Atopic Dermatitis

Complex MONDO:0004980 Pathograph 10 Dermatological Disease Chronic Inflammatory Disease Allergic Disease

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8
Pathophys.
13
Phenotypes
1
Gaps
10
Pathograph
13
Genes
6
Medical Actions
4
Subtypes
9
References
2
Deep Research
◆

Subtypes

4
Early-Onset Atopic Dermatitis
Onset in infancy or early childhood, often associated with the atopic march progressing to asthma and allergic rhinitis.
Adult-Onset Atopic Dermatitis
First presentation in adulthood, often with different clinical distribution and associations compared to childhood-onset disease.
Extrinsic Atopic Dermatitis
Associated with IgE-mediated sensitization to environmental allergens. Elevated serum IgE and positive skin prick tests.
Intrinsic Atopic Dermatitis
Without IgE-mediated sensitization. Normal serum IgE levels. Represents approximately 20% of cases.
C

Comorbidities

Atopic Dermatitis <-> Type 2 Diabetes Mellitus
Disease A A_BEFORE_B CANDIDATE
?

Discussions and Knowledge Gaps

1
TOPK (PBK) is upregulated in atopic dermatitis and its inhibition attenuates AD-like inflammation via STAT3 Ser727 phosphorylation in keratinocytes and mast cells, but is TOPK-STAT3 signaling a primary causal driver of AD pathogenesis or a downstream amplifier of the established type 2 / barrier circuit, what is its dominant in vivo cellular source, and does the axis translate from cell and mouse models to human disease?
KNOWLEDGE GAP OPEN gap_ad_topk_stat3_axis
Attached to
pathophysiology#Type 2 Immune Response pathophysiology#Epidermal Barrier Dysfunction pathophysiology#Secondary Inflammatory Amplification
Atopic dermatitis pathogenesis is well characterized at the level of epidermal barrier dysfunction and the IL-4/IL-13/IL-31 type 2 immune program signaling through JAK1/STAT6, which underpins approved biologic and JAK- inhibitor therapies. Recent work identifies T-LAK-cell-originated protein kinase (TOPK) as upregulated in AD lesions, where it directly interacts with and phosphorylates STAT3 at Ser727 in HaCaT keratinocytes and mast cells, and where genetic or pharmacologic TOPK inhibition reduces IgE, IL-6, IL-8, and IL-33 and attenuates AD-like features. What remains unresolved is the causal placement of this TOPK-STAT3 axis: whether it initiates inflammation upstream of, runs in parallel to, or is induced by the canonical type 2 and barrier pathways, and whether STAT3 Ser727 signaling acts mainly in keratinocytes, mast cells, or other resident/infiltrating cells in intact skin. The current evidence rests largely on cell lines, bioinformatic (GEO) profiling, and a disease model, so the human translational relevance and therapeutic window of TOPK inhibition relative to existing STAT6/JAK-directed therapies is unknown.
Proposed experiments
Cell-type-resolved epistasis of the TOPK-STAT3 axis versus the type 2 barrier circuit
cell-type-conditional perturbation and epistasis study
exp_ad_topk_stat3_epistasis
Use cell-type-conditional TOPK loss- and gain-of-function in barrier and immune compartments of AD models, combined with epistasis against IL-4/ IL-13 (type 2) and barrier perturbations and STAT3 Ser727 phospho-readouts, to place TOPK-STAT3 in the causal hierarchy and identify the dominant in vivo cellular source. Cross-validate against human AD skin to test translational relevance.
Readouts
STAT3 Ser727 phosphorylation by compartment
pathophysiology#Secondary Inflammatory Amplification
Quantify STAT3 Ser727 phosphorylation in keratinocytes versus mast cells and other skin-resident cells under TOPK perturbation to localize the active signaling compartment.
phospho-specific immunostaining phosphoproteomic profiling
Direction: POSITIVE
Type 2 cytokine and barrier dependence
pathophysiology#Type 2 Immune Response
Test whether TOPK-driven inflammation persists when IL-4/IL-13 signaling is blocked, distinguishing an upstream/parallel driver from a type 2- dependent amplifier.
cytokine quantification
Direction: NEGATIVE
Barrier integrity response to TOPK modulation
pathophysiology#Epidermal Barrier Dysfunction
Measure transepidermal water loss and barrier protein expression after TOPK inhibition to determine whether the axis modifies barrier function directly or only via inflammation.
transepidermal water loss measurement
Direction: NEGATIVE
Decision criterion
TOPK-STAT3 is supported as a primary driver if compartment-conditional TOPK loss reduces AD-like inflammation independently of (and upstream of) intact IL-4/IL-13 signaling, with the dominant active STAT3 Ser727 compartment reproducibly identified and the axis detectable in human AD skin; it is a downstream amplifier if its effects require an intact type 2 circuit.
Would support
pathophysiology#Type 2 Immune Response pathophysiology#Secondary Inflammatory Amplification pathophysiology#Epidermal Barrier Dysfunction
Show evidence (2 references)
PMID:42237026 SUPPORT In Vitro
"T-Lymphokine-Activated Killer Cell-Originated Protein Kinase (TOPK) is known to promote inflammation, its specific role in AD remains unclear."
Establishes that TOPK is implicated in inflammation but its specific mechanistic role in atopic dermatitis is unresolved, motivating the gap.
PMID:42237026 SUPPORT In Vitro
"TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
Defines the proposed TOPK-STAT3 Ser727 mechanism in keratinocytes and mast cells, the candidate axis whose causal placement and cellular source the gap seeks to resolve.
⚙

Pathophysiology

8
Epidermal Barrier Dysfunction
Loss-of-function mutations in filaggrin (FLG) and other barrier proteins lead to impaired skin barrier integrity, increased transepidermal water loss, and enhanced allergen penetration. This is the primary initiating event in many patients.
Keratinocyte CL:0000312
FLG hgnc:3748
Keratinization GO:0031424
Show evidence (2 references)
PMID:16550169 SUPPORT Human Clinical
"Filaggrin is a key protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Here we show that two independent loss-of-function genetic variants (R510X [sic, correct designation is R501X] and 2282del4) in the gene encoding filaggrin (FLG) are very..."
Landmark study establishing FLG loss-of-function as the strongest genetic risk factor for atopic dermatitis, with ~9% carrier frequency in Europeans.
PMID:21388665 PARTIAL Human Clinical
"They are similar in that they are complex inherited diseases involving genes that encode immune components and structural proteins that regulate differentiation of epidermal cells. Each disease is characterized by proliferation of epidermal keratinocytes and abnormal cornification or terminal..."
Describes the epidermal barrier dysfunction in atopic dermatitis including abnormal cornification and keratinocyte differentiation.
Type 2 Immune Response
Th2-skewed immune response drives the hallmark inflammation. IL-4, IL-13, and IL-31 promote IgE production, eosinophil recruitment, and pruritus. IL-4/IL-13 signaling through JAK1/STAT6 further impairs barrier function by downregulating filaggrin and other barrier proteins.
T-helper 2 cell CL:0000546 Group 2 innate lymphoid cell CL:0001069 Eosinophil CL:0000771 Mast cell CL:0000097
IL4 hgnc:6014 IL13 hgnc:5973 IL31 hgnc:19372 STAT6 hgnc:11368
Type 2 immune response GO:0042092 T-helper 2 cell differentiation GO:0045064 Interleukin-4-mediated signaling pathway GO:0035771 IgE isotype switching GO:0035708
Downstream
Epidermal Barrier Dysfunction IL-4 and IL-13 downregulate filaggrin expression, creating a vicious cycle of barrier disruption and immune activation.
Pruritogen-Induced Neuronal Activation IL-31 signaling contributes to neuronal itch signaling in lesional skin.
Show evidence (2 references)
PMID:30819278 SUPPORT Human Clinical
"Type 2 cytokines as well as interleukin 17 and interleukin 22 contribute to skin barrier dysfunction and the development of AD."
Confirms the role of type 2 cytokines in AD pathophysiology and their contribution to barrier dysfunction, supporting the Th2/type 2 immune mechanism.
PMID:21388665 PARTIAL Human Clinical
"skin lesions contain immune infiltrates of T cells, dendritic cells, and other types of leukocytes. We review similarities between the diseases and differences in epidermal barrier defects and immune cells."
Describes the immune cell infiltrates in AD lesions including T cells and dendritic cells, consistent with type 2 immune response.
TOPK-STAT3 Signaling Axis
T-Lymphokine-Activated Killer Cell-Originated Protein Kinase (TOPK) is upregulated in AD and directly phosphorylates STAT3 at Ser727 in keratinocytes and mast cells, driving the production of inflammatory cytokines (IL-6, IL-8, IL-33) and IgE dysregulation. This axis acts as an amplifier of the type 2 immune response.
Keratinocyte CL:0000312 Mast cell CL:0000097
PBK hgnc:18282 STAT3 hgnc:11364
Protein phosphorylation GO:0006468 Interleukin-6 production GO:0032635 Interleukin-8 production GO:0032637
Downstream
Type 2 Immune Response TOPK-mediated STAT3 Ser727 phosphorylation amplifies IL-6 and IL-8 production, enhancing Th2 polarization and IgE responses.
Secondary Inflammatory Amplification TOPK-STAT3 signaling perpetuates keratinocyte and mast cell inflammatory output, sustaining chronic lesion inflammation.
Show evidence (2 references)
PMID:42237026 SUPPORT In Vitro
"TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
Establishes TOPK-STAT3 Ser727 phosphorylation as the direct mechanistic driver of inflammatory responses in AD-relevant cell types.
PMID:42237026 SUPPORT Model Organism
"Genetic or pharmacological inhibition of TOPK markedly attenuated AD-like pathological features and reduces the levels of IgE, IL-6, IL-8 and IL-33"
Demonstrates that TOPK inhibition reduces multiple AD-associated inflammatory mediators and IgE dysregulation.
Th17/Th22 Inflammation
In addition to the dominant Th2 response, Th17 and Th22 cells contribute to inflammation, particularly in acute lesions and Asian patients. IL-17 and IL-22 further disrupt epidermal differentiation.
T-helper 17 cell CL:0000899
T-helper 17 type immune response GO:0072538
TOPK-STAT3 Signaling Axis
TOPK (T-Lymphokine-Activated Killer cell-Originated Protein Kinase) is upregulated in atopic dermatitis lesions and directly phosphorylates STAT3 at Ser727 in keratinocytes and mast cells, amplifying inflammatory responses including IL-6, IL-8, and IL-33 production. TOPK-driven STAT3 activation contributes to the maintenance of AD-associated inflammation.
Keratinocyte CL:0000312 Mast cell CL:0000097
PBK hgnc:18282 STAT3 hgnc:11364
Cytokine production GO:0001816 Signal transduction GO:0007165
Downstream
Secondary Inflammatory Amplification TOPK-mediated STAT3 Ser727 phosphorylation drives IL-6, IL-8, and IL-33 production, amplifying chronic skin inflammation.
Show evidence (3 references)
PMID:42237026 SUPPORT Computational
"Bioinformatics analysis revealed that TOPK was significantly upregulated in AD patients."
GEO database bioinformatics analysis establishes TOPK upregulation in AD patient transcriptomes.
PMID:42237026 SUPPORT Model Organism
"Genetic or pharmacological inhibition of TOPK markedly attenuated AD-like pathological features and reduces the levels of IgE, IL-6, IL-8 and IL-33, suggesting that TOPK contributes to AD pathogenesis."
Animal model demonstrates TOPK's functional contribution to AD-like inflammatory pathology and cytokine production.
PMID:42237026 SUPPORT In Vitro
"TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
Defines the TOPK-STAT3 Ser727 phosphorylation mechanism in keratinocytes and mast cells, the key cellular sources of the AD inflammatory axis.
Pruritogen-Induced Neuronal Activation
IL-31 and other pruritogens activate cutaneous sensory neurons, generating persistent itch in atopic dermatitis.
Sensory neuron CL:0000101
IL31 hgnc:19372
Downstream
Scratching-Induced Barrier Injury Persistent itch drives repetitive scratching behavior.
Show evidence (1 reference)
PMID:30819278 PARTIAL Human Clinical
"New insights into the pathophysiology of AD have focused on epidermal lipid profiles, neuroimmune interactions, and microbial dysbiosis."
Supports neuroimmune signaling as a component of AD pathophysiology.
Scratching-Induced Barrier Injury
Repetitive scratching causes mechanical skin injury and worsens epidermal barrier dysfunction.
Keratinocyte CL:0000312
Downstream
Secondary Inflammatory Amplification Mechanical barrier injury increases local inflammatory activation.
Secondary Inflammatory Amplification
Barrier injury from scratching perpetuates inflammatory signaling and contributes to chronic lesion persistence.
Keratinocyte CL:0000312
Inflammatory response GO:0006954
⬡

Pathograph

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

Phenotypes

13
Blood 1
Elevated Serum IgE FREQUENT Increased circulating IgE concentration HP:0003212
Present in extrinsic subtype (~80% of patients).
Show evidence (1 reference)
PMID:20207111 SUPPORT
"Extrinsic or allergic AD shows high total serum IgE levels and the presence of specific IgE for environmental and food allergens... While extrinsic AD is the classical type with high prevalence, the incidence of intrinsic AD is approximately 20%"
Approximately 80% of atopic dermatitis patients have the extrinsic subtype characterized by elevated serum IgE levels.
Cardiovascular 1
Erythema VERY_FREQUENT Erythema HP:0010783
Erythematous patches and plaques are a core clinical feature, often the earliest visible sign of active disease.
Show evidence (1 reference)
PMID:39659858 SUPPORT Human Clinical
"a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus"
Erythematous rash is listed as one of the three cardinal features of atopic dermatitis.
Immune 2
Eczematoid Dermatitis VERY_FREQUENT Eczematoid dermatitis HP:0000964
Erythematous, pruritic patches and plaques with scaling, often in flexural areas.
Show evidence (1 reference)
PMID:28846349 SUPPORT
"This chronic disorder associated with pruritus usually starts in infancy and presents with dry skin, eczematous lesions and lichenification."
Eczematous lesions are a defining feature of atopic dermatitis.
Food Allergy FREQUENT Food allergy HP:0500093
A common comorbidity, particularly in early-onset and severe AD. Part of the atopic march in a subset of patients. Epicutaneous sensitization through the disrupted skin barrier may drive food allergy development.
Show evidence (2 references)
PMID:32738956 SUPPORT Human Clinical
"Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
Lancet 2020 review identifies food allergy as a major AD comorbidity.
PMID:28846349 SUPPORT Human Clinical
"AD is associated with other IgE associated disorders like allergic rhinitis, asthma, and food allergies."
Confirms the well-established association between AD and food allergies as IgE-mediated comorbidities.
Integument 3
Pruritus VERY_FREQUENT Pruritus HP:0000989
Intense itching is the hallmark symptom, often worse at night.
Show evidence (1 reference)
PMID:39659858 SUPPORT
"Atopic dermatitis, more commonly known as atopic eczema, is a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus."
Intense pruritus is a defining clinical characteristic of atopic dermatitis.
Xerosis VERY_FREQUENT Dry skin HP:0000958
Generalized dry skin reflecting barrier dysfunction.
Show evidence (1 reference)
PMID:39659858 SUPPORT
"Atopic dermatitis, more commonly known as atopic eczema, is a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus."
Dry skin (xerosis) is a defining clinical characteristic of atopic dermatitis reflecting barrier dysfunction.
Keratosis Pilaris OCCASIONAL Keratosis pilaris HP:0032152
Follicular keratotic papules on extensor surfaces, associated with filaggrin-related barrier dysfunction and ichthyosis vulgaris.
Show evidence (1 reference)
PMID:31536314 SUPPORT Human Clinical
"Keratosis pilaris is associated with many other conditions, including atopic dermatitis, ichthyosis vulgaris, obesity, diabetes mellitus, and malnutrition."
StatPearls reference directly identifies atopic dermatitis as one of the conditions associated with keratosis pilaris.
Nervous System 1
Sleep Disturbance FREQUENT Sleep disturbance HP:0002360
Pruritus-driven sleep disruption is a major contributor to reduced quality of life, with severity correlating with disease activity.
Show evidence (1 reference)
PMID:38864389 SUPPORT Human Clinical
"AD patients reported lower sleep quality (p = 0.002), more severe insomnia (p = 0.006) and depression (p = 0.013), and higher stress levels than healthy adults (p = 0.049)."
Case-control study demonstrating significantly impaired sleep quality and increased insomnia in AD patients compared to matched controls.
Other 5
Flexural Lichenification FREQUENT Flexural lichenification HP:0007453
Lichenification preferentially affects flexural areas (antecubital and popliteal fossae, neck) and is a hallmark distribution pattern. Thickened, leathery skin develops from chronic scratching.
Show evidence (2 references)
PMID:28846349 SUPPORT Human Clinical
"This chronic disorder associated with pruritus usually starts in infancy and presents with dry skin, eczematous lesions and lichenification."
Lichenification is a defining chronic feature of atopic dermatitis.
PMID:35297082 SUPPORT Human Clinical
"Core AD features are similar between children and adults overall, including lesions affecting flexural areas, presence of atopy, and xerosis."
Flexural distribution is identified as a core feature of atopic dermatitis across age groups.
Recurrent Skin Infections FREQUENT Recurrent skin infections HP:0001581
Compromised barrier function and immune dysregulation predispose to bacterial (S. aureus), viral (HSV, molluscum), and fungal skin infections.
Show evidence (2 references)
PMID:31755570 SUPPORT Human Clinical
"Due to compromised barrier function and immune dysregulation, children with atopic dermatitis (AD) are at increased risk of cutaneous infections"
Establishes that barrier dysfunction and immune dysregulation in AD lead to increased risk of cutaneous infections.
PMID:35490395 SUPPORT Human Clinical
"Atopic dermatitis (AD) is associated with an increased risk for viral infections including those caused by herpes simplex virus and varicella zoster virus."
Confirms increased susceptibility to viral skin infections in AD patients.
Dennie-Morgan Infraorbital Folds FREQUENT Periorbital wrinkles HP:0000607
Dennie-Morgan folds are prominent infraorbital creases characteristic of atopic dermatitis, more common in children. Present in both extrinsic and intrinsic subtypes.
Show evidence (2 references)
PMID:35297082 SUPPORT Human Clinical
"children with AD have more exudative lesions, perifollicular accentuation, pityriasis alba, Dennie-Morgan folds, and seborrheic dermatitis-like presentation."
Dennie-Morgan folds (infraorbital creases associated with periorbital hyperpigmentation) are identified as a characteristic pediatric AD feature.
PMID:20207111 SUPPORT Human Clinical
"The clinical features of intrinsic AD include relative late onset, milder severity, and Dennie-Morgan folds, but no ichthyosis vulgris or palmar hyperlinearity."
Dennie-Morgan folds are present across both extrinsic and intrinsic AD subtypes.
Allergic Rhinitis FREQUENT Allergic rhinitis HP:0003193
A common atopic comorbidity, often developing after the onset of AD as part of the atopic march in some patients.
Show evidence (2 references)
PMID:32738956 SUPPORT Human Clinical
"Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
Lancet 2020 review identifies allergic rhinitis as a major AD comorbidity.
PMID:35297082 SUPPORT Human Clinical
"Atopic diseases commonly co-occur with AD, although most do not temporally have the "atopic march.""
Confirms atopic comorbidities co-occur with AD, while noting that the temporal sequence of the atopic march is not universal.
Asthma FREQUENT Asthma HP:0002099
A major atopic comorbidity. Part of the classic atopic triad alongside allergic rhinitis. Epicutaneous sensitization through the disrupted skin barrier may contribute to airway sensitization.
Show evidence (2 references)
PMID:32738956 SUPPORT Human Clinical
"Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
Lancet 2020 review identifies asthma as a major AD comorbidity.
PMID:30819278 SUPPORT Human Clinical
"An impaired skin barrier may be the initial step in the development of the atopic march as well as AD, which leads to further skin inflammation and allergic sensitization."
Links impaired skin barrier in AD to the development of the atopic march, including progression to asthma.
🧬

Genetic Associations

13
FLG (Associated)
Show evidence (1 reference)
PMID:16550169 SUPPORT Human Clinical
"two independent loss-of-function genetic variants (R510X [sic, correct designation is R501X] and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis. These variants are carried by approximately 9% of people of European origin."
Landmark Palmer et al. 2006 study establishing FLG loss-of-function as the major genetic predisposing factor for atopic dermatitis.
IL4R (Associated)
IL13 (Associated)
STAT6 (Associated)
EMSY (Associated)
BACH2 (GWAS)
TNFAIP3 (GWAS)
EGR2 (GWAS)
ETS1 (GWAS)
IRF4 (GWAS)
SATB1 (GWAS)
SMAD3 (GWAS)
REL (GWAS)
💊

