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Pars Planitis

Complex MONDO:0011644 Inflammatory Disorder Ophthalmic Disorder
0
Mappings
0
Definitions
0
Inheritance
5
Pathophysiology
0
Histopathology
7
Phenotypes
2
Genes
4
Treatments
2
Subtypes
6
Differentials
0
Datasets
0
Trials
◆

Subtypes

2
Idiopathic Pars Planitis
Chronic intermediate uveitis with no identifiable underlying systemic disease or infection.
Show evidence (1 reference)
PMID:39360991 SUPPORT
"Pars planitis is the term used for idiopathic intermediate uveitis that presents with snowballs and snowbanks."
This represents the classic form of pars planitis where no underlying cause can be identified.
Secondary Pars Planitis
Intermediate uveitis with similar features but associated with systemic conditions like multiple sclerosis or sarcoidosis.
Show evidence (1 reference)
PMID:39360991 SUPPORT
"Etiology can be infectious, associated with a systemic disease, neoplastic or idiopathic."
Secondary pars planitis occurs when intermediate uveitis is linked to an underlying systemic or infectious condition.
⚙

Pathophysiology

5
Autoimmune T-Cell Predominant Inflammation
Pars planitis shows a T cell-driven autoimmune response within the vitreous and pars plana.
T cell link
Adaptive immune response link
Vitreous humor link Pars plana link
Show evidence (2 references)
PMID:26438050 SUPPORT
"Clinical and histopathological findings suggest an autoimmune etiology, most likely as a reaction to endogenous antigen of unknown source, with T cells predominant in both vitreous and pars plana infiltrations."
Shows T-cell predominance in ocular infiltrates supporting autoimmune pathogenesis.
PMID:37976519 SUPPORT
"It is thought to be a T-cell mediated disease with a genetic predisposition."
Confirms T-cell mediated immunopathogenesis and genetic susceptibility in pars planitis.
Vitreous Cell Infiltration
Dense inflammatory cell infiltration and haze within the vitreous cavity.
T cell link
Inflammatory response link
Vitreous humor link
Show evidence (2 references)
PMID:27051493 SUPPORT
"Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis."
Documents vitreous cell infiltration and haze as defining inflammatory findings.
PMID:28389773 SUPPORT
"Vitreous inflammation (100%), vitreous haze (92.6%), snowballs (74.1%), snowbanks (66.7%)...were the most common presentations."
Confirms high prevalence of vitreous inflammation and snowballs in clinical cohorts.
Snowbank Formation at Pars Plana
Exudative and fibrocellular snowbank deposition along the pars plana and vitreous base.
Astrocyte link
Extracellular matrix organization link
Pars plana link Peripheral retina link
Show evidence (1 reference)
PMID:28389773 SUPPORT
"Vitreous inflammation (100%), vitreous haze (92.6%), snowballs (74.1%), snowbanks (66.7%)...were the most common presentations."
Shows snowbanks as a frequent structural manifestation of pars planitis at the pars plana.
Peripheral Retinal Vasculitis and Sheathing
Inflammation of peripheral retinal vessels leading to vascular sheathing and leakage.
Endothelial cell of vascular tree link
Inflammatory response link
Peripheral retina link
Show evidence (2 references)
PMID:27051493 SUPPORT
"Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings."
Notes peripheral retinal vasculitis as a recognized manifestation in pars planitis.
PMID:28389773 SUPPORT
"...peripheral retinal vascular sheathing (48.1%) were the most common presentations."
Confirms high frequency of peripheral vascular sheathing in clinical series.
Macular Thickening from Blood-Retinal Barrier Breakdown
Inflammatory vascular leakage causes subclinical or clinical macular thickening that can progress to cystoid macular edema.
Endothelial cell of vascular tree link
Regulation of vascular permeability link
Macula of retina link
Show evidence (2 references)
PMID:27188332 SUPPORT
"The cut-off value of CFT for initiating systemic treatment was determined at 215.5 μm in a post hoc analysis (sensitivity 62.5 %, specificity 96.4 %)."
Shows that macular thickening beyond a threshold prompts treatment due to risk of vision loss in intermediate uveitis.
PMID:33559832 SUPPORT
"According to multivariate linear regression analysis, the presence of DME, and loss of normal foveal contour appearance at baseline were the independent factors associated with BCVA at the final examination."
OCT-defined diffuse macular edema and foveal contour loss predict worse visual acuity, underscoring the impact of macular thickening.
⬡

Causal Graph

graph LR
    Peripheral_Retinal_Vasculitis_and_Sheathing["Peripheral Retinal Vasculitis and Sheathing"]
    Vitreous_Cell_Infiltration["Vitreous Cell Infiltration"]
    Macular_Edema["Macular Edema"]
    Visual_Impairment["Visual Impairment"]
    Macular_Thickening_from_Blood_Retinal_Barrier_Breakdown["Macular Thickening from Blood-Retinal Barrier Breakdown"]

    Vitreous_Cell_Infiltration --> Visual_Impairment
    Peripheral_Retinal_Vasculitis_and_Sheathing --> Macular_Edema
    Macular_Thickening_from_Blood_Retinal_Barrier_Breakdown --> Visual_Impairment

    style Peripheral_Retinal_Vasculitis_and_Sheathing fill:#dbeafe
    style Vitreous_Cell_Infiltration fill:#dbeafe
    style Macular_Edema fill:#fef3c7
    style Visual_Impairment fill:#fef3c7
    style Macular_Thickening_from_Blood_Retinal_Barrier_Breakdown fill:#dbeafe
●

Phenotypes

7
Blurred Vision VERY_FREQUENT Sensory HP:0000622
Show evidence (1 reference)
PMID:27051493 SUPPORT
"The most common presenting symptoms are floaters and blurred vision."
Blurred vision is a core presenting symptom reported in pars planitis.
Floaters VERY_FREQUENT Sensory HP:0100832
Dark spots or strings that appear to float in the visual field
Show evidence (1 reference)
PMID:27051493 SUPPORT
"The most common presenting symptoms are floaters and blurred vision."
Floaters are among the predominant presenting symptoms of pars planitis.
Visual Impairment FREQUENT Sensory HP:0000505
May progress to severe vision loss if untreated
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Although pars planitis is known to be a benign form of uveitis in most cases, it may become a potentially blinding disease due to complications including cataract, cystoid macular edema, vitreous opacities and optic disc edema."
Chronic inflammation can lead to complications that threaten vision if not controlled.
Vitreous Opacities FREQUENT Ocular HP:0004327
Inflammatory debris and cells in the vitreous chamber
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis."
Vitreous opacities such as snowballs are typical inflammatory findings in pars planitis.
Macular Edema OCCASIONAL Ocular HP:0040049
Cystoid macular edema is the most common cause of visual morbidity
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Cystoid macular edema is the most common cause of visual morbidity."
Macular edema represents a significant complication that can lead to permanent vision loss.
Optic Disc Swelling OCCASIONAL Ocular HP:0001085
Inflammatory involvement of the optic nerve
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings."
Optic disc edema is a recognized complication of pars planitis.
Retinal Pigmentation Abnormality (Bone Spicules) RARE Ocular HP:0007703
Inflammatory pseudo-retinitis pigmentosa pattern following pars planitis episodes
Show evidence (1 reference)
PMID:30200907 SUPPORT
"Progressive, intraretinal bone crepuscule pigmentation developed in his left retina during the following three months."
Describes bone spicule-like pigmentation emerging after bilateral pars planitis, mimicking retinitis pigmentosa.
🧬

Genetic Associations

2
HLA-DR15 (Risk Factor)
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Associations between pars planitis and HLA-DR2, -DR15, -B51 and -DRB1*0802 haplotypes have been described suggesting an immunogenetic predisposition."
HLA-DR15 has been linked to immunogenetic susceptibility in pars planitis.
HLA-B51 (Risk Factor)
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Associations between pars planitis and HLA-DR2, -DR15, -B51 and -DRB1*0802 haplotypes have been described suggesting an immunogenetic predisposition."
HLA-B51 is reported among haplotypes associated with pars planitis, supporting a genetic component.
💊

Treatments

4
Corticosteroids MAXO:0000058
First-line treatment for reducing inflammation in pars planitis.
Show evidence (1 reference)
PMID:27051493 SUPPORT
"A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis."
Corticosteroids form the foundation of treatment for pars planitis.
Immunosuppressive Agents MAXO:0000058
Second-line therapy for chronic or steroid-resistant cases.
Show evidence (1 reference)
PMID:27051493 SUPPORT
"Methotrexate is the most widely used first-line immunosuppressive agent in children with chronic non-infectious uveitis because of its long-term safety record and well tolerance."
Immunosuppressive agents, particularly methotrexate, provide steroid-sparing control for chronic cases.
Biological Therapy MAXO:0000058
TNF-alpha inhibitors for refractory cases.
Show evidence (1 reference)
PMID:34568953 SUPPORT
"ADA was initiated in 23 patients (38.9%) due to refractory uveitis and adverse effects to the corticosteroid and helped control intraocular inflammation and decrease the use of systemic steroids/immunosuppressives in 22 of 23 (95%) of patients who received ADA."
TNF-alpha inhibition with adalimumab controlled inflammation and enabled steroid-sparing in refractory cases.
Pars Plana Vitrectomy MAXO:0000004
Surgical intervention for severe vitreous opacities or complications.
Show evidence (1 reference)
PMID:27051493 SUPPORT
"A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis."
Surgical intervention may be necessary for cases with severe vitreous involvement or complications.
🌍

