The Heritability of Pigment Dispersion Syndrome and Pigmentary Glaucoma

Genetic Basis of Pigment Dispersion Syndrome and Pigmentary Glaucoma: An Update and Functional Insights

Pigment Dispersion Syndrome (PDS) and Pigmentary Glaucoma (PG) comprise a spectrum of ocular disorders characterized by iris pigment dispersion and trabecular meshwork changes, resulting in increased intraocular pressure and potential glaucomatous optic neuropathy. This review summarizes recent progress in PDS/PG genetics including rare pathogenic protein coding alterations (PMEL) and susceptibility loci identified from genome-wide association studies (GSAP and GRM5/TYR). Areas for future research are also identified, especially the development of efficient model systems. While substantial strides have been made in understanding the genetics of PDS/PG, our review identifies key gaps and outlines the future directions necessary for further advancing this important field of ocular genetics.

Secondary glaucoma: Toward interventions based on molecular underpinnings

Glaucoma is a heterogeneous group of progressive diseases that leads to irreversible blindness. Secondary glaucoma refers to glaucoma caused by a known underlying condition. Pseudoexfoliation and pigment dispersion syndromes are common causes of secondary glaucoma. Their respective deposits may obstruct the trabecular meshwork, leading to aqueous humor outflow resistance, ocular hypertension, and optic neuropathy. There are no disease-specific interventions available for either. Pseudoexfoliation syndrome is characterized by fibrillar deposits (pseudoexfoliative material) on anterior segment structures. Over a decade of multiomics analyses taken together with the current knowledge on pseudoexfoliative glaucoma warrant a re-think of mechanistic possibilities. We propose that the presence of nucleation centers (e.g., vitamin D binding protein), crosslinking enzymes (e.g., transglutaminase 2), aberrant extracellular matrix, flawed endocytosis, and abnormal aqueous-blood barrier contribute to the formation of proteolytically resistant pseudoexfoliative material. Pigment dispersion syndrome is characterized by abnormal iridolenticular contact that disrupts iris pigment epithelium and liberates melanin granules. Iris melanogenesis is aberrant in this condition. Cytotoxic melanogenesis intermediates leak out of melanosomes and cause iris melanocyte and pigment epithelium cell death. Targeting melanogenesis can likely decrease the risk of pigmentary glaucoma. Skin and melanoma research provides insights into potential therapeutics. We propose that specific prostanoid agonists and fenofibrates may reduce melanogenesis by inhibiting cholesterol internalization and de novo synthesis. Additionally, melatonin is a potent melanogenesis suppressor, antioxidant, and hypotensive agent, rendering it a valuable agent for pigmentary glaucoma. In pseudoexfoliative glaucoma, where environmental insults drive pseudoexfoliative material formation, melatonin's antioxidant and hypotensive properties may offer adjunct therapeutic benefits. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

The Geographical Impact of Plastic Surgery Residency to Fellowship and Residency/Fellowship to First Job Placement

INTRODUCTION

The location of trainees' plastic surgery residency or fellowship has implications on their subsequent careers, which can inform future trainees and faculty decisions, and may affect access to care nationwide. This study explores historic geographic trends of the location where trainees complete residency or fellowship and where they pursue a fellowship program or first job.

METHODS

Graduates from US integrated plastic surgery residency or fellowship programs from 2015 to 2021 were identified along with their proximity to fellowship or first job. Location was categorized based on whether the graