
PMID:12113648
Pustular skin disorders: diagnosis and treatment.
No top-level findings curated for this source.
PMID:16092795
The role of inflammation in the pathogenesis of acne and acne scarring.
No top-level findings curated for this source.
PMID:20482692
Isotretinoin: state of the art treatment for acne vulgaris.
No top-level findings curated for this source.
PMID:21062102
Therapeutic considerations for severe nodular acne.
No top-level findings curated for this source.
PMID:23210645
Epidemiology of acne vulgaris.
No top-level findings curated for this source.
PMID:24062871
The role of inflammation in the pathology of acne.
No top-level findings curated for this source.
PMID:24820890
Propionibacterium acnes activates the NLRP3 inflammasome in human sebocytes.
No top-level findings curated for this source.
PMID:28150107
Acne and Rosacea.
No top-level findings curated for this source.
PMID:28492054
A Review of hormone-based therapies to treat adult acne vulgaris in women.
No top-level findings curated for this source.
PMID:28707712
Acne prevalence and associations with lifestyle: a cross-sectional online survey of adolescents/young adults in 7 European countries.
No top-level findings curated for this source.
PMID:28871928
The Impact of Pyschological Stress on Acne.
No top-level findings curated for this source.
PMID:29344322
Acne Scarring-Pathogenesis, Evaluation, and Treatment Options.
No top-level findings curated for this source.
PMID:32748305
Effects of Diet on Acne and Its Response to Treatment.
No top-level findings curated for this source.
PMID:34151228
Porphyrins produced by acneic Cutibacterium acnes strains activate the inflammasome by inducing K(+) leakage.
No top-level findings curated for this source.
PMID:34468934
The Pathogenesis and Management of Acne-Induced Post-inflammatory Hyperpigmentation.
No top-level findings curated for this source.
PMID:34812859
Management of Acne Vulgaris: A Review.
No top-level findings curated for this source.
PMID:36568833
Antibiotics and Antimicrobial Resistance in Acne: Epidemiological Trends and Clinical Practice Considerations.
No top-level findings curated for this source.
PMID:36927117
Management of Acne Vulgaris With Trifarotene.
No top-level findings curated for this source.
PMID:37662507
Genetic Variants Associated with Acne Vulgaris.
No top-level findings curated for this source.
PMID:38300170
Guidelines of care for the management of acne vulgaris.
No top-level findings curated for this source.
PMID:39271178
Global, regional and national burdens of acne vulgaris in adolescents and young adults aged 10-24 years from 1990 to 2021: a trend analysis.
No top-level findings curated for this source.
PMID:40689430
The Genetics of Acne.
No top-level findings curated for this source.
DOI:10.1007/s13555-023-01079-8
The Microbiome and Acne: Perspectives for Treatment
No top-level findings curated for this source.
GEO:GSE301280
Spatial transcriptomics reveals dysfunctional lipid metabolism and abnormal pilosebaceous differentiation in acne vulgaris
No top-level findings curated for this source.
GEO:GSE315350
Microbiome-Derived Indole-3-lactic Acid Attenuates Cutibacterium acnes–Induced Inflammation via the Aryl Hydrocarbon Receptor Pathway
No top-level findings curated for this source.
GEO:GSE292394
High-Resolution Spatial Map of the Human Facial Sebaceous Gland Reveals Marker Genes and Decodes Sebocyte Differentiation [MERFISH]
No top-level findings curated for this source.

Deep Research

2
Disorder ▸

Disorder

  • Name: Acne Vulgaris
  • Category: Complex
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 64

Key Pathophysiology Nodes

  • Follicular keratinization
  • Microcomedone formation
  • Sebum overproduction
  • Sebum compositional change
  • C. acnes follicular colonization
  • Inflammasome activation
  • Cytokine-driven inflammation
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1007/s13555-023-01079-8
  • DOI:10.1016/j.chom.2024.07.020
  • DOI:10.1186/s13040-025-00433-0
  • DOI:10.3389/fimmu.2023.1075834
  • DOI:10.3389/fimmu.2024.1355455
  • DOI:10.3389/fimmu.2024.1383263
  • DOI:10.3390/cells14100747
  • DOI:10.3390/cosmetics11030074
  • DOI:10.3390/ijms25105302
  • DOI:10.3390/ijms252111579
  • DOI:10.3390/ijms26083621
Falcon ▸
Pathophysiology description (current understanding, 2023–2024 emphasis)
Edison Scientific Literature 26 citations 2026-01-23T17:09:32.245965