Environmental Factors

2
Arboviral Infection (Chikungunya)
Arboviral infections such as chikungunya can present as intermediate uveitis and should be excluded before labeling idiopathic pars planitis.
Show evidence (1 reference)
PMID:28010143 SUPPORT
"Exam revealed a unilateral intermediate uveitis, with an extensive work-up positive for chikungunya virus immunoglobulin M and G titers."
Demonstrates that chikungunya infection can manifest as intermediate uveitis, making viral screening important in suspected pars planitis.
Systemic Infection Exclusion
By definition pars planitis lacks an associated systemic infection; suspected cases warrant workup to rule out infectious causes before confirming idiopathic disease.
Show evidence (1 reference)
PMID:28613790 SUPPORT
"Pars planitis is chronic intermediate uveitis for which no systemic disease or associated infection could be found."
Clarifies that absence of systemic infection is required to diagnose idiopathic pars planitis, guiding environmental trigger evaluation.
🔀

Differential Diagnoses

6

Conditions with similar clinical presentations that must be differentiated from Pars Planitis:

Birdshot Retinochoroiditis Not Yet Curated MONDO:0011599
Overlapping Features Retinal vasculitis with HLA-A29 positivity can mimic intermediate uveitis but has a distinct angiographic signature.
Distinguishing Features
  • Scoring of retinal vasculitis features such as disc hyperfluorescence and profuse posterior leakage separates birdshot retinochoroiditis from pars planitis.
  • Confirmation of HLA-A29 antigen supports birdshot retinochoroiditis, whereas pars planitis has no HLA antigen requirement.
Show evidence (2 references)
PMID:40642353 SUPPORT
"HLA-A29 antigen was present in all patients (100%)."
Confirms the defining HLA-A29 positivity used to differentiate birdshot retinochoroiditis from pars planitis in comparative cohorts.
PMID:40642353 SUPPORT
"Retinal vasculitis related to BRC has specific findings leading, if present, to the diagnosis of BRC that should be ascertained by the search of indocyanine green angiography lesions with the ultimate confirmation by the presence of the HLA-A29 antigen."
Specific vasculitis features plus HLA-A29 confirmation distinguish birdshot retinochoroiditis from pars planitis.
Retinoblastoma (Masquerade Syndrome) MONDO:0008380
Overlapping Features Retinoblastoma can present with vitreous seeding and mimic inflammatory vitreous snowballs seen in pars planitis.
Distinguishing Features
  • Presence of an intraocular mass with diffuse vitreous seeding rather than inflammatory snowballs.
  • Regression with intra-arterial or intravitreal chemotherapy instead of corticosteroid or immunosuppressive therapy.
Show evidence (1 reference)
PMID:41334298 SUPPORT
"Fundus examination with indirect ophthalmoscopy at our center revealed a fundus mass with diffuse vitreous seeding."
Demonstrates that a fundus mass with vitreous seeding signals retinoblastoma rather than inflammatory pars planitis.
Infectious Masquerade Intermediate Uveitis
Overlapping Features Infectious entities can mimic intermediate uveitis presentations and must be excluded before diagnosing idiopathic pars planitis.
Distinguishing Features
  • PCR testing and directed serologies identify infectious causes rather than idiopathic inflammation.
  • Targeted antimicrobial therapy improves infectious masquerade syndromes, unlike corticosteroid-responsive pars planitis.
Show evidence (1 reference)
PMID:39360991 SUPPORT
"PCR testing has enhanced the ability to diagnose infectious and neoplastic conditions that masquerade as intermediate uveitis."
Shows that molecular testing uncovers infectious causes that can mimic pars planitis.
Intraocular Lymphoma (Masquerade Syndrome) Not Yet Curated MONDO:0004351
Overlapping Features Primary intraocular lymphoma can imitate intermediate uveitis with vitreous cells and requires oncologic evaluation.
Distinguishing Features
  • Presence of malignant lymphoid cells in ocular fluid or tissue differentiates lymphoma from idiopathic inflammation.
  • Responds to oncologic therapy rather than corticosteroids alone.
Show evidence (1 reference)
PMID:39360991 SUPPORT
"Etiology can be infectious, associated with a systemic disease, neoplastic or idiopathic."
Notes that neoplastic causes such as intraocular lymphoma can masquerade as intermediate uveitis and must be excluded.
Multiple Sclerosis-Associated Intermediate Uveitis MONDO:0005301
Overlapping Features Intermediate uveitis secondary to multiple sclerosis can resemble pars planitis but carries neurologic signs and demyelinating lesions.
Distinguishing Features
  • Neurologic symptoms and MRI-demonstrated demyelinating lesions support multiple sclerosis-associated uveitis rather than idiopathic pars planitis.
  • Workup for demyelinating disease is required when intermediate uveitis co-occurs with neurologic complaints.
Show evidence (1 reference)
PMID:33845006 SUPPORT
"Key exclusions included: 1) multiple sclerosis, 2) sarcoidosis, and 3) syphilis."
The SUN criteria treat multiple sclerosis as an exclusion, underscoring the need to differentiate it from idiopathic pars planitis.
Sarcoidosis-Associated Intermediate Uveitis with Vasoproliferative Tumor MONDO:0019338
Overlapping Features Sarcoidosis-related intermediate uveitis can produce peripheral vasoproliferative tumors and exudative detachment, mimicking complicated pars planitis.
Distinguishing Features
  • Systemic sarcoidosis history with granulomatous uveitis plus a peripheral retinal vascular mass points to sarcoid-associated intermediate uveitis rather than idiopathic pars planitis.
  • Exudative retinal detachment arising from a vasoproliferative tumor that regresses with combined steroid-sparing immunosuppression, vitrectomy, and tumor-directed cryotherapy distinguishes this entity.
Show evidence (1 reference)
PMID:38645965 SUPPORT
"She had active vitritis, and a peripheral retinal vascular mass was noted in the superotemporal periphery. The mass was associated with ERD involving the posterior pole."
Highlights sarcoidosis-associated intermediate uveitis complicated by vasoproliferative tumor and exudative detachment, requiring differentiation from idiopathic pars planitis.
{ }