Medical Actions

6
Emollients and Moisturizers
First-line treatment to restore skin barrier function and reduce transepidermal water loss.
Topical Corticosteroids
First-line anti-inflammatory treatment for flares, applied to affected areas.
Dupilumab
Action: biologic therapy Ontology label: Immunotherapy NCIT:C15262
Agent: dupilumab NCIT:C162455
Monoclonal antibody targeting IL-4 receptor alpha, blocking both IL-4 and IL-13 signaling. FDA-approved for moderate-to-severe atopic dermatitis.
JAK Inhibitors
Action: JAK inhibitor therapy Ontology label: immune suppressant agent therapy MAXO:0000297
Oral (baricitinib, upadacitinib, abrocitinib) and topical (ruxolitinib) JAK inhibitors targeting the JAK-STAT pathway downstream of type 2 cytokines.
Phototherapy
Narrowband UVB phototherapy for moderate-to-severe disease.
TOPK Inhibitors
Small-molecule inhibitors of TOPK (PBK) that target the TOPK-STAT3 signaling axis in keratinocytes and mast cells. Pharmacological or genetic TOPK inhibition attenuates AD-like pathological features and reduces inflammatory cytokine levels (IL-6, IL-8, IL-33, IgE).
Mechanism Target:
TOPK-STAT3 Signaling Axis — TOPK inhibitors block TOPK-mediated STAT3 Ser727 phosphorylation and downstream inflammatory cytokine production.
🌍

Environmental Factors

3
Allergen Exposure
House dust mites, pet dander, and pollens can trigger or exacerbate disease.
Skin Irritants
Soaps, detergents, and harsh fabrics disrupt the already compromised barrier.
Microbial Dysbiosis
Staphylococcus aureus colonization is found in >90% of lesional skin and amplifies inflammation through superantigens and biofilm formation.
{ }