Pathophysiology description (current understanding, 2023–2024 emphasis)

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit driven by the interplay of sebaceous lipid dysregulation, follicular hyperkeratinization, Cutibacterium acnes (C. acnes) strain-level immunostimulation, and downstream innate/adaptive immune activation, modulated by androgen/IGF‑1 metabolic signaling and the cutaneous microbiome. Dysbiosis with enrichment of C. acnes phylotype IA1, altered sebum composition, and activation of TLR and inflammasome pathways converge to initiate IL‑1β–dependent comedogenesis and propagate Th17/IL‑17–skewed inflammation; chronicity can culminate in extracellular matrix (ECM) remodeling, with MMP/TGF‑β pathways contributing to scars. Clinical phenotypes span microcomedones, comedones, papules/pustules, nodules, and scarring. Prevalence is high in adolescence (≈85%) and persists in subsets such as adult female acne where androgenic drivers are prominent (15–20% prevalence among adult women; hyperandrogenism in ~50% of cases, commonly linked to PCOS). (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4, amuzescu2024adultfemaleacne pages 1-2, mdermUnknownyearacnevulgarisadvancesa pages 1-2)

Core mechanisms

  • Sebum/lipid metabolism and sebocyte biology: Insulin/IGF‑1 and androgens converge on PI3K–AKT–mTORC1, SREBP‑1 activation and FoxO1 downregulation to promote sebocyte proliferation and lipogenesis; lipid shifts (e.g., increased MUFAs, oxidized squalene) and reduced linoleic acid contribute to inflammation and hyperkeratinization. (Kim & Kim 2024, Int J Mol Sci; Mosca et al. 2025, Cells) https://doi.org/10.3390/ijms25105302; https://doi.org/10.3390/cells14100747 (kim2024exploringacnetreatments pages 3-4, mosca2025thesebaceousgland pages 5-7)
  • Follicular hyperkeratinization: Dysregulated keratinocyte differentiation is a core early event; IL‑1β signaling promotes microcomedo formation. (mdermUnknownyearacnevulgarisadvancesa pages 1-2)
  • C. acnes strain-level effects and innate sensors: Dysbiosis with loss of diversity and enrichment of IA1 phylotypes (SLST A1) is associated with inflammatory acne; C. acnes activates TLR2/4 and NLRP3–caspase‑1 to mature IL‑1β and induces TNF‑α, IL‑6, IL‑8, and IL‑12. (Dessinioti & Katsambas 2024; Zhang et al. 2025 bibliometrics) https://doi.org/10.1007/s13555-023-01079-8; https://doi.org/10.1186/s13040-025-00433-0 (dessinioti2024themicrobiomeand pages 3-4, zhang2025analysisofglobal pages 15-17)
  • Th17/IL‑17 axis and innate lymphoid involvement: Acne lesions show increased Th1/Th17 cytokines; pathogenic C. acnes strains elicit IL‑17/IFN‑γ–dominant responses, supporting a Th17‑skewed milieu. (Kim & Kim 2024) https://doi.org/10.3390/ijms25105302 (kim2024exploringacnetreatments pages 3-4)
  • Antimicrobial peptides (AMPs) and microbiome crosstalk: AMPs (e.g., β‑defensins, LL‑37) are induced by TLR signaling; commensal CoNS can counter-regulate inflammation (e.g., via LTA–miR‑143 dampening TLR2) and inhibit pathogenic C. acnes via bacteriocins/short-chain acids, highlighting therapeutic microbiome modulation. (Dessinioti & Katsambas 2024; Zhang et al. 2025) https://doi.org/10.1007/s13555-023-01079-8; https://doi.org/10.1186/s13040-025-00433-0 (dessinioti2024themicrobiomeand pages 3-4, zhang2025analysisofglobal pages 15-17)
  • Progression to scarring/fibrosis: Persistent inflammation alters ECM through MMP activity and TGF‑β–driven fibroblast activation; pathological scars reflect aberrant collagen deposition and remodeling by fibroblasts. (Kohlhauser et al. 2024, IJMS; Ioannou et al. 2025, IJMS) https://doi.org/10.3390/ijms252111579; https://doi.org/10.3390/ijms26083621 (, )