Source YAML

click to show 
name: Pars Planitis
creation_date: '2026-01-08T01:24:35Z'
updated_date: '2026-01-21T21:12:35Z'
category: Complex
parents:
- Inflammatory Disorder
- Ophthalmic Disorder
has_subtypes:
- name: Idiopathic Pars Planitis
  description: Chronic intermediate uveitis with no identifiable underlying systemic disease or infection.
  evidence:
  - reference: PMID:39360991
    supports: SUPPORT
    snippet: "Pars planitis is the term used for idiopathic intermediate uveitis that presents with snowballs and snowbanks."
    explanation: This represents the classic form of pars planitis where no underlying cause can be identified.
- name: Secondary Pars Planitis
  description: Intermediate uveitis with similar features but associated with systemic conditions like multiple sclerosis or sarcoidosis.
  evidence:
  - reference: PMID:39360991
    supports: SUPPORT
    snippet: "Etiology can be infectious, associated with a systemic disease, neoplastic or idiopathic."
    explanation: Secondary pars planitis occurs when intermediate uveitis is linked to an underlying systemic or infectious condition.
pathophysiology:
- name: Autoimmune T-Cell Predominant Inflammation
  description: Pars planitis shows a T cell-driven autoimmune response within the vitreous and pars plana.
  cell_types:
  - preferred_term: T cell
    term:
      id: CL:0000084
      label: T cell
  biological_processes:
  - preferred_term: Adaptive immune response
    term:
      id: GO:0002250
      label: adaptive immune response
  locations:
  - preferred_term: Vitreous humor
    term:
      id: UBERON:0001286
      label: vitreous humor
  - preferred_term: Pars plana
    term:
      id: UBERON:0004548
      label: pars plana of ciliary body
  evidence:
  - reference: PMID:26438050
    supports: SUPPORT
    snippet: "Clinical and histopathological findings suggest an autoimmune etiology, most likely as a reaction to endogenous antigen of unknown source, with T cells predominant in both vitreous and pars plana infiltrations."
    explanation: Shows T-cell predominance in ocular infiltrates supporting autoimmune pathogenesis.
  - reference: PMID:37976519
    supports: SUPPORT
    snippet: "It is thought to be a T-cell mediated disease with a genetic predisposition."
    explanation: Confirms T-cell mediated immunopathogenesis and genetic susceptibility in pars planitis.
- name: Vitreous Cell Infiltration
  description: Dense inflammatory cell infiltration and haze within the vitreous cavity.
  cell_types:
  - preferred_term: T cell
    term:
      id: CL:0000084
      label: T cell
  downstream:
  - target: Visual Impairment
    description: Vitreous cells and haze obscure the visual axis causing floaters and blurred vision.
    evidence:
    - reference: PMID:27051493
      supports: SUPPORT
      snippet: "The most common presenting symptoms are floaters and blurred vision."
      explanation: Early visual symptoms arise from inflammatory cells and haze in the vitreous cavity.
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  locations:
  - preferred_term: Vitreous humor
    term:
      id: UBERON:0001286
      label: vitreous humor
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis."
    explanation: Documents vitreous cell infiltration and haze as defining inflammatory findings.
  - reference: PMID:28389773
    supports: SUPPORT
    snippet: "Vitreous inflammation (100%), vitreous haze (92.6%), snowballs (74.1%), snowbanks (66.7%)...were the most common presentations."
    explanation: Confirms high prevalence of vitreous inflammation and snowballs in clinical cohorts.
- name: Snowbank Formation at Pars Plana
  description: Exudative and fibrocellular snowbank deposition along the pars plana and vitreous base.
  cell_types:
  - preferred_term: Astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: Extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
  locations:
  - preferred_term: Pars plana
    term:
      id: UBERON:0004548
      label: pars plana of ciliary body
  - preferred_term: Peripheral retina
    term:
      id: UBERON:0001789
      label: retina
  evidence:
  - reference: PMID:28389773
    supports: SUPPORT
    snippet: "Vitreous inflammation (100%), vitreous haze (92.6%), snowballs (74.1%), snowbanks (66.7%)...were the most common presentations."
    explanation: Shows snowbanks as a frequent structural manifestation of pars planitis at the pars plana.
- name: Peripheral Retinal Vasculitis and Sheathing
  description: Inflammation of peripheral retinal vessels leading to vascular sheathing and leakage.
  cell_types:
  - preferred_term: Endothelial cell of vascular tree
    term:
      id: CL:0002139
      label: endothelial cell of vascular tree
  downstream:
  - target: Macular Edema
    description: Peripheral vasculitis and leakage contribute to macular thickening that impairs vision.
    evidence:
    - reference: PMID:27188332
      supports: SUPPORT
      snippet: "Correlation between LogMAR visual acuity and central retinal thickness at baseline was strong (r = 0.7436, p < 0.0001)."