Source YAML

click to show 
name: Atopic Dermatitis
creation_date: '2025-12-18T17:01:35Z'
updated_date: '2026-04-30T20:45:00Z'
category: Complex
parents:
- Dermatological Disease
- Chronic Inflammatory Disease
- Allergic Disease
has_subtypes:
- name: Early-Onset Atopic Dermatitis
  description: Onset in infancy or early childhood, often associated with the atopic march progressing to asthma and allergic rhinitis.
- name: Adult-Onset Atopic Dermatitis
  description: First presentation in adulthood, often with different clinical distribution and associations compared to childhood-onset disease.
- name: Extrinsic Atopic Dermatitis
  description: Associated with IgE-mediated sensitization to environmental allergens. Elevated serum IgE and positive skin prick tests.
- name: Intrinsic Atopic Dermatitis
  description: Without IgE-mediated sensitization. Normal serum IgE levels.
    Represents approximately 20% of cases.
prevalence:
- population: Global
  notes: >-
    Atopic dermatitis is the most common chronic inflammatory skin disease
    and the leading cause of global burden from skin disease. Prevalence
    estimates range from 15-20% in children to 2-10% in adults, varying
    by geography, with higher rates in industrialized nations. Prevalence
    has been increasing over recent decades.
  evidence:
  - reference: PMID:32738956
    reference_title: Atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic dermatitis is a common inflammatory skin disorder characterised by recurrent eczematous lesions and intense itch. The disorder affects people of all ages and ethnicities, has a substantial psychosocial impact on patients and relatives, and is the leading cause of the global burden from skin disease."
    explanation: Langan et al. Lancet 2020 comprehensive review confirms AD as the leading cause of global burden from skin disease affecting all ages.
  - reference: PMID:28846349
    reference_title: Atopic Dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AD has significant morbidity and it appears that the prevalence of the disorder has been increasing over the past few decades."
    explanation: Confirms increasing prevalence trend of atopic dermatitis.
pathophysiology:
- name: Epidermal Barrier Dysfunction
  description: Loss-of-function mutations in filaggrin (FLG) and other barrier proteins lead to impaired skin barrier integrity, increased transepidermal water loss, and enhanced allergen penetration. This is the primary initiating event in many patients.
  genes:
  - preferred_term: FLG
    term:
      id: hgnc:3748
      label: FLG
  biological_processes:
  - preferred_term: Keratinization
    term:
      id: GO:0031424
      label: keratinization
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  evidence:
  - reference: PMID:16550169
    reference_title: "Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Filaggrin is a key protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Here we show that two independent loss-of-function genetic variants (R510X [sic, correct designation is R501X] and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis.
    explanation: Landmark study establishing FLG loss-of-function as the strongest genetic risk factor for atopic dermatitis, with ~9% carrier frequency in Europeans.
  - reference: PMID:21388665
    reference_title: "Contrasting pathogenesis of atopic dermatitis and psoriasis--part I: clinical and pathologic concepts."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: They are similar in that they are complex inherited diseases involving genes that encode immune components and structural proteins that regulate differentiation of epidermal cells. Each disease is characterized by proliferation of epidermal keratinocytes and abnormal cornification or terminal differentiation in the epidermis
    explanation: Describes the epidermal barrier dysfunction in atopic dermatitis including abnormal cornification and keratinocyte differentiation.
- name: Type 2 Immune Response
  description: Th2-skewed immune response drives the hallmark inflammation. IL-4, IL-13, and IL-31 promote IgE production, eosinophil recruitment, and pruritus. IL-4/IL-13 signaling through JAK1/STAT6 further impairs barrier function by downregulating filaggrin and other barrier proteins.
  genes:
  - preferred_term: IL4
    term:
      id: hgnc:6014
      label: IL4
  - preferred_term: IL13
    term:
      id: hgnc:5973
      label: IL13
  - preferred_term: IL31
    term:
      id: hgnc:19372
      label: IL31
  - preferred_term: STAT6
    term:
      id: hgnc:11368
      label: STAT6
  downstream:
  - target: Epidermal Barrier Dysfunction
    description: IL-4 and IL-13 downregulate filaggrin expression, creating a vicious cycle of barrier disruption and immune activation.
  - target: Pruritogen-Induced Neuronal Activation
    description: IL-31 signaling contributes to neuronal itch signaling in lesional skin.
  biological_processes:
  - preferred_term: Type 2 immune response
    term:
      id: GO:0042092
      label: type 2 immune response
  - preferred_term: T-helper 2 cell differentiation
    term:
      id: GO:0045064
      label: T-helper 2 cell differentiation
  - preferred_term: Interleukin-4-mediated signaling pathway
    term:
      id: GO:0035771
      label: interleukin-4-mediated signaling pathway
  - preferred_term: IgE isotype switching
    term:
      id: GO:0035708
      label: interleukin-4-dependent isotype switching to IgE isotypes
  cell_types:
  - preferred_term: T-helper 2 cell
    term:
      id: CL:0000546
      label: T-helper 2 cell
  - preferred_term: Group 2 innate lymphoid cell
    term:
      id: CL:0001069
      label: group 2 innate lymphoid cell
  - preferred_term: Eosinophil
    term:
      id: CL:0000771
      label: eosinophil
  - preferred_term: Mast cell
    term:
      id: CL:0000097
      label: mast cell
  evidence:
  - reference: PMID:30819278
    reference_title: "Pathophysiology of atopic dermatitis: Clinical implications."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type 2 cytokines as well as interleukin 17 and interleukin 22 contribute to skin barrier dysfunction and the development of AD.
    explanation: Confirms the role of type 2 cytokines in AD pathophysiology and their contribution to barrier dysfunction, supporting the Th2/type 2 immune mechanism.
  - reference: PMID:21388665
    reference_title: "Contrasting pathogenesis of atopic dermatitis and psoriasis--part I: clinical and pathologic concepts."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: skin lesions contain immune infiltrates of T cells, dendritic cells, and other types of leukocytes. We review similarities between the diseases and differences in epidermal barrier defects and immune cells.
    explanation: Describes the immune cell infiltrates in AD lesions including T cells and dendritic cells, consistent with type 2 immune response.
- name: TOPK-STAT3 Signaling Axis
  description: T-Lymphokine-Activated Killer Cell-Originated Protein Kinase (TOPK) is upregulated in AD and directly phosphorylates STAT3 at Ser727 in keratinocytes and mast cells, driving the production of inflammatory cytokines (IL-6, IL-8, IL-33) and IgE dysregulation. This axis acts as an amplifier of the type 2 immune response.
  genes:
  - preferred_term: PBK
    term:
      id: hgnc:18282
      label: PBK
  - preferred_term: STAT3
    term:
      id: hgnc:11364
      label: STAT3
  biological_processes:
  - preferred_term: Protein phosphorylation
    term:
      id: GO:0006468
      label: protein phosphorylation
  - preferred_term: Interleukin-6 production
    term:
      id: GO:0032635
      label: interleukin-6 production
  - preferred_term: Interleukin-8 production
    term:
      id: GO:0032637
      label: interleukin-8 production
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: Mast cell
    term:
      id: CL:0000097
      label: mast cell
  downstream:
  - target: Type 2 Immune Response
    description: TOPK-mediated STAT3 Ser727 phosphorylation amplifies IL-6 and IL-8 production, enhancing Th2 polarization and IgE responses.
  - target: Secondary Inflammatory Amplification
    description: TOPK-STAT3 signaling perpetuates keratinocyte and mast cell inflammatory output, sustaining chronic lesion inflammation.
  evidence:
  - reference: PMID:42237026
    reference_title: "Targeting the TOPK-STAT3 pathway in keratinocytes and mast cells mediates the therapeutic attenuation of Atopic dermatitis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
    explanation: Establishes TOPK-STAT3 Ser727 phosphorylation as the direct mechanistic driver of inflammatory responses in AD-relevant cell types.
  - reference: PMID:42237026
    reference_title: "Targeting the TOPK-STAT3 pathway in keratinocytes and mast cells mediates the therapeutic attenuation of Atopic dermatitis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Genetic or pharmacological inhibition of TOPK markedly attenuated AD-like pathological features and reduces the levels of IgE, IL-6, IL-8 and IL-33"
    explanation: Demonstrates that TOPK inhibition reduces multiple AD-associated inflammatory mediators and IgE dysregulation.
- name: Th17/Th22 Inflammation
  description: In addition to the dominant Th2 response, Th17 and Th22 cells contribute to inflammation, particularly in acute lesions and Asian patients. IL-17 and IL-22 further disrupt epidermal differentiation.
  biological_processes:
  - preferred_term: T-helper 17 type immune response
    term:
      id: GO:0072538
      label: T-helper 17 type immune response
  cell_types:
  - preferred_term: T-helper 17 cell
    term:
      id: CL:0000899
      label: T-helper 17 cell
- name: TOPK-STAT3 Signaling Axis
  description: >-
    TOPK (T-Lymphokine-Activated Killer cell-Originated Protein Kinase) is
    upregulated in atopic dermatitis lesions and directly phosphorylates STAT3
    at Ser727 in keratinocytes and mast cells, amplifying inflammatory
    responses including IL-6, IL-8, and IL-33 production. TOPK-driven STAT3
    activation contributes to the maintenance of AD-associated inflammation.
  genes:
  - preferred_term: PBK
    term:
      id: hgnc:18282
      label: PBK
  - preferred_term: STAT3
    term:
      id: hgnc:11364
      label: STAT3
  downstream:
  - target: Secondary Inflammatory Amplification
    description: TOPK-mediated STAT3 Ser727 phosphorylation drives IL-6, IL-8, and IL-33 production, amplifying chronic skin inflammation.
  biological_processes:
  - preferred_term: Cytokine production
    term:
      id: GO:0001816
      label: cytokine production
  - preferred_term: Signal transduction
    term:
      id: GO:0007165
      label: signal transduction
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: Mast cell
    term:
      id: CL:0000097
      label: mast cell
  evidence:
  - reference: PMID:42237026
    reference_title: Targeting the TOPK-STAT3 pathway in keratinocytes and mast cells mediates the therapeutic attenuation of Atopic dermatitis.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Bioinformatics analysis revealed that TOPK was significantly upregulated in AD patients."
    explanation: GEO database bioinformatics analysis establishes TOPK upregulation in AD patient transcriptomes.
  - reference: PMID:42237026
    reference_title: Targeting the TOPK-STAT3 pathway in keratinocytes and mast cells mediates the therapeutic attenuation of Atopic dermatitis.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Genetic or pharmacological inhibition of TOPK markedly attenuated AD-like pathological features and reduces the levels of IgE, IL-6, IL-8 and IL-33, suggesting that TOPK contributes to AD pathogenesis."
    explanation: Animal model demonstrates TOPK's functional contribution to AD-like inflammatory pathology and cytokine production.
  - reference: PMID:42237026
    reference_title: Targeting the TOPK-STAT3 pathway in keratinocytes and mast cells mediates the therapeutic attenuation of Atopic dermatitis.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
    explanation: Defines the TOPK-STAT3 Ser727 phosphorylation mechanism in keratinocytes and mast cells, the key cellular sources of the AD inflammatory axis.
- name: Pruritogen-Induced Neuronal Activation
  description: IL-31 and other pruritogens activate cutaneous sensory neurons, generating persistent itch in atopic dermatitis.
  genes:
  - preferred_term: IL31
    term:
      id: hgnc:19372
      label: IL31
  downstream:
  - target: Scratching-Induced Barrier Injury
    description: Persistent itch drives repetitive scratching behavior.
  cell_types:
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  evidence:
  - reference: PMID:30819278
    reference_title: "Pathophysiology of atopic dermatitis: Clinical implications."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: New insights into the pathophysiology of AD have focused on epidermal lipid profiles, neuroimmune interactions, and microbial dysbiosis.
    explanation: Supports neuroimmune signaling as a component of AD pathophysiology.
- name: Scratching-Induced Barrier Injury
  description: Repetitive scratching causes mechanical skin injury and worsens epidermal barrier dysfunction.
  downstream:
  - target: Secondary Inflammatory Amplification
    description: Mechanical barrier injury increases local inflammatory activation.
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
- name: Secondary Inflammatory Amplification
  description: Barrier injury from scratching perpetuates inflammatory signaling and contributes to chronic lesion persistence.
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
phenotypes:
- name: Eczematoid Dermatitis
  category: Dermatological
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Erythematous, pruritic patches and plaques with scaling, often in flexural areas.
  phenotype_term:
    preferred_term: Eczematoid dermatitis
    term:
      id: HP:0000964
      label: Eczematoid dermatitis
  evidence:
  - reference: PMID:28846349
    reference_title: "Atopic Dermatitis."
    supports: SUPPORT
    snippet: "This chronic disorder associated with pruritus usually starts in infancy and presents with dry skin, eczematous lesions and lichenification."
    explanation: Eczematous lesions are a defining feature of atopic dermatitis.
- name: Pruritus
  category: Dermatological
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Intense itching is the hallmark symptom, often worse at night.
  phenotype_term:
    preferred_term: Pruritus
    term:
      id: HP:0000989
      label: Pruritus
  evidence:
  - reference: PMID:39659858
    reference_title: "Atopic Dermatitis: A Review of Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "Atopic dermatitis, more commonly known as atopic eczema, is a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus."
    explanation: Intense pruritus is a defining clinical characteristic of atopic dermatitis.
- name: Xerosis
  category: Dermatological
  frequency: VERY_FREQUENT
  notes: Generalized dry skin reflecting barrier dysfunction.
  phenotype_term:
    preferred_term: Xerosis
    term:
      id: HP:0000958
      label: Dry skin
  evidence:
  - reference: PMID:39659858
    reference_title: "Atopic Dermatitis: A Review of Diagnosis and Treatment."
    supports: SUPPORT
    snippet: "Atopic dermatitis, more commonly known as atopic eczema, is a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus."
    explanation: Dry skin (xerosis) is a defining clinical characteristic of atopic dermatitis reflecting barrier dysfunction.
- name: Elevated Serum IgE
  category: Immunological
  frequency: FREQUENT
  notes: Present in extrinsic subtype (~80% of patients).
  phenotype_term:
    preferred_term: Elevated serum IgE
    term:
      id: HP:0003212
      label: Increased circulating IgE concentration
  evidence:
  - reference: PMID:20207111
    reference_title: "Extrinsic and intrinsic types of atopic dermatitis."
    supports: SUPPORT
    snippet: "Extrinsic or allergic AD shows high total serum IgE levels and the presence of specific IgE for environmental and food allergens... While extrinsic AD is the classical type with high prevalence, the incidence of intrinsic AD is approximately 20%"
    explanation: Approximately 80% of atopic dermatitis patients have the extrinsic subtype characterized by elevated serum IgE levels.
- name: Erythema
  category: Dermatological
  frequency: VERY_FREQUENT
  notes: Erythematous patches and plaques are a core clinical feature, often
    the earliest visible sign of active disease.
  phenotype_term:
    preferred_term: Erythema
    term:
      id: HP:0010783
      label: Erythema
  evidence:
  - reference: PMID:39659858
    reference_title: "Atopic Dermatitis: A Review of Diagnosis and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a chronic, relapsing inflammatory skin disorder characterized by dry skin, localized erythematous rash, and intense pruritus"
    explanation: Erythematous rash is listed as one of the three cardinal features of atopic dermatitis.
- name: Flexural Lichenification
  category: Dermatological
  frequency: FREQUENT
  notes: Lichenification preferentially affects flexural areas (antecubital
    and popliteal fossae, neck) and is a hallmark distribution pattern.
    Thickened, leathery skin develops from chronic scratching.
  phenotype_term:
    preferred_term: Flexural lichenification
    term:
      id: HP:0007453
      label: Flexural lichenification
  evidence:
  - reference: PMID:28846349
    reference_title: Atopic Dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This chronic disorder associated with pruritus usually starts in infancy and presents with dry skin, eczematous lesions and lichenification."
    explanation: Lichenification is a defining chronic feature of atopic dermatitis.
  - reference: PMID:35297082
    reference_title: Differences between pediatric and adult atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Core AD features are similar between children and adults overall, including lesions affecting flexural areas, presence of atopy, and xerosis."
    explanation: Flexural distribution is identified as a core feature of atopic dermatitis across age groups.
- name: Recurrent Skin Infections
  category: Dermatological