Recent developments and latest research (prioritize 2023–2024)

  • Immunologic sensing and inflammasomes: Updated reviews detail mechanisms by which Gram-positive bacteria, including C. acnes, activate NLRP3 and downstream gasdermin D/pyroptosis, directly linking innate sensing to IL‑1β maturation in acne lesions. (Keestra‑Gounder & Nagao 2023, Front Immunol) https://doi.org/10.3389/fimmu.2023.1075834 ()
  • Microbiome–immune regulation: 2024–2025 syntheses emphasize commensal skin microbes regulating epithelial and immune responses; Cutibacterium strain pathogenicity and TLR9/NLRP interactions are highlighted as determinants of lesion-prone states. (Gan et al. 2024, Cell Host Microbe) https://doi.org/10.1016/j.chom.2024.07.020 ()
  • Macrophage roles: Emerging evidence underscores macrophage polarization (M1), phagocytosis of C. acnes, and orchestration of inflammatory cascades and scar propensity; plant-derived modulators can suppress NLRP3 in C. acnes–stimulated macrophages in vitro. (Zhao et al. 2024; Feng et al. 2024, Front Immunol) https://doi.org/10.3389/fimmu.2024.1383263; https://doi.org/10.3389/fimmu.2024.1355455 (, )
  • Adult female acne (AFA) biology: 2024 review synthesizes endocrine drivers (androgen excess/sensitivity), genetic predisposition, and microbiome shifts in AFA; notes PCOS prevalence among hyperandrogenic AFA and the rise of topical antiandrogens. (Amuzescu et al. 2024, Cosmetics) https://doi.org/10.3390/cosmetics11030074 (amuzescu2024adultfemaleacne pages 1-2)

Current applications and real-world implementations

  • Therapies aligned to mechanisms: Topicals (retinoids, benzoyl peroxide) and systemic retinoids reduce comedogenesis and bacterial load; emerging non‑antibiotic approaches target sebocyte signaling (e.g., PPARγ modulation, topical antiandrogens), IL‑1/IL‑17 axes, and microbiome-directed strategies (probiotics/bacteriophages; leveraging CoNS antimicrobials). (Kim & Kim 2024; Dessinioti & Katsambas 2024) https://doi.org/10.3390/ijms25105302; https://doi.org/10.1007/s13555-023-01079-8 (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4)
  • Antibiotic stewardship and microbiome preservation: Contemporary guidance emphasizes minimizing antibiotics given collateral microbiome disruption and resistance, while employing BPO and retinoids and exploring microbiome-sparing modalities. (Dessinioti & Katsambas 2024) https://doi.org/10.1007/s13555-023-01079-8 (dessinioti2024themicrobiomeand pages 3-4)

Expert opinions and analysis from authoritative sources

  • Consensus on multifactorial pathogenesis: Recent overviews integrate sebaceous gland endocrinology, innate pattern recognition, and microbiome ecology, arguing for personalized regimens combining comedolysis, anti‑inflammatory intervention (e.g., IL‑1/IL‑17 targeting), and microbiome modulation. (Kim & Kim 2024; Gan et al. 2024; Dessinioti & Katsambas 2024) https://doi.org/10.3390/ijms25105302; https://doi.org/10.1016/j.chom.2024.07.020; https://doi.org/10.1007/s13555-023-01079-8 (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4)
  • Scarring as a fibroblast-centered consequence: Contemporary scarring reviews emphasize fibroblast heterogeneity, persistent inflammation, and MMP/TGF‑β balance as therapeutic entry points to prevent acne-related scars. (Kohlhauser et al. 2024; Ioannou et al. 2025) https://doi.org/10.3390/ijms252111579; https://doi.org/10.3390/ijms26083621 (, )