      explanation: Demonstrates that increased retinal thickness from leakage correlates with worse visual acuity in intermediate uveitis.
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  locations:
  - preferred_term: Peripheral retina
    term:
      id: UBERON:0001789
      label: retina
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings."
    explanation: Notes peripheral retinal vasculitis as a recognized manifestation in pars planitis.
  - reference: PMID:28389773
    supports: SUPPORT
    snippet: "...peripheral retinal vascular sheathing (48.1%) were the most common presentations."
    explanation: Confirms high frequency of peripheral vascular sheathing in clinical series.
- name: Macular Thickening from Blood-Retinal Barrier Breakdown
  description: Inflammatory vascular leakage causes subclinical or clinical macular thickening that can progress to cystoid macular edema.
  cell_types:
  - preferred_term: Endothelial cell of vascular tree
    term:
      id: CL:0002139
      label: endothelial cell of vascular tree
  downstream:
  - target: Visual Impairment
    description: Macular thickening degrades visual acuity in intermediate uveitis.
    evidence:
    - reference: PMID:27188332
      supports: SUPPORT
      snippet: "Correlation between LogMAR visual acuity and central retinal thickness at baseline was strong (r = 0.7436, p < 0.0001)."
      explanation: Links macular thickening to loss of visual acuity.
  biological_processes:
  - preferred_term: Regulation of vascular permeability
    term:
      id: GO:0043112
      label: regulation of vascular permeability
  locations:
  - preferred_term: Macula of retina
    term:
      id: UBERON:0008901
      label: macula lutea
  evidence:
  - reference: PMID:27188332
    supports: SUPPORT
    snippet: "The cut-off value of CFT for initiating systemic treatment was determined at 215.5 μm in a post hoc analysis (sensitivity 62.5 %, specificity 96.4 %)."
    explanation: Shows that macular thickening beyond a threshold prompts treatment due to risk of vision loss in intermediate uveitis.
  - reference: PMID:33559832
    supports: SUPPORT
    snippet: "According to multivariate linear regression analysis, the presence of DME, and loss of normal foveal contour appearance at baseline were the independent factors associated with BCVA at the final examination."
    explanation: OCT-defined diffuse macular edema and foveal contour loss predict worse visual acuity, underscoring the impact of macular thickening.
phenotypes:
- category: Sensory
  name: Blurred Vision
  frequency: VERY_FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "The most common presenting symptoms are floaters and blurred vision."
    explanation: Blurred vision is a core presenting symptom reported in pars planitis.
  phenotype_term:
    preferred_term: Blurred vision
    term:
      id: HP:0000622
      label: Blurred vision
- category: Sensory
  name: Floaters
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Dark spots or strings that appear to float in the visual field
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "The most common presenting symptoms are floaters and blurred vision."
    explanation: Floaters are among the predominant presenting symptoms of pars planitis.
  phenotype_term:
    preferred_term: Vitreous floaters
    term:
      id: HP:0100832
      label: Vitreous floaters
- category: Sensory
  name: Visual Impairment
  frequency: FREQUENT
  notes: May progress to severe vision loss if untreated
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Although pars planitis is known to be a benign form of uveitis in most cases, it may become a potentially blinding disease due to complications including cataract, cystoid macular edema, vitreous opacities and optic disc edema."
    explanation: Chronic inflammation can lead to complications that threaten vision if not controlled.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
- category: Ocular
  name: Vitreous Opacities
  frequency: FREQUENT
  notes: Inflammatory debris and cells in the vitreous chamber
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis."
    explanation: Vitreous opacities such as snowballs are typical inflammatory findings in pars planitis.
  phenotype_term:
    preferred_term: Abnormal vitreous humor morphology
    term:
      id: HP:0004327
      label: Abnormal vitreous humor morphology
- category: Ocular
  name: Macular Edema
  frequency: OCCASIONAL
  notes: Cystoid macular edema is the most common cause of visual morbidity
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Cystoid macular edema is the most common cause of visual morbidity."
    explanation: Macular edema represents a significant complication that can lead to permanent vision loss.
  phenotype_term:
    preferred_term: Macular edema
    term:
      id: HP:0040049
      label: Macular edema
- category: Ocular
  name: Optic Disc Swelling
  frequency: OCCASIONAL