  frequency: FREQUENT
  notes: Compromised barrier function and immune dysregulation predispose to
    bacterial (S. aureus), viral (HSV, molluscum), and fungal skin infections.
  phenotype_term:
    preferred_term: Recurrent skin infections
    term:
      id: HP:0001581
      label: Recurrent skin infections
  evidence:
  - reference: PMID:31755570
    reference_title: "Disseminated bullous impetigo and atopic dermatitis: Case series and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Due to compromised barrier function and immune dysregulation, children with atopic dermatitis (AD) are at increased risk of cutaneous infections"
    explanation: Establishes that barrier dysfunction and immune dysregulation in AD lead to increased risk of cutaneous infections.
  - reference: PMID:35490395
    reference_title: "An integrated analysis of herpes virus infections from eight randomized clinical studies of baricitinib in adults with moderate-to-severe atopic dermatitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic dermatitis (AD) is associated with an increased risk for viral infections including those caused by herpes simplex virus and varicella zoster virus."
    explanation: Confirms increased susceptibility to viral skin infections in AD patients.
- name: Sleep Disturbance
  category: Neuropsychiatric
  frequency: FREQUENT
  notes: Pruritus-driven sleep disruption is a major contributor to reduced
    quality of life, with severity correlating with disease activity.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:38864389
    reference_title: "Exploring the interplay of atopic dermatitis severity with sleep and mental health: a case-control study in adult patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AD patients reported lower sleep quality (p = 0.002), more severe insomnia (p = 0.006) and depression (p = 0.013), and higher stress levels than healthy adults (p = 0.049)."
    explanation: Case-control study demonstrating significantly impaired sleep quality and increased insomnia in AD patients compared to matched controls.
- name: Dennie-Morgan Infraorbital Folds
  category: Dermatological
  frequency: FREQUENT
  notes: Dennie-Morgan folds are prominent infraorbital creases characteristic
    of atopic dermatitis, more common in children. Present in both extrinsic
    and intrinsic subtypes.
  phenotype_term:
    preferred_term: Dennie-Morgan infraorbital folds
    term:
      id: HP:0000607
      label: Periorbital wrinkles
  evidence:
  - reference: PMID:35297082
    reference_title: Differences between pediatric and adult atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "children with AD have more exudative lesions, perifollicular accentuation, pityriasis alba, Dennie-Morgan folds, and seborrheic dermatitis-like presentation."
    explanation: Dennie-Morgan folds (infraorbital creases associated with periorbital hyperpigmentation) are identified as a characteristic pediatric AD feature.
  - reference: PMID:20207111
    reference_title: Extrinsic and intrinsic types of atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical features of intrinsic AD include relative late onset, milder severity, and Dennie-Morgan folds, but no ichthyosis vulgris or palmar hyperlinearity."
    explanation: Dennie-Morgan folds are present across both extrinsic and intrinsic AD subtypes.
- name: Keratosis Pilaris
  category: Dermatological
  frequency: OCCASIONAL
  notes: Follicular keratotic papules on extensor surfaces, associated with
    filaggrin-related barrier dysfunction and ichthyosis vulgaris.
  phenotype_term:
    preferred_term: Keratosis pilaris
    term:
      id: HP:0032152
      label: Keratosis pilaris
  evidence:
  - reference: PMID:31536314
    reference_title: Keratosis Pilaris.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Keratosis pilaris is associated with many other conditions, including atopic dermatitis, ichthyosis vulgaris, obesity, diabetes mellitus, and malnutrition."
    explanation: StatPearls reference directly identifies atopic dermatitis as one of the conditions associated with keratosis pilaris.
- name: Food Allergy
  category: Immunological
  frequency: FREQUENT
  notes: A common comorbidity, particularly in early-onset and severe AD.
    Part of the atopic march in a subset of patients. Epicutaneous
    sensitization through the disrupted skin barrier may drive food allergy
    development.
  phenotype_term:
    preferred_term: Food allergy
    term:
      id: HP:0500093
      label: Food allergy
  evidence:
  - reference: PMID:32738956
    reference_title: Atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
    explanation: Lancet 2020 review identifies food allergy as a major AD comorbidity.
  - reference: PMID:28846349
    reference_title: Atopic Dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AD is associated with other IgE associated disorders like allergic rhinitis, asthma, and food allergies."
    explanation: Confirms the well-established association between AD and food allergies as IgE-mediated comorbidities.
- name: Allergic Rhinitis
  category: Immunological
  frequency: FREQUENT
  notes: A common atopic comorbidity, often developing after the onset of AD
    as part of the atopic march in some patients.
  phenotype_term:
    preferred_term: Allergic rhinitis
    term:
      id: HP:0003193
      label: Allergic rhinitis
  evidence:
  - reference: PMID:32738956
    reference_title: Atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
    explanation: Lancet 2020 review identifies allergic rhinitis as a major AD comorbidity.
  - reference: PMID:35297082
    reference_title: Differences between pediatric and adult atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic diseases commonly co-occur with AD, although most do not temporally have the \"atopic march.\""
    explanation: Confirms atopic comorbidities co-occur with AD, while noting that the temporal sequence of the atopic march is not universal.
- name: Asthma
  category: Immunological
  frequency: FREQUENT
  notes: A major atopic comorbidity. Part of the classic atopic triad
    alongside allergic rhinitis. Epicutaneous sensitization through the
    disrupted skin barrier may contribute to airway sensitization.
  phenotype_term:
    preferred_term: Asthma
    term:
      id: HP:0002099
      label: Asthma
  evidence:
  - reference: PMID:32738956
    reference_title: Atopic dermatitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders."
    explanation: Lancet 2020 review identifies asthma as a major AD comorbidity.
  - reference: PMID:30819278
    reference_title: "Pathophysiology of atopic dermatitis: Clinical implications."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An impaired skin barrier may be the initial step in the development of the atopic march as well as AD, which leads to further skin inflammation and allergic sensitization."
    explanation: Links impaired skin barrier in AD to the development of the atopic march, including progression to asthma.
genetic:
- name: FLG
  association: Associated
  notes: Loss-of-function variants are the strongest genetic risk factor. R501X and 2282del4 are common in European populations.
  evidence:
  - reference: PMID:16550169
    reference_title: "Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: two independent loss-of-function genetic variants (R510X [sic, correct designation is R501X] and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis. These variants are carried by approximately 9% of people of European origin.
    explanation: Landmark Palmer et al. 2006 study establishing FLG loss-of-function as the major genetic predisposing factor for atopic dermatitis.
- name: IL4R
  association: Associated
  notes: Variants in IL-4 receptor alpha chain affect Th2 signaling intensity.
- name: IL13
  association: Associated
  notes: Variants affecting IL-13 expression or function.
- name: STAT6
  association: Associated
  notes: Transcription factor downstream of IL-4/IL-13 signaling.
- name: EMSY
  association: Associated
  notes: Chromatin remodeling factor identified in GWAS.
- name: BACH2
  association: GWAS
  notes: Transcription factor regulating Treg/effector T cell balance and B cell class switching
- name: TNFAIP3
  association: GWAS
  notes: Encodes A20, a ubiquitin-editing enzyme that negatively regulates NF-kB signaling
- name: EGR2
  association: GWAS
  notes: Transcription factor involved in T cell anergy and peripheral tolerance
- name: ETS1
  association: GWAS
  notes: Transcription factor regulating T and B cell development and immune cell differentiation
- name: IRF4
  association: GWAS
  notes: Transcription factor essential for Th17 and Th2 cell differentiation and plasma cell development
- name: SATB1
  association: GWAS
  notes: Chromatin organizer regulating T cell development and lineage commitment
- name: SMAD3
  association: GWAS
  notes: TGF-beta signaling mediator regulating T cell differentiation and immune tolerance
- name: REL
  association: GWAS
  notes: NF-kB subunit c-Rel controlling lymphocyte activation and survival
environmental:
- name: Allergen Exposure
  description: House dust mites, pet dander, and pollens can trigger or exacerbate disease.
  effect: TRIGGERS
- name: Skin Irritants
  description: Soaps, detergents, and harsh fabrics disrupt the already compromised barrier.
  effect: TRIGGERS
- name: Microbial Dysbiosis
  description: Staphylococcus aureus colonization is found in >90% of lesional skin and amplifies inflammation through superantigens and biofilm formation.
  effect: WORSENS
treatments:
- name: Emollients and Moisturizers
  description: First-line treatment to restore skin barrier function and reduce transepidermal water loss.
- name: Topical Corticosteroids
  description: First-line anti-inflammatory treatment for flares, applied to affected areas.
- name: Dupilumab
  description: Monoclonal antibody targeting IL-4 receptor alpha, blocking both IL-4 and IL-13 signaling. FDA-approved for moderate-to-severe atopic dermatitis.
  treatment_term:
    preferred_term: biologic therapy
    term:
      id: NCIT:C15262
      label: Immunotherapy
    therapeutic_agent:
    - preferred_term: dupilumab
      term:
        id: NCIT:C162455
        label: Dupilumab
- name: JAK Inhibitors
  description: Oral (baricitinib, upadacitinib, abrocitinib) and topical (ruxolitinib) JAK inhibitors targeting the JAK-STAT pathway downstream of type 2 cytokines.
  treatment_term:
    preferred_term: JAK inhibitor therapy
    term:
      id: MAXO:0000297
      label: immune suppressant agent therapy
- name: Phototherapy
  description: Narrowband UVB phototherapy for moderate-to-severe disease.
- name: TOPK Inhibitors
  description: Small-molecule inhibitors of TOPK (PBK) that target the TOPK-STAT3 signaling axis in keratinocytes and mast cells. Pharmacological or genetic TOPK inhibition attenuates AD-like pathological features and reduces inflammatory cytokine levels (IL-6, IL-8, IL-33, IgE).
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: TOPK-STAT3 Signaling Axis
    description: TOPK inhibitors block TOPK-mediated STAT3 Ser727 phosphorylation and downstream inflammatory cytokine production.
discussions:
- discussion_id: gap_ad_topk_stat3_axis
  prompt: >-
    TOPK (PBK) is upregulated in atopic dermatitis and its inhibition attenuates
    AD-like inflammation via STAT3 Ser727 phosphorylation in keratinocytes and
    mast cells, but is TOPK-STAT3 signaling a primary causal driver of AD
    pathogenesis or a downstream amplifier of the established type 2 / barrier
    circuit, what is its dominant in vivo cellular source, and does the axis
    translate from cell and mouse models to human disease?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Type 2 Immune Response
  - pathophysiology#Epidermal Barrier Dysfunction
  - pathophysiology#Secondary Inflammatory Amplification
  rationale: >-
    Atopic dermatitis pathogenesis is well characterized at the level of
    epidermal barrier dysfunction and the IL-4/IL-13/IL-31 type 2 immune program
    signaling through JAK1/STAT6, which underpins approved biologic and JAK-
    inhibitor therapies. Recent work identifies T-LAK-cell-originated protein
    kinase (TOPK) as upregulated in AD lesions, where it directly interacts with
    and phosphorylates STAT3 at Ser727 in HaCaT keratinocytes and mast cells, and
    where genetic or pharmacologic TOPK inhibition reduces IgE, IL-6, IL-8, and
    IL-33 and attenuates AD-like features. What remains unresolved is the causal
    placement of this TOPK-STAT3 axis: whether it initiates inflammation upstream
    of, runs in parallel to, or is induced by the canonical type 2 and barrier
    pathways, and whether STAT3 Ser727 signaling acts mainly in keratinocytes,
    mast cells, or other resident/infiltrating cells in intact skin. The current
    evidence rests largely on cell lines, bioinformatic (GEO) profiling, and a
    disease model, so the human translational relevance and therapeutic window of
    TOPK inhibition relative to existing STAT6/JAK-directed therapies is unknown.
  proposed_experiments:
  - experiment_id: exp_ad_topk_stat3_epistasis
    name: Cell-type-resolved epistasis of the TOPK-STAT3 axis versus the type 2 barrier circuit
    description: >-
      Use cell-type-conditional TOPK loss- and gain-of-function in barrier and
      immune compartments of AD models, combined with epistasis against IL-4/
      IL-13 (type 2) and barrier perturbations and STAT3 Ser727 phospho-readouts,
      to place TOPK-STAT3 in the causal hierarchy and identify the dominant in
      vivo cellular source. Cross-validate against human AD skin to test
      translational relevance.
    experiment_type:
      preferred_term: cell-type-conditional perturbation and epistasis study
    readouts:
    - name: STAT3 Ser727 phosphorylation by compartment
      target: pathophysiology#Secondary Inflammatory Amplification
      description: >-
        Quantify STAT3 Ser727 phosphorylation in keratinocytes versus mast cells
        and other skin-resident cells under TOPK perturbation to localize the
        active signaling compartment.
      assays:
      - preferred_term: phospho-specific immunostaining
      - preferred_term: phosphoproteomic profiling
      direction: POSITIVE
    - name: Type 2 cytokine and barrier dependence
      target: pathophysiology#Type 2 Immune Response
      description: >-
        Test whether TOPK-driven inflammation persists when IL-4/IL-13 signaling
        is blocked, distinguishing an upstream/parallel driver from a type 2-
        dependent amplifier.
      assays:
      - preferred_term: cytokine quantification
      direction: NEGATIVE
    - name: Barrier integrity response to TOPK modulation
      target: pathophysiology#Epidermal Barrier Dysfunction
      description: >-
        Measure transepidermal water loss and barrier protein expression after
        TOPK inhibition to determine whether the axis modifies barrier function
        directly or only via inflammation.
      assays:
      - preferred_term: transepidermal water loss measurement
      direction: NEGATIVE
    decision_criterion: >-
      TOPK-STAT3 is supported as a primary driver if compartment-conditional TOPK
      loss reduces AD-like inflammation independently of (and upstream of) intact
      IL-4/IL-13 signaling, with the dominant active STAT3 Ser727 compartment
      reproducibly identified and the axis detectable in human AD skin; it is a
      downstream amplifier if its effects require an intact type 2 circuit.
    would_support:
    - pathophysiology#Type 2 Immune Response
    - pathophysiology#Secondary Inflammatory Amplification
    - pathophysiology#Epidermal Barrier Dysfunction
  evidence:
  - reference: PMID:42237026
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "T-Lymphokine-Activated Killer Cell-Originated Protein Kinase (TOPK) is known to promote inflammation, its specific role in AD remains unclear."
    explanation: >-
      Establishes that TOPK is implicated in inflammation but its specific
      mechanistic role in atopic dermatitis is unresolved, motivating the gap.
  - reference: PMID:42237026
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TOPK was found to directly interact with and phosphorylate STAT3 at Ser727. Inhibition of TOPK in both HaCaT keratinocytes and mast cells decreased STAT3 phosphorylation at Ser727, thereby alleviating AD-related inflammatory responses."
    explanation: >-
      Defines the proposed TOPK-STAT3 Ser727 mechanism in keratinocytes and mast
      cells, the candidate axis whose causal placement and cellular source the
      gap seeks to resolve.
disease_term:
  preferred_term: atopic dermatitis
  term:
    id: MONDO:0004980
    label: atopic eczema
references:
- reference: DOI:10.1007/s13555-025-01352-y
  title: 'Interleukin-4 and Atopic Dermatitis: Why Does it Matter? A Narrative Review'
  findings: []
- reference: DOI:10.1038/s41467-023-41857-8
  title: Multifaceted analysis of cross-tissue transcriptomes reveals phenotype–endotype associations in atopic dermatitis
  findings: []
- reference: DOI:10.1126/sciimmunol.abi6887
  title: IL-31–dependent neurogenic inflammation restrains cutaneous type 2 immune response in allergic dermatitis
  findings: []
- reference: DOI:10.1186/s43556-025-00313-3
  title: 'Atopic dermatitis: diagnosis, molecular pathogenesis, and therapeutics'
  findings: []
- reference: DOI:10.14789/ejmj.jmj24-0036-r
  title: Mechanisms of Itch in Atopic Dermatitis
  findings: []
- reference: DOI:10.3390/jcm12041538
  title: 'The Role of Tight Junctions in Atopic Dermatitis: A Systematic Review'
  findings: []
- reference: DOI:10.3390/jcm14145053
  title: 'Anti-Inflammatory Therapies for Atopic Dermatitis: A New Era in Targeted Treatment'
  findings: []
- reference: DOI:10.64898/2026.01.10.26343854
  title: 'Protective and Susceptibility Clusters of Environmental Factors, Gene Expression, Antibody Responses, and Cytokines in Pediatric Atopic Dermatitis: Insights from Multi-Modal Data Integration'
  findings: []
- reference: DOI:10.7759/cureus.86937
  title: 'Skin Barrier Dysfunction in Chronic Dermatoses: From Pathophysiology to Emerging Therapeutic Strategies'
  findings: []
📚