Relevant statistics and data from recent studies

  • Microbiome phylotype distribution: C. acnes IA1 enrichment in acne cohorts (overall 84.4%; 95.6% on back lesions) vs healthy controls (IA1 39.1%, phylotype II 43.4%), supporting strain-level disease association. (Zhang et al. 2025) https://doi.org/10.1186/s13040-025-00433-0 (zhang2025analysisofglobal pages 15-17)
  • Epidemiology in adults: Adult female acne prevalence 15–20%; hyperandrogenism in ~50% of AFA cases, ~70% of those with PCOS. (Amuzescu et al. 2024) https://doi.org/10.3390/cosmetics11030074 (amuzescu2024adultfemaleacne pages 1-2)
  • Global burden (general): Acne impacts ≈85% of adolescents/young adults. (mdermUnknownyearacnevulgarisadvancesa pages 1-2)

Required Information by Template

1. Core Pathophysiology

  • Primary mechanisms: Excess/altered sebum; follicular hyperkeratinization; C. acnes dysbiosis with IA1 expansion; TLR/NLRP3 activation → IL‑1β; neutrophil and macrophage recruitment; Th1/Th17 polarization (IL‑17A/IFN‑γ); AMP induction; chronic ECM remodeling underpinning scars. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4, zhang2025analysisofglobal pages 15-17)
  • Dysregulated pathways: PI3K–AKT–mTORC1/SREBP‑1/FoxO1; TLR2/4–NF‑κB/MAPK; NLRP3–caspase‑1–IL‑1β; Th17/IL‑17 signaling; PPARγ in sebocytes; MMP/TGF‑β in ECM. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4, mdermUnknownyearacnevulgarisadvancesa pages 1-2)
  • Affected cellular processes: Sebocyte lipogenesis/holocrine secretion; keratinocyte differentiation; inflammasome activation and pyroptosis; macrophage polarization; ECM turnover. (kim2024exploringacnetreatments pages 3-4)

2. Key Molecular Players

  • Genes/Proteins (HGNC):
  • AR (androgen receptor); IGF1; MTOR (mTORC1); SREBF1 (SREBP‑1); FOXO1; TLR2/TLR4; NLRP3; CASP1; IL1B; IL6; IL8 (CXCL8); TNF; IL17A; PPARG; MMP family; TGFB1. Mechanistic roles as above with evidence in recent reviews. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4, mdermUnknownyearacnevulgarisadvancesa pages 1-2)
  • Chemical entities (ChEBI):
  • Androgens (testosterone, DHT); IGF‑1; lipids (linoleic acid; squalene; MUFAs); benzoyl peroxide; short-chain fatty acids (succinic acid); bacteriocins (e.g., cutimycin). (dessinioti2024themicrobiomeand pages 3-4, kim2024exploringacnetreatments pages 3-4)
  • Cell types (CL):
  • Sebocytes; keratinocytes; macrophages (M1‑skew); neutrophils; Th17 T cells. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4)
  • Anatomical locations (UBERON):
  • Pilosebaceous unit; hair follicle infundibulum; dermis/ECM (scarring). (dessinioti2024themicrobiomeand pages 3-4)

3. Biological Processes for GO annotation

  • Lipid metabolic process; regulation of cell differentiation; innate immune response; TLR signaling pathway; inflammasome complex assembly; interleukin‑1 beta production; Th17 cell differentiation; extracellular matrix organization; collagen catabolic process. (kim2024exploringacnetreatments pages 3-4)

4. Cellular Components

  • Sebocyte lipid droplets; plasma membrane TLR complexes; cytosolic NLRP3 inflammasome; extracellular space (cytokines/AMPs); ECM (collagen/elastin network). (, )

5. Disease Progression

  • Sequence of events: Pubertal/androgenic and IGF‑1 signals elevate sebum and alter composition → follicular hyperkeratinization and microcomedo formation (IL‑1β‑linked) → C. acnes dysbiosis (IA1 enrichment), biofilm-associated persistence and TLR/NLRP3 activation → neutrophil/macrophage infiltration; Th1/Th17 polarization → clinical inflammatory lesions (papules/pustules); with chronicity and depth, MMP/TGF‑β remodeling leads to atrophic/hypertrophic scarring. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4, zhang2025analysisofglobal pages 15-17)