  notes: Inflammatory involvement of the optic nerve
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings."
    explanation: Optic disc edema is a recognized complication of pars planitis.
  phenotype_term:
    preferred_term: Optic disc edema
    term:
      id: HP:0001085
      label: Papilledema
- category: Ocular
  name: Retinal Pigmentation Abnormality (Bone Spicules)
  frequency: RARE
  notes: Inflammatory pseudo-retinitis pigmentosa pattern following pars planitis episodes
  evidence:
  - reference: PMID:30200907
    supports: SUPPORT
    snippet: "Progressive, intraretinal bone crepuscule pigmentation developed in his left retina during the following three months."
    explanation: Describes bone spicule-like pigmentation emerging after bilateral pars planitis, mimicking retinitis pigmentosa.
  phenotype_term:
    preferred_term: Abnormality of retinal pigmentation
    term:
      id: HP:0007703
      label: Abnormality of retinal pigmentation
diagnosis:
- name: Dilated Fundus Examination
  presence: Positive
  notes: Reveals characteristic snowballs and snowbanks
  evidence:
  - reference: PMID:39360991
    supports: SUPPORT
    snippet: "Awareness of the presentation and a dilated fundus examination in patients presenting with floaters is essential to the diagnosis."
    explanation: Dilated fundus examination is essential for diagnosing intermediate uveitis and identifying the characteristic features of pars planitis.
- name: Optical Coherence Tomography (OCT)
  presence: Positive
  notes: Detects macular edema and monitors treatment response
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Cystoid macular edema is the most common cause of visual morbidity."
    explanation: OCT is the gold standard for detecting and monitoring cystoid macular edema, the most important complication of pars planitis.
  - reference: PMID:33559832
    supports: SUPPORT
    snippet: "The presence of DME, and loss of normal foveal contour appearance at baseline were the independent factors associated with BCVA at the final examination."
    explanation: OCT findings such as diffuse macular edema and foveal contour loss stratify visual risk and guide treatment intensity.
- name: Fluorescein Angiography
  presence: Positive
  notes: May show peripheral retinal vasculitis and capillary non-perfusion
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings."
    explanation: Fluorescein angiography is useful for documenting peripheral retinal vasculitis, a common finding in pars planitis.
- name: SUN Classification Criteria
  presence: Positive
  notes: Machine-learned classification emphasizes snowballs or snowbanks while excluding systemic causes such as multiple sclerosis, sarcoidosis, and syphilis.
  evidence:
  - reference: PMID:33845006
    supports: SUPPORT
    snippet: "Key criteria for pars planitis included unilateral or bilateral intermediate uveitis with either 1) snowballs in the vitreous or 2) snowbanks on the pars plana."
    explanation: Provides the core SUN Working Group criteria that define pars planitis among intermediate uveitides.
- name: Aqueous Humor Exosome Profiling
  presence: Positive
  notes: Large 90-120 nm exosome peaks in aqueous humor correlate with inflammatory pars planitis activity.
  evidence:
  - reference: PMID:38155415
    supports: SUPPORT
    snippet: "Flare-ups of large exosomes(size 90-120 nm)were found in the patients with the inflammatory ocular disease pars planitis."
    explanation: Demonstrates that exosome size distribution in aqueous humor can help identify inflammatory pars planitis.
genetic:
- name: HLA-DR15
  association: Risk Factor
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Associations between pars planitis and HLA-DR2, -DR15, -B51 and -DRB1*0802 haplotypes have been described suggesting an immunogenetic predisposition."
    explanation: HLA-DR15 has been linked to immunogenetic susceptibility in pars planitis.
- name: HLA-B51
  association: Risk Factor
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Associations between pars planitis and HLA-DR2, -DR15, -B51 and -DRB1*0802 haplotypes have been described suggesting an immunogenetic predisposition."
    explanation: HLA-B51 is reported among haplotypes associated with pars planitis, supporting a genetic component.
environmental:
- name: Arboviral Infection (Chikungunya)
  effect: Potential trigger
  notes: Arboviral infections such as chikungunya can present as intermediate uveitis and should be excluded before labeling idiopathic pars planitis.
  evidence:
  - reference: PMID:28010143
    supports: SUPPORT
    snippet: "Exam revealed a unilateral intermediate uveitis, with an extensive work-up positive for chikungunya virus immunoglobulin M and G titers."
    explanation: Demonstrates that chikungunya infection can manifest as intermediate uveitis, making viral screening important in suspected pars planitis.
- name: Systemic Infection Exclusion
  effect: Exclusion criterion
