Classic pars planitis: strong correlation of class II genes with gender and some clinical features in Mexican mestizos

Pediatric Pars Planitis: A Review

PURPOSE

To provide an overview of pediatric pars planitis.

METHODS

Narrative literature review.

RESULTS

Pars planitis refers to the idiopathic subset of intermediate uveitis in which there is vitritis along with snowball or snowbank formation occurring in the absence of an associated infection or systemic disease. It is thought to be a T-cell mediated disease with a genetic predisposition. Pars planitis accounts for 5-26.7% of pediatric uveitis cases. Presentation is commonly bilateral but asymmetric, often with insidious onset of floaters and blurred vision. Although pars planitis is known to be a benign form of uveitis in most cases, severe complications secondary to chronic inflammation may arise, with cystoid macular edema being the most common cause of visual morbidity. Mild vitritis in the absence of symptoms, vision loss, or macular edema may be observed. Patients with severe vitritis and/or associated vision-threatening complications require prompt aggressive treatment. A stepladder approach including corticosteroids, immunosuppressive 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.

CONCLUSION

Timely diagnosis and adequate treatment of pediatric pars planitis and associated complications are crucial in order to improve visual outcomes.

Immunopathogenic Background of Pars Planitis

Pars planitis is defined as an intermediate uveitis of unknown background of systemic disease with characteristic formations such as vitreous snowballs, snowbanks and changes in peripheral retina. The incidence of pars planitis varies 2.4–15.4 % of the uveitis patients. The pathogenesis of the disease is to be determined in future. 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. T cells subsets play an important role as a memory-effector peripheral cell. Snowbanks are formed as an effect of post inflammatory glial proliferation of fibrous astrocytes. There is also a genetic predisposition for pars planitis by human leukocyte antigen and several other genes. A coexistence of multiple sclerosis and optic neuritis has been described in numerous studies. Epiretinal membrane, cataract, cystoid macular edema, retinal detachment, retinal vasculitis, neovascularization, vitreous peripheral traction, peripheral hole formation, vitreous hemorrhage, disc edema are common complications observed in pars planitis. There is a need to expand the knowledge of the pathogenic and immunologic background of the pars planitis to create an accurate pharmacological treatment.

Review of Intermediate Uveitis

The purpose of this article is to highlight evidence about the medical and surgical management of intermediate uveitis (IU). Updated understandings of the immunopathology of IU were reviewed in this retrospective literature review. Literature selection for this review was based on the PubMed database (National Library of Medicine) and OVID database (Wolters Kluwer). Articles deemed relevant were selected and highlighted. Intermediate uveitis is most often a benign form of uveitis. Since intermediate uveitis has been described in association with different systemic disorders, the initial diagnostic evaluation should serve to exclude masquerade syndromes and infectious diseases in which immunosuppression may be ineffective or contraindicated. Although the pathogenesis of intermediate uveitis is not fully understood, identification of proinflammatory molecules involved in the IU has contributed to the development and implementation of new therapies. Studies about the use of various immunosuppressants, biological agents and surgical treatment on IU have provided more evidence for managing IU. Nevertheless, corticosteroids remain the mainstay of treatment. The treatment options of intermediate uveitis are evolving, with the development of various immunosuppressants and biological agents. The management of intermediate uveitis should be tailored individually, based on specific causes of the disease and associated complications.

Intermediate uveitis and alopecia areata: is there a relationship? Report of 3 pediatric cases

Three previously healthy children, aged 5, 8, and 15 years, with idiopathic intermediate uveitis (IU) and alopecia areata (AA) are described. These are the first 3 cases of which we are aware with this coexistence. The results of extensive diagnostic evaluations were negative in all 3 cases. AA preceded the diagnosis of bilateral IU in 1 child and followed within several months after IU diagnosis in 2 children. The severity of uveitis ranged from mild to sight-threatening, and hair loss ranged from local lesions in 2 cases to total alopecia in 1 case. Pathogenesis of both diseases is discussed. Theoretically, the coexistence of IU and AA might be based on the similarities in their complex pathogenesis. However, more research is needed to evaluate if the coexistence is based on an association between 2 autoimmune disorders or is a coincidence.

An update on the genetics of HLA B27-associated acute anterior uveitis

The discovery of the association of HLA B27 with spondyloarthropathy led to more questions than answers about the role of this gene in disease susceptibility. The realization that HLA B27 was not responsible for all of the genetic effects helped to lay a foundation for further investigation into the genetics of uveitis. Over several decades, genetic findings have provided clues to advance the understanding of mechanisms of uveitis and to catalyze new research on diagnostics, animal models, and therapies. From the early candidate gene studies on immune mediators to the recent genome-wide investigations, much has been discovered. However, these discoveries have come with the caveat that a genetic finding does not automatically reveal the disease-relevant functional effect of the associated variant.

Common genetic determinants of uveitis shared with other autoimmune disorders

Uveitis is a complex multifactorial autoimmune disease of the eye characterized by inflammation of the uvea and retina, degeneration of the retina, and blindness in genetically predisposed patients. Using the rat model of experimental autoimmune uveitis (EAU), we previously identified three quantitative trait loci (QTL) associated with EAU on rat chromosomes 4, 12, and 10 (Eau1, Eau2, and Eau3). The primary goal of the current study is to delineate additional non-MHC chromosomal regions that control susceptibility to EAU, and to identify any QTLs that overlap with the QTLs of other autoimmune diseases. Using a set of informative microsatellite markers and F(2) generations of resistant and susceptible MHC class II-matched rat strains (F344 and LEW), we have identified several new significant or suggestive QTLs on rat chromosomes 2, 3, 7, 10, and 19 that control susceptibility to EAU. A protective allele was identified in the susceptible LEW strain in the Eau5 locus at D7Wox18, and epistatic interactions between QTLs were found to influence the severity of disease. The newly identified regions (Eau4 through Eau9) colocalize with the genetic determinants of other autoimmune disease models, and to disease-regulating syntenic regions identified in autoimmune patients on human chromosomes 4q21-31, 5q31-33, 16q22-24, 17p11-q12, 20q11-13, and 22q12-13. Our results suggest that uveitis shares some of the pathogenic mechanisms associated with other autoimmune diseases, and lends support to the "common gene, common pathway" hypothesis for autoimmune disorders.