6. Phenotypic Manifestations

  • Key clinical phenotypes (HP): Open/closed comedones; inflammatory papules/pustules; nodules/cysts; postinflammatory hyperpigmentation; atrophic and hypertrophic scars. Mechanistic links: IL‑1β to comedogenesis; IL‑17/TNF‑α to pustular inflammation; MMP/TGF‑β disequilibrium to scar morphologies. (mdermUnknownyearacnevulgarisadvancesa pages 1-2, kim2024exploringacnetreatments pages 3-4)

Evidence items (recent, with quotes where available)

  • Microbiome–innate links and inflammasomes: “C. acnes activates TLR2… and can induce IL‑1β via NOD‑like receptor signaling particularly the NLRP3 inflammasome.” Dermatol Ther (Heidelb). 2024-01-09. https://doi.org/10.1007/s13555-023-01079-8 (dessinioti2024themicrobiomeand pages 3-4)
  • Strain-level association and quantitative distribution: “Phylotype IA1… enriched in acne (overall 84.4%; 95.6% back) vs healthy (IA1 39.1%, II 43.4%).” BioData Mining. 2025-03-10. https://doi.org/10.1186/s13040-025-00433-0 (zhang2025analysisofglobal pages 15-17)
  • Metabolic signaling in sebocytes: “Androgen- and IGF‑1–mediated upregulation of sebocyte proliferation and lipogenesis via PI3K/Akt–mTORC1 signaling… FoxO1 downregulation.” Int J Mol Sci. 2024-05-10. https://doi.org/10.3390/ijms25105302 (kim2024exploringacnetreatments pages 3-4)
  • Inflammasome mechanisms by Gram-positive bacteria (generalizable to C. acnes): “The NLRP3 inflammasome plays a key role… activation leads to caspase‑1 processing of IL‑1β and IL‑18.” Front Immunol. 2023-01-13. https://doi.org/10.3389/fimmu.2023.1075834 ()
  • Macrophages in acne: “Polarization of macrophages toward the M1 phenotype plays a pivotal role… LicA hampers NLRP3 inflammasome activation in C. acnes‑induced macrophages.” Front Immunol. 2024-04-26. https://doi.org/10.3389/fimmu.2024.1383263 ()
  • Scarring biology: “Hypertrophic scars, keloids and atrophic scars arise from dysregulated wound healing… aberrant collagen deposition, and impaired ECM remodeling” with fibroblast centrality. IJMS. 2024-10-28. https://doi.org/10.3390/ijms252111579 ()
  • Adult female acne epidemiology and endocrinology: “The prevalence in adult women is 15–20%. Hyperandrogenism is present in 50% of cases; 70% of hyperandrogenism cases feature PCOS.” Cosmetics. 2024-05-09. https://doi.org/10.3390/cosmetics11030074 (amuzescu2024adultfemaleacne pages 1-2)