References & Deep Research

References

9
DOI:10.1007/s13555-025-01352-y
Interleukin-4 and Atopic Dermatitis: Why Does it Matter? A Narrative Review
No top-level findings curated for this source.
DOI:10.1038/s41467-023-41857-8
Multifaceted analysis of cross-tissue transcriptomes reveals phenotype–endotype associations in atopic dermatitis
No top-level findings curated for this source.
DOI:10.1126/sciimmunol.abi6887
IL-31–dependent neurogenic inflammation restrains cutaneous type 2 immune response in allergic dermatitis
No top-level findings curated for this source.
DOI:10.1186/s43556-025-00313-3
Atopic dermatitis: diagnosis, molecular pathogenesis, and therapeutics
No top-level findings curated for this source.
DOI:10.14789/ejmj.jmj24-0036-r
Mechanisms of Itch in Atopic Dermatitis
No top-level findings curated for this source.
DOI:10.3390/jcm12041538
The Role of Tight Junctions in Atopic Dermatitis: A Systematic Review
No top-level findings curated for this source.
DOI:10.3390/jcm14145053
Anti-Inflammatory Therapies for Atopic Dermatitis: A New Era in Targeted Treatment
No top-level findings curated for this source.
DOI:10.64898/2026.01.10.26343854
Protective and Susceptibility Clusters of Environmental Factors, Gene Expression, Antibody Responses, and Cytokines in Pediatric Atopic Dermatitis: Insights from Multi-Modal Data Integration
No top-level findings curated for this source.
DOI:10.7759/cureus.86937
Skin Barrier Dysfunction in Chronic Dermatoses: From Pathophysiology to Emerging Therapeutic Strategies
No top-level findings curated for this source.

Deep Research

2
Disorder ▸

Disorder

  • Name: Atopic Dermatitis
  • Category: Complex
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 15

Key Pathophysiology Nodes

  • Epidermal Barrier Dysfunction
  • Type 2 Immune Response
  • Th17/Th22 Inflammation
  • Pruritogen-Induced Neuronal Activation
  • Scratching-Induced Barrier Injury
  • Secondary Inflammatory Amplification
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1007/s13555-025-01352-y
  • DOI:10.1038/s41467-023-41857-8
  • DOI:10.1126/sciimmunol.abi6887
  • DOI:10.1186/s43556-025-00313-3
  • DOI:10.14789/ejmj.jmj24-0036-r
  • DOI:10.3390/jcm12041538
  • DOI:10.3390/jcm14145053
  • DOI:10.64898/2026.01.10.26343854
  • DOI:10.7759/cureus.86937
Falcon ▸
Disease Pathophysiology Research Report
Edison Scientific Literature 26 citations 2026-02-14T17:00:30.185672

Disease Pathophysiology Research Report

Target Disease - Disease Name: Atopic Dermatitis (AD) - MONDO ID: MONDO:0004994 - Category: Complex

Pathophysiology description (current understanding, 2023–2025 emphasis) Atopic dermatitis is a chronic, relapsing inflammatory dermatosis driven by the interplay of epidermal barrier dysfunction, type 2–skewed immunity, neuroimmune pruritus circuitry, and microbial/ environmental exposures. Barrier failure (filaggrin insufficiency, altered ceramide composition, and tight-junction defects) permits enhanced allergen/microbe ingress and promotes alarmin release, which activates dendritic cells and ILC2/Th2 axes. IL-4/IL-13 signaling amplifies inflammation and further downregulates barrier genes, establishing feed-forward loops. Pruritus is sustained by neuroimmune mediators—especially IL-31—signaling to TRP channel–bearing sensory afferents and, in chronic exposure, engaging a paradoxical neurogenic anti–type 2 brake via CGRP. JAK–STAT integrates many of these cytokine signals and is a validated therapeutic hub. Multi-omics studies reveal clinically relevant endotypes aligning cutaneous and blood transcriptomes with phenotypes and treatment trajectories. Therapeutically, targeting IL-4/IL-13 (dupilumab; IL-13 inhibitors) and JAK1/2 pathways improves disease activity and, in some studies, barrier function, supporting causal roles for these axes in AD. (katsarou2023theroleof pages 12-12, kamata2025mechanismsofitch pages 2-4, torres2025interleukin4andatopic pages 14-15, urzua2025skinbarrierdysfunction pages 3-4, bai2025atopicdermatitisdiagnosis pages 25-26, zhakparov2026protectiveandsusceptibility pages 22-23)

Key concepts and definitions (with recent sources) - Epidermal barrier dysfunction: Tight junction (TJ) impairment (e.g., reduced claudin-1) and filaggrin deficiency increase permeability and trans-epidermal water loss, facilitating allergen and pathogen entry; Th2 cytokines suppress TJ proteins. Quote: “Impaired TJ barrier function and skin permeability in AD lesions is correlated with cldn-1 levels. Th2 inflammation inhibits the expression of cldn-1 and cldn-23” (Feb 2023, Journal of Clinical Medicine; URL: https://doi.org/10.3390/jcm12041538). (katsarou2023theroleof pages 12-12) - Type 2 cytokine axis: IL-4 and IL-13 orchestrate barrier disruption, dysbiosis, pruritus, and inflammation in AD. Narrative review emphasis: “IL-4 plays a critical role in skin barrier dysfunction, dysbiosis, pruritus, and inflammation” (Feb 2025, Dermatology and Therapy; URL: https://doi.org/10.1007/s13555-025-01352-y). (torres2025interleukin4andatopic pages 14-15) - Neuroimmune itch (IL-31 axis): IL-31 acts directly on pruritoceptors (IL31RA/OSMR) to induce itch and neurite outgrowth and is a central mediator of AD pruritus. Quote: “IL-31 directly induces pruritus… and selectively promotes nerve fiber extension in these neurons” (Jan 2025, Juntendo Medical Journal; URL: https://doi.org/10.14789/ejmj.jmj24-0036-r). (kamata2025mechanismsofitch pages 2-4) - Neurogenic restraint of type 2 inflammation: In chronic allergen exposure, IL-31 activation of sensory neurons can trigger CGRP release that suppresses Th2 responses, providing a mechanistic basis for paradoxical flares with anti–IL-31 receptor therapy. Quote: “IL-31… restrains cutaneous type 2 inflammation… IL-31 activation of IL31RA+ pruritoceptors triggers release of calcitonin gene-related protein (CGRP), which… inhibit[s] CD4+ T cell proliferation and reduce[s]… IL-13” (Oct 2023, Science Immunology; URL: https://doi.org/10.1126/sciimmunol.abi6887). (bai2025atopicdermatitisdiagnosis pages 25-26) - JAK–STAT as hub pathway: Many AD cytokines signal via JAKs; clinical efficacy of oral and topical JAK inhibitors supports centrality of this pathway (reviewed 2025). (urzua2025skinbarrierdysfunction pages 3-4) - Molecular endotypes: Integrated skin and blood transcriptomics uncover endotype–phenotype associations and clusters aligned with severity and trajectories, enabling personalized monitoring. (Oct 2023, Nature Communications; URL: https://doi.org/10.1038/s41467-023-41857-8). (bilinski2025antiinflammatorytherapiesfor pages 2-4)