  notes: By definition pars planitis lacks an associated systemic infection; suspected cases warrant workup to rule out infectious causes before confirming idiopathic disease.
  evidence:
  - reference: PMID:28613790
    supports: SUPPORT
    snippet: "Pars planitis is chronic intermediate uveitis for which no systemic disease or associated infection could be found."
    explanation: Clarifies that absence of systemic infection is required to diagnose idiopathic pars planitis, guiding environmental trigger evaluation.
treatments:
- name: Corticosteroids
  description: First-line treatment for reducing inflammation in pars planitis.
  examples:
  - Subtenon triamcinolone injection
  - Intravitreal triamcinolone
  - Oral prednisone
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis."
    explanation: Corticosteroids form the foundation of treatment for pars planitis.
  treatment_term:
    preferred_term: pharmacotherapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    qualifiers:
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: triamcinolone
        term:
          id: NCIT:C901
          label: Triamcinolone
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: prednisone
        term:
          id: NCIT:C770
          label: Prednisone
- name: Immunosuppressive Agents
  description: Second-line therapy for chronic or steroid-resistant cases.
  examples:
  - Methotrexate
  - Mycophenolate mofetil
  - Azathioprine
  - Cyclosporine
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "Methotrexate is the most widely used first-line immunosuppressive agent in children with chronic non-infectious uveitis because of its long-term safety record and well tolerance."
    explanation: Immunosuppressive agents, particularly methotrexate, provide steroid-sparing control for chronic cases.
  treatment_term:
    preferred_term: pharmacotherapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    qualifiers:
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: methotrexate
        term:
          id: NCIT:C642
          label: Methotrexate
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: mycophenolate mofetil
        term:
          id: NCIT:C1468
          label: Mycophenolate Mofetil
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: azathioprine
        term:
          id: NCIT:C290
          label: Azathioprine
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: cyclosporine
        term:
          id: NCIT:C406
          label: Cyclosporine
- name: Biological Therapy
  description: TNF-alpha inhibitors for refractory cases.
  examples:
  - Adalimumab
  - Infliximab
  evidence:
  - reference: PMID:34568953
    supports: SUPPORT
    snippet: "ADA was initiated in 23 patients (38.9%) due to refractory uveitis and adverse effects to the corticosteroid and helped control intraocular inflammation and decrease the use of systemic steroids/immunosuppressives in 22 of 23 (95%) of patients who received ADA."
    explanation: TNF-alpha inhibition with adalimumab controlled inflammation and enabled steroid-sparing in refractory cases.
  treatment_term:
    preferred_term: pharmacotherapy
    term:
      id: MAXO:0000058
      label: pharmacotherapy
    qualifiers:
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: adalimumab
        term:
          id: NCIT:C65216
          label: Adalimumab
    - predicate:
        preferred_term: therapeutic agent
        term:
          id: NCIT:C2259
          label: Therapeutic Agent
      value:
        preferred_term: infliximab
        term:
          id: NCIT:C1789
          label: Infliximab
- name: Pars Plana Vitrectomy
  description: Surgical intervention for severe vitreous opacities or complications.
  evidence:
  - reference: PMID:27051493
    supports: SUPPORT
    snippet: "A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis."
    explanation: Surgical intervention may be necessary for cases with severe vitreous involvement or complications.
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: MAXO:0000004
      label: surgical procedure
differential_diagnoses:
- name: Birdshot Retinochoroiditis
  description: Retinal vasculitis with HLA-A29 positivity can mimic intermediate uveitis but has a distinct angiographic signature.
  distinguishing_features:
  - Scoring of retinal vasculitis features such as disc hyperfluorescence and profuse posterior leakage separates birdshot retinochoroiditis from pars planitis.
  - Confirmation of HLA-A29 antigen supports birdshot retinochoroiditis, whereas pars planitis has no HLA antigen requirement.
  disease_term:
    preferred_term: birdshot chorioretinopathy
    term:
      id: MONDO:0011599
      label: birdshot chorioretinopathy
  evidence:
  - reference: PMID:40642353
    supports: SUPPORT
    snippet: "HLA-A29 antigen was present in all patients (100%)."
    explanation: Confirms the defining HLA-A29 positivity used to differentiate birdshot retinochoroiditis from pars planitis in comparative cohorts.
  - reference: PMID:40642353
    supports: SUPPORT