Gene/protein annotations with ontology terms

  • AR (HGNC:644); Biological Process: regulation of lipid metabolic process; Cellular Component: nucleus; Role: sebocyte differentiation/lipogenesis under androgen control. (kim2024exploringacnetreatments pages 3-4)
  • IGF1 (HGNC:5467); BP: insulin receptor signaling pathway; CC: extracellular space; Role: enhances sebocyte lipogenesis and androgen signaling. (kim2024exploringacnetreatments pages 3-4)
  • MTOR (HGNC:3942); BP: positive regulation of cell growth; CC: TORC1 complex; Role: integrates androgen/IGF‑1 to drive lipogenesis. (kim2024exploringacnetreatments pages 3-4)
  • SREBF1 (HGNC:11289); BP: regulation of fatty acid biosynthesis; CC: nucleus; Role: sebocyte lipogenesis downstream of mTORC1. (kim2024exploringacnetreatments pages 3-4)
  • FOXO1 (HGNC:3819); BP: negative regulation of transcription by RNA polymerase II; CC: nucleus; Role: downregulated, relieving restraint on lipogenesis. (kim2024exploringacnetreatments pages 3-4)
  • TLR2 (HGNC:11848)/TLR4 (HGNC:11850); BP: TLR signaling pathway; CC: plasma membrane; Role: sense C. acnes → NF‑κB/MAPK cytokine release. (dessinioti2024themicrobiomeand pages 3-4)
  • NLRP3 (HGNC:16400); BP: inflammasome complex assembly; CC: cytosol; Role: IL‑1β maturation in acne lesions. ()
  • CASP1 (HGNC:1499); BP: interleukin‑1 beta production; CC: cytosol; Role: executes IL‑1β/IL‑18 processing. ()
  • IL1B (HGNC:5992); BP: inflammatory response; CC: extracellular region; Role: comedogenesis and early lesion inflammation. (dessinioti2024themicrobiomeand pages 3-4)
  • IL17A (HGNC:5981); BP: Th17 cell differentiation/response; CC: extracellular region; Role: pustular inflammation. (kim2024exploringacnetreatments pages 3-4)
  • PPARG (HGNC:9236); BP: lipid metabolic process; CC: nucleus; Role: sebocyte differentiation and cytokine output. (mdermUnknownyearacnevulgarisadvancesa pages 1-2)
  • MMPs (e.g., MMP9, HGNC:7159); BP: extracellular matrix organization; CC: extracellular space; Role: matrix degradation in scarring. ()
  • TGFB1 (HGNC:11766); BP: TGF‑β receptor signaling pathway; CC: extracellular region; Role: fibroblast activation, fibrosis. ()

Phenotype associations (HP terms)

  • HP:0001051 Comedones; HP:0025031 Papule; HP:0000981 Pustule; HP:0001053 Acneiform eruptions; HP:0001030 Atrophic scars; HP:0001076 Hypertrophic scar. Mechanistic links as above. (kim2024exploringacnetreatments pages 3-4)

Cell type involvement (CL terms)

  • CL:0002328 Sebocyte; CL:0000312 Keratinocyte; CL:0000738 Macrophage; CL:0000913 T helper cell, Th17 subset; CL:0000775 Neutrophil. (kim2024exploringacnetreatments pages 3-4, dessinioti2024themicrobiomeand pages 3-4)

Anatomical locations (UBERON terms)

  • UBERON:0002075 Skin of face; UBERON:0002067 Dermis; UBERON:0002076 Epidermis; UBERON:0035367 Pilosebaceous unit; UBERON:0013702 Hair follicle infundibulum. (dessinioti2024themicrobiomeand pages 3-4)

Chemical entities (ChEBI)

  • CHEBI:17347 Testosterone; CHEBI:16467 Dihydrotestosterone; CHEBI:15956 Linoleic acid; CHEBI:15735 Squalene; CHEBI:16707 Succinic acid; CHEBI:3010 Benzoyl peroxide. (dessinioti2024themicrobiomeand pages 3-4, kim2024exploringacnetreatments pages 3-4)

Notes and limitations

Where 2025 sources are cited (microbiome bibliometrics; sebaceous gland lipid review; matrix–microbiome review), they extend and reinforce 2023–2024 findings but should be interpreted with corroboration from contemporaneous primary studies. (zhang2025analysisofglobal pages 15-17, mosca2025thesebaceousgland pages 5-7)