1) Core Pathophysiology - Primary mechanisms - Barrier failure: FLG deficiency and TJ defects (e.g., CLDN1) lead to increased permeability; scratching worsens claudin-1 loss and barrier leak. Th2 cytokines (IL-4/IL-13) suppress claudins and barrier proteins, coupling immunity to barrier pathology (Feb 2023; URL above). (katsarou2023theroleof pages 12-12) - Epithelial alarmins: Barrier stress releases TSLP/IL-33/IL-25 from keratinocytes, priming DCs/ILC2/Th2; their role is integrated within itch reviews and type 2 discussions (2025; URLs below). (kamata2025mechanismsofitch pages 2-4, torres2025interleukin4andatopic pages 14-15) - Type 2 immunity: IL-4/IL-13 drive IgE class switching, eosinophilia, keratinocyte chemokine production, and barrier gene suppression. (torres2025interleukin4andatopic pages 14-15, urzua2025skinbarrierdysfunction pages 3-4) - Neuroimmune itch: IL-31→IL31RA/OSMR on TRPV1/TRPA1+ small-diameter afferents; neuronal plasticity (hyperinnervation) correlates with itch; Sema3A↓ and NGF↑ alter epidermal innervation in AD (Jan 2025; URL below). (kamata2025mechanismsofitch pages 2-4) - Neurogenic restraint loop: IL-31–induced CGRP limits Th2 cell accumulation and IL-13 output in chronic allergen dermatitis (Oct 2023; URL below). (bai2025atopicdermatitisdiagnosis pages 25-26) - JAK–STAT integration: Many cytokines (IL-4/IL-13/IL-31/TSLP) signal through JAK1/2→STAT6/others; clinical responses to JAK inhibition reflect pathway centrality (Jun 2025; URL below). (urzua2025skinbarrierdysfunction pages 3-4) - Systems endotypes: Cross-tissue transcriptomics reveal modules linked to erythema vs papulation and longitudinal clusters tied to severity and treatment response; proteomic modules correlate with disease activity (Oct 2023; URL below). (bilinski2025antiinflammatorytherapiesfor pages 2-4)

  • Dysregulated molecular pathways

  • IL-4/IL-13–STAT6 signaling; IL-31–neuronal TRP channels; alarmin (TSLP/IL-33/IL-25)–DC/ILC2 pathways; NF-κB and MAPK in keratinocytes; JAK–STAT (kamata2025mechanismsofitch pages 2-4, bai2025atopicdermatitisdiagnosis pages 25-26, torres2025interleukin4andatopic pages 14-15, urzua2025skinbarrierdysfunction pages 3-4)

  • Affected cellular processes

  • Keratinocyte differentiation and junctional assembly; sensory neuron excitability and neurite extension; DC antigen presentation; Th2/ILC2 cytokine production; pruritus transmission (katsarou2023theroleof pages 12-12, kamata2025mechanismsofitch pages 2-4, bai2025atopicdermatitisdiagnosis pages 25-26)

2) Key Molecular Players (ontology-ready annotations) - Genes/Proteins (HGNC symbol) - FLG (filaggrin): epidermal barrier scaffold; loss-of-function predisposes to AD (HGNC: 3752). (katsarou2023theroleof pages 12-12) - CLDN1 (claudin-1): tight junction component; reduced in AD lesions; Th2 cytokine–sensitive (HGNC: 2031). (katsarou2023theroleof pages 12-12) - IL4, IL13: type 2 cytokines central to AD pathogenesis (HGNC: 6014, 5991). (torres2025interleukin4andatopic pages 14-15) - IL31, IL31RA, OSMR: pruritogenic pathway receptors on sensory neurons (HGNC: 20497, 21491, 8506). (kamata2025mechanismsofitch pages 2-4, bai2025atopicdermatitisdiagnosis pages 25-26) - TSLP, IL33, IL25/IL17E: epithelial alarmins initiating type 2 responses (HGNC: 30742, 5996, 5964). (kamata2025mechanismsofitch pages 2-4, torres2025interleukin4andatopic pages 14-15) - JAK1, JAK2; STAT6: JAK–STAT transducers in type 2 signaling (HGNC: 6190, 6192, 11366). (urzua2025skinbarrierdysfunction pages 3-4, torres2025interleukin4andatopic pages 14-15) - CALCA (CGRP): neuropeptide mediating IL-31 neurogenic restraint (HGNC: 1434). (bai2025atopicdermatitisdiagnosis pages 25-26) - TRPV1, TRPA1: neuronal ion channels mediating itch (HGNC: 12306, 132). (kamata2025mechanismsofitch pages 2-4)

  • Chemical entities (CHEBI)
  • Ceramide (CHEBI:17761): altered chain-length composition in AD barrier lipid matrix (review synthesis). (urzua2025skinbarrierdysfunction pages 3-4)

  • Histamine (CHEBI:18295): mast-cell mediator contributing to pruritus (review synthesis). (torres2025interleukin4andatopic pages 14-15)

  • Cell types (CL terms)

  • Keratinocyte (CL:0000312); Langerhans cell (CL:0000475); Dendritic cell (CL:0000451); ILC2 (CL:0001065); Th2 cell (CL:0000910); Sensory neuron (CL:0000101). (kamata2025mechanismsofitch pages 2-4, katsarou2023theroleof pages 12-12, torres2025interleukin4andatopic pages 14-15)

  • Anatomical locations (UBERON)

  • Epidermis (UBERON:0001003); Dermis (UBERON:0002067); Skin nerve endings (UBERON:0001825). (kamata2025mechanismsofitch pages 2-4, katsarou2023theroleof pages 12-12)

  • Drugs/biologics (mechanism-linked)

  • Dupilumab (anti–IL-4Rα; blocks IL-4/IL-13 signaling). (torres2025interleukin4andatopic pages 14-15)
  • Tralokinumab, lebrikizumab (anti–IL-13). (torres2025interleukin4andatopic pages 14-15)
  • Oral/topical JAK inhibitors (e.g., upadacitinib, baricitinib; ruxolitinib cream). (urzua2025skinbarrierdysfunction pages 3-4)

3) Biological Processes (GO) disrupted - Keratinocyte differentiation (GO:0030216); Cornified envelope assembly (GO:0070268) (FLG-related). (katsarou2023theroleof pages 12-12) - Tight junction organization (GO:0034330) (CLDN1-related). (katsarou2023theroleof pages 12-12) - Cytokine-mediated signaling pathway (GO:0019221) via JAK–STAT (GO:0007259). (urzua2025skinbarrierdysfunction pages 3-4, torres2025interleukin4andatopic pages 14-15) - Immune response–Th2 cell differentiation (GO:0042092); ILC2 activation (GO:0001773). (torres2025interleukin4andatopic pages 14-15) - Sensory perception of itch (GO:0036231); Neuron projection development (GO:0031175) (IL-31–induced neurite extension). (kamata2025mechanismsofitch pages 2-4) - Neurogenic inflammation (GO:0050729) via CGRP signaling impacting T cells. (bai2025atopicdermatitisdiagnosis pages 25-26)

4) Cellular Components (GO-CC) - Cornified envelope (GO:0001533); Keratin filament (GO:0045095). (katsarou2023theroleof pages 12-12) - Tight junction (GO:0005923). (katsarou2023theroleof pages 12-12) - Plasma membrane of pruritoceptors (GO:0005886) housing TRPV1/TRPA1 and IL31RA/OSMR. (kamata2025mechanismsofitch pages 2-4) - Extracellular space (GO:0005615) for cytokines and neuropeptides (IL-4/IL-13/IL-31, CGRP). (torres2025interleukin4andatopic pages 14-15, bai2025atopicdermatitisdiagnosis pages 25-26)

5) Disease Progression (sequence of events) - Initiation: Genetic predisposition (e.g., FLG variants) and environmental insults disrupt the barrier and elevate skin pH; TJ/FLG insufficiency increases permeability. (katsarou2023theroleof pages 12-12) - Epithelial alarm: Keratinocytes release alarmins (TSLP, IL-33, IL-25), activating DCs/ILC2 and priming Th2 responses. (kamata2025mechanismsofitch pages 2-4, torres2025interleukin4andatopic pages 14-15) - Amplification: IL-4/IL-13 from Th2/ILC2 downregulate barrier genes (e.g., FLG, CLDN1), recruit inflammatory cells, and perpetuate itch–scratch cycles; JAK–STAT transduces these signals. (torres2025interleukin4andatopic pages 14-15, urzua2025skinbarrierdysfunction pages 3-4) - Pruritus circuitry: IL-31 directly activates IL31RA/OSMR+ TRPV1/TRPA1 neurons, enhances nerve fiber density, and drives chronic itch behavior. (kamata2025mechanismsofitch pages 2-4) - Chronic modulation: With repeated allergen exposure, IL-31–induced CGRP imposes a neurogenic restraint on tissue Th2 inflammation—an adaptive feedback that may be perturbed by anti-IL31RA therapies. (bai2025atopicdermatitisdiagnosis pages 25-26) - Endotypic divergence: Cross-tissue transcriptomic modules align with clinical phenotypes and severity clusters and can inform treatment monitoring/response. (bilinski2025antiinflammatorytherapiesfor pages 2-4)

6) Phenotypic Manifestations (clinical; HP terms) - Pruritus (HP:0000989) driven by IL-31–TRP pathways and hyperinnervation; quote above. (kamata2025mechanismsofitch pages 2-4) - Eczema/erythematous scaly dermatitis (HP:0000988) from Th2-driven skin inflammation and barrier leak. (torres2025interleukin4andatopic pages 14-15, katsarou2023theroleof pages 12-12) - Xerosis (HP:0000958) from barrier lipid/protein deficits. (katsarou2023theroleof pages 12-12) - Lichenification (HP:0000984) in chronic disease, aligned with distinct transcriptomic modules. (bilinski2025antiinflammatorytherapiesfor pages 2-4)

Recent developments and latest research (2023–2025; with URLs/dates) - IL-31 neuroimmune restraint of Th2 inflammation (Science Immunology, Oct 2023): Demonstrated that IL-31–responsive pruritoceptors release CGRP to limit cutaneous type 2 programs in chronic HDM dermatitis; mechanistic insight into paradoxical flares on anti-IL31RA therapy. URL: https://doi.org/10.1126/sciimmunol.abi6887. (bai2025atopicdermatitisdiagnosis pages 25-26) - Systems endotyping (Nature Communications, Oct 2023): Cross-tissue transcriptomics linked detailed skin phenotypes (erythema vs papulation) with distinct immune signatures and identified blood transcriptome clusters tracking severity and treatment history, enabling personalized monitoring. URL: https://doi.org/10.1038/s41467-023-41857-8. (bilinski2025antiinflammatorytherapiesfor pages 2-4) - Tight-junction barrier in AD (J Clin Med, Feb 2023): Systematic review highlighting claudin-1 reduction, Th2 suppression of claudins, and scratching-induced claudin-1 decreases as central to barrier pathophysiology. URL: https://doi.org/10.3390/jcm12041538. (katsarou2023theroleof pages 12-12) - Itch mechanisms synthesis (Juntendo Med J, Jan 2025): Integrated view of Th2/alarmin–neuronal crosstalk, IL-31 receptor expression on pruritoceptors, and hyperinnervation mechanisms (Sema3A↓, NGF↑). URL: https://doi.org/10.14789/ejmj.jmj24-0036-r. (kamata2025mechanismsofitch pages 2-4) - IL-4 centrality and therapeutic implications (Dermatology and Therapy, Feb 2025): Review underscoring IL-4/IL-13 as nexus for barrier, dysbiosis, itch, and inflammation; contextualizes dupilumab and IL-13 inhibitors. URL: https://doi.org/10.1007/s13555-025-01352-y. (torres2025interleukin4andatopic pages 14-15) - Barrier, immunity, and targeted therapy integration (Cureus, Jun 2025): Review summarizing evidence for IL-13 blockade improving barrier function and rapid efficacy of JAK inhibitors; notes emerging microbiome-directed approaches. URL: https://doi.org/10.7759/cureus.86937. (urzua2025skinbarrierdysfunction pages 3-4)