    snippet: "Retinal vasculitis related to BRC has specific findings leading, if present, to the diagnosis of BRC that should be ascertained by the search of indocyanine green angiography lesions with the ultimate confirmation by the presence of the HLA-A29 antigen."
    explanation: Specific vasculitis features plus HLA-A29 confirmation distinguish birdshot retinochoroiditis from pars planitis.
- name: Retinoblastoma (Masquerade Syndrome)
  description: Retinoblastoma can present with vitreous seeding and mimic inflammatory vitreous snowballs seen in pars planitis.
  distinguishing_features:
  - Presence of an intraocular mass with diffuse vitreous seeding rather than inflammatory snowballs.
  - Regression with intra-arterial or intravitreal chemotherapy instead of corticosteroid or immunosuppressive therapy.
  disease_term:
    preferred_term: retinoblastoma
    term:
      id: MONDO:0008380
      label: retinoblastoma
  evidence:
  - reference: PMID:41334298
    supports: SUPPORT
    snippet: "Fundus examination with indirect ophthalmoscopy at our center revealed a fundus mass with diffuse vitreous seeding."
    explanation: Demonstrates that a fundus mass with vitreous seeding signals retinoblastoma rather than inflammatory pars planitis.
- name: Infectious Masquerade Intermediate Uveitis
  description: Infectious entities can mimic intermediate uveitis presentations and must be excluded before diagnosing idiopathic pars planitis.
  distinguishing_features:
  - PCR testing and directed serologies identify infectious causes rather than idiopathic inflammation.
  - Targeted antimicrobial therapy improves infectious masquerade syndromes, unlike corticosteroid-responsive pars planitis.
  evidence:
  - reference: PMID:39360991
    supports: SUPPORT
    snippet: "PCR testing has enhanced the ability to diagnose infectious and neoplastic conditions that masquerade as intermediate uveitis."
    explanation: Shows that molecular testing uncovers infectious causes that can mimic pars planitis.
- name: Intraocular Lymphoma (Masquerade Syndrome)
  description: Primary intraocular lymphoma can imitate intermediate uveitis with vitreous cells and requires oncologic evaluation.
  distinguishing_features:
  - Presence of malignant lymphoid cells in ocular fluid or tissue differentiates lymphoma from idiopathic inflammation.
  - Responds to oncologic therapy rather than corticosteroids alone.
  disease_term:
    preferred_term: intraocular lymphoma
    term:
      id: MONDO:0004351
      label: intraocular lymphoma
  evidence:
  - reference: PMID:39360991
    supports: SUPPORT
    snippet: "Etiology can be infectious, associated with a systemic disease, neoplastic or idiopathic."
    explanation: Notes that neoplastic causes such as intraocular lymphoma can masquerade as intermediate uveitis and must be excluded.
- name: Multiple Sclerosis-Associated Intermediate Uveitis
  description: Intermediate uveitis secondary to multiple sclerosis can resemble pars planitis but carries neurologic signs and demyelinating lesions.
  distinguishing_features:
  - Neurologic symptoms and MRI-demonstrated demyelinating lesions support multiple sclerosis-associated uveitis rather than idiopathic pars planitis.
  - Workup for demyelinating disease is required when intermediate uveitis co-occurs with neurologic complaints.
  disease_term:
    preferred_term: multiple sclerosis
    term:
      id: MONDO:0005301
      label: multiple sclerosis
  evidence:
  - reference: PMID:33845006
    supports: SUPPORT
    snippet: "Key exclusions included: 1) multiple sclerosis, 2) sarcoidosis, and 3) syphilis."
    explanation: The SUN criteria treat multiple sclerosis as an exclusion, underscoring the need to differentiate it from idiopathic pars planitis.
- name: Sarcoidosis-Associated Intermediate Uveitis with Vasoproliferative Tumor
  description: Sarcoidosis-related intermediate uveitis can produce peripheral vasoproliferative tumors and exudative detachment, mimicking complicated pars planitis.
  distinguishing_features:
  - Systemic sarcoidosis history with granulomatous uveitis plus a peripheral retinal vascular mass points to sarcoid-associated intermediate uveitis rather than idiopathic pars planitis.
  - Exudative retinal detachment arising from a vasoproliferative tumor that regresses with combined steroid-sparing immunosuppression, vitrectomy, and tumor-directed cryotherapy distinguishes this entity.
  disease_term:
    preferred_term: sarcoidosis
    term:
      id: MONDO:0019338
      label: sarcoidosis
  evidence:
  - reference: PMID:38645965
    supports: SUPPORT
    snippet: "She had active vitritis, and a peripheral retinal vascular mass was noted in the superotemporal periphery. The mass was associated with ERD involving the posterior pole."
    explanation: Highlights sarcoidosis-associated intermediate uveitis complicated by vasoproliferative tumor and exudative detachment, requiring differentiation from idiopathic pars planitis.
disease_term:
  preferred_term: pars planitis
  term:
    id: MONDO:0011644
    label: pars planitis