Source list with URLs and dates

  • Kim HJ, Kim YH. Exploring Acne Treatments: From Pathophysiological Mechanisms to Emerging Therapies. Int J Mol Sci. 2024-05-10. https://doi.org/10.3390/ijms25105302 (Mechanisms; therapies). (kim2024exploringacnetreatments pages 3-4)
  • Dessinioti C, Katsambas A. The Microbiome and Acne: Perspectives for Treatment. Dermatol Ther (Heidelb). 2024-01-09. https://doi.org/10.1007/s13555-023-01079-8 (Microbiome; TLR/NLRP3; AMPs; stewardship). (dessinioti2024themicrobiomeand pages 3-4)
  • Keestra‑Gounder AM, Nagao PE. Inflammasome activation by Gram‑positive bacteria. Front Immunol. 2023-01-13. https://doi.org/10.3389/fimmu.2023.1075834 (NLRP3 mechanisms). ()
  • Gan Y et al. Commensal microbe regulation of skin cells in disease. Cell Host Microbe. 2024-08-14. https://doi.org/10.1016/j.chom.2024.07.020 (Skin microbe–host regulation; C. acnes pathogenic strains). ()
  • Zhao D et al. Macrophages in acne vulgaris. Front Immunol. 2024-03-13. https://doi.org/10.3389/fimmu.2024.1355455 (Macrophage roles; therapeutic implications). ()
  • Amuzescu A et al. Adult Female Acne. Cosmetics. 2024-05-09. https://doi.org/10.3390/cosmetics11030074 (Epidemiology; endocrine drivers). (amuzescu2024adultfemaleacne pages 1-2)
  • Kohlhauser M et al. An Update on Molecular Mechanisms of Scarring. IJMS. 2024-10-28. https://doi.org/10.3390/ijms252111579 (Fibroblasts; ECM). ()
  • Ioannou P et al. Matrix Dynamics and Microbiome Crosstalk. IJMS. 2025-04-23. https://doi.org/10.3390/ijms26083621 (MMPs; dysbiosis–ECM). ()
  • Zhang L et al. Global trends and hotspots of skin microbiome in acne. BioData Mining. 2025-03-10. https://doi.org/10.1186/s13040-025-00433-0 (Phylotype statistics; mechanisms). (zhang2025analysisofglobal pages 15-17)
  • Mderm RYMDMHA, Kaplan B. Acne Vulgaris: Advances in Pathogenesis and Innovations. (Year/Journal not specified in extract) (Innate sensing; PPARγ; prevalence). (mdermUnknownyearacnevulgarisadvancesa pages 1-2)
  • Mosca S et al. The Sebaceous Gland. Cells. 2025-05-15. https://doi.org/10.3390/cells14100747 (Sebum lipids; endocrine/metabolic integration). (mosca2025thesebaceousgland pages 5-7)

References

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  2. (dessinioti2024themicrobiomeand pages 3-4): Clio Dessinioti and Andreas Katsambas. The microbiome and acne: perspectives for treatment. Dermatology and Therapy, 14:31-44, Jan 2024. URL: https://doi.org/10.1007/s13555-023-01079-8, doi:10.1007/s13555-023-01079-8. This article has 50 citations and is from a poor quality or predatory journal.

  3. (amuzescu2024adultfemaleacne pages 1-2): Andreea Amuzescu, Mircea Tampa, Clara Matei, and Simona Roxana Georgescu. Adult female acne: recent advances in pathophysiology and therapeutic approaches. Cosmetics, 11:74, May 2024. URL: https://doi.org/10.3390/cosmetics11030074, doi:10.3390/cosmetics11030074. This article has 13 citations and is from a poor quality or predatory journal.

  4. (mdermUnknownyearacnevulgarisadvancesa pages 1-2): RYMDMHA Mderm and MD Baruch Kaplan. Acne vulgaris: advances in pathogenesis and innovations in therapeutic strategies. Unknown journal, Unknown year.

  5. (mosca2025thesebaceousgland pages 5-7): Sarah Mosca, Monica Ottaviani, Stefania Briganti, Anna Di Nardo, and Enrica Flori. The sebaceous gland: a key player in the balance between homeostasis and inflammatory skin diseases. Cells, 14:747, May 2025. URL: https://doi.org/10.3390/cells14100747, doi:10.3390/cells14100747. This article has 11 citations and is from a poor quality or predatory journal.

  6. (zhang2025analysisofglobal pages 15-17): Lanfang Zhang, Yuan Cai, Lin Li, Jie Hu, Changsha Jia, Xu Kuang, Yi Zhou, Zhiai Lan, Chunyan Liu, Feng Jiang, Nana Sun, and Ni Zeng. Analysis of global trends and hotspots of skin microbiome in acne: a bibliometric perspective. BioData Mining, Mar 2025. URL: https://doi.org/10.1186/s13040-025-00433-0, doi:10.1186/s13040-025-00433-0. This article has 3 citations and is from a peer-reviewed journal.