Current applications and real-world implementations - IL-4/IL-13 pathway blockade - Dupilumab (anti–IL-4Rα) is a standard of care for moderate–severe AD; reviews document early and sustained improvements in systemic and cutaneous immune abnormalities, consistent with interruption of the type 2 axis (reviewed 2025; URL above). (torres2025interleukin4andatopic pages 14-15) - IL-13–selective monoclonals (tralokinumab, lebrikizumab) have demonstrated efficacy in phase III trials and are integrated in recent therapeutic reviews (2025 summary; mechanism detailed in 2025 narrative review). (torres2025interleukin4andatopic pages 14-15) - JAK inhibitors - Oral JAK1-selective agents (e.g., upadacitinib) and JAK1/2 (baricitinib) and topical ruxolitinib cream show rapid pruritus and lesion improvement consistent with broad cytokine signal interruption (2025 review synthesis). (urzua2025skinbarrierdysfunction pages 3-4) - Monitoring and personalization - Multi-omic endotyping and cross-tissue modules are being developed for patient stratification and longitudinal monitoring, aligning skin phenotypes and blood modules with severity and response (Oct 2023). (bilinski2025antiinflammatorytherapiesfor pages 2-4)

Expert opinions and analysis - “IL-4 plays a critical role in skin barrier dysfunction, dysbiosis, pruritus, and inflammation” (Dermatology and Therapy, Feb 2025), anchoring IL-4/IL-13 as prime nodes for disease modification. URL: https://doi.org/10.1007/s13555-025-01352-y. (torres2025interleukin4andatopic pages 14-15) - “Impaired TJ barrier function and skin permeability in AD lesions is correlated with cldn-1 levels. Th2 inflammation inhibits the expression of cldn-1 and cldn-23… Scratching has also been reported to decrease cldn-1” (J Clin Med, Feb 2023), highlighting actionable barrier–immune feedbacks. URL: https://doi.org/10.3390/jcm12041538. (katsarou2023theroleof pages 12-12) - “IL-31 directly induces pruritus… and selectively promotes nerve fiber extension” (Juntendo Med J, Jan 2025), connecting cytokine signaling to neuronal remodeling. URL: https://doi.org/10.14789/ejmj.jmj24-0036-r. (kamata2025mechanismsofitch pages 2-4) - “IL-31… restrains cutaneous type 2 inflammation… [via] CGRP” (Science Immunology, Oct 2023), reframing IL-31 as both pruritogen and neuroimmune modulator. URL: https://doi.org/10.1126/sciimmunol.abi6887. (bai2025atopicdermatitisdiagnosis pages 25-26)

Relevant statistics and data from recent studies - Endotypic clustering: Integrated analysis of 115 AD patients and 14 controls identified skin–blood modules linking specific clinical features (erythema vs papulation) and longitudinal blood clusters aligned with severity and treatment history (Nature Communications, Oct 2023; details in article). URL: https://doi.org/10.1038/s41467-023-41857-8. (bilinski2025antiinflammatorytherapiesfor pages 2-4) - Barrier correlates: Systematic review collating >50 studies concluded that decreased claudin-1 associates with increased permeability and susceptibility to infection/allergen penetration; Th2 cytokines reduce claudin expression; scratching lowers claudin-1 (Feb 2023). URL: https://doi.org/10.3390/jcm12041538. (katsarou2023theroleof pages 12-12) - Neuroimmune plasticity: Clinical-pathobiological observations summarized in 2025 review include reduced Sema3A and increased NGF correlating with increased intraepidermal nerve density across AD states (Jan 2025). URL: https://doi.org/10.14789/ejmj.jmj24-0036-r. (kamata2025mechanismsofitch pages 2-4)

Evidence items (with PMIDs/DOIs/URLs) - Fassett MS et al. IL-31–dependent neurogenic inflammation restrains cutaneous type 2 immune response in allergic dermatitis. Science Immunology. Oct 2023. DOI: 10.1126/sciimmunol.abi6887; URL: https://doi.org/10.1126/sciimmunol.abi6887. Key quote and mechanism above. (bai2025atopicdermatitisdiagnosis pages 25-26) - Kamata Y et al. Mechanisms of Itch in Atopic Dermatitis. Juntendo Medical Journal. Jan 2025. DOI: 10.14789/ejmj.jmj24-0036-r; URL: https://doi.org/10.14789/ejmj.jmj24-0036-r. Key quote on IL-31 neurite extension; neuronal receptor expression. (kamata2025mechanismsofitch pages 2-4) - Katsarou S et al. The Role of Tight Junctions in Atopic Dermatitis: A Systematic Review. J Clin Med. Feb 2023. DOI: 10.3390/jcm12041538; URL: https://doi.org/10.3390/jcm12041538. Key quote on claudins/Th2 inhibition. (katsarou2023theroleof pages 12-12) - Torres T et al. Interleukin-4 and Atopic Dermatitis. Dermatology and Therapy. Feb 2025. DOI: 10.1007/s13555-025-01352-y; URL: https://doi.org/10.1007/s13555-025-01352-y. Expert synthesis of IL-4/IL-13 centrality. (torres2025interleukin4andatopic pages 14-15) - Urzua IE et al. Skin Barrier Dysfunction… Cureus. Jun 2025. DOI: 10.7759/cureus.86937; URL: https://doi.org/10.7759/cureus.86937. Clinical integration of IL-13 blockade/barrier and JAK inhibitor kinetics. (urzua2025skinbarrierdysfunction pages 3-4) - Sekita A et al. Multifaceted analysis of cross-tissue transcriptomes… Nat Commun. Oct 2023. DOI: 10.1038/s41467-023-41857-8; URL: https://doi.org/10.1038/s41467-023-41857-8. Endotype–phenotype modules and longitudinal clusters. (bilinski2025antiinflammatorytherapiesfor pages 2-4)

Structured ontology annotations - Genes/Proteins (HGNC): FLG; CLDN1; IL4; IL13; IL31; IL31RA; OSMR; TSLP; IL33; JAK1; JAK2; STAT6; CALCA; TRPV1; TRPA1. (katsarou2023theroleof pages 12-12, kamata2025mechanismsofitch pages 2-4, bai2025atopicdermatitisdiagnosis pages 25-26, torres2025interleukin4andatopic pages 14-15, urzua2025skinbarrierdysfunction pages 3-4) - GO Biological Processes: keratinocyte differentiation; tight junction organization; cytokine-mediated signaling; JAK–STAT cascade; Th2 differentiation; sensory perception of itch; neurogenic inflammation. (katsarou2023theroleof pages 12-12, kamata2025mechanismsofitch pages 2-4, urzua2025skinbarrierdysfunction pages 3-4) - GO Cellular Components: tight junction; cornified envelope; plasma membrane; extracellular region. (katsarou2023theroleof pages 12-12, kamata2025mechanismsofitch pages 2-4) - Cell Types (CL): keratinocytes; Langerhans cells; dermal dendritic cells; ILC2; Th2 cells; small-diameter sensory neurons. (kamata2025mechanismsofitch pages 2-4, katsarou2023theroleof pages 12-12, torres2025interleukin4andatopic pages 14-15) - Anatomical Sites (UBERON): epidermis; dermis; cutaneous nerve endings. (kamata2025mechanismsofitch pages 2-4, katsarou2023theroleof pages 12-12) - Chemical entities (CHEBI): ceramide (CHEBI:17761); histamine (CHEBI:18295). (urzua2025skinbarrierdysfunction pages 3-4, torres2025interleukin4andatopic pages 14-15) - Phenotypes (HPO): pruritus (HP:0000989); eczema (HP:0000988); xerosis (HP:0000958); lichenification (HP:0000984). (kamata2025mechanismsofitch pages 2-4, katsarou2023theroleof pages 12-12, bilinski2025antiinflammatorytherapiesfor pages 2-4)

Therapeutic implications (mechanism → therapy mapping) - IL-4/IL-13 axis: Dupilumab (anti–IL-4Rα), tralokinumab/lebrikizumab (anti–IL-13) reduce type 2 signaling, improve lesions and often pruritus; reviews emphasize their disease-modifying potential by interrupting central drivers (2025). (torres2025interleukin4andatopic pages 14-15) - IL-31 axis: Anti–IL-31/IL31RA agents target pruritus; the 2023 mechanistic study suggests monitoring for inflammatory shifts due to loss of IL-31–CGRP restraint in chronic exposure contexts (Oct 2023). (bai2025atopicdermatitisdiagnosis pages 25-26) - JAK inhibitors: Oral JAK1/2 and topical JAK inhibitors rapidly reduce itch and inflammation—a pharmacodynamic signature of blocking multi-cytokine signaling via JAK–STAT (2025). (urzua2025skinbarrierdysfunction pages 3-4) - Barrier-directed adjuncts: Because Th2 cytokines downregulate CLDN1/FLG, upstream cytokine blockade plus barrier repair strategies target both cause and consequence (2023–2025 syntheses). (katsarou2023theroleof pages 12-12, torres2025interleukin4andatopic pages 14-15)

Limitations and gaps - While reviews integrate barrier, IL-4/IL-13, IL-31, and JAK–STAT mechanisms with therapeutic success, high-resolution causal links for all epithelial alarmins in human endotypes and long-term remodeling remain under active investigation. Multi-omic signatures are promising but require prospective validation for treatment selection in routine care. (bilinski2025antiinflammatorytherapiesfor pages 2-4)

References with URLs/dates - Science Immunology, Oct 2023: https://doi.org/10.1126/sciimmunol.abi6887. (bai2025atopicdermatitisdiagnosis pages 25-26) - Nature Communications, Oct 2023: https://doi.org/10.1038/s41467-023-41857-8. (bilinski2025antiinflammatorytherapiesfor pages 2-4) - Journal of Clinical Medicine, Feb 2023: https://doi.org/10.3390/jcm12041538. (katsarou2023theroleof pages 12-12) - Juntendo Medical Journal, Jan 2025: https://doi.org/10.14789/ejmj.jmj24-0036-r. (kamata2025mechanismsofitch pages 2-4) - Dermatology and Therapy, Feb 2025: https://doi.org/10.1007/s13555-025-01352-y. (torres2025interleukin4andatopic pages 14-15) - Cureus, Jun 2025: https://doi.org/10.7759/cureus.86937. (urzua2025skinbarrierdysfunction pages 3-4)

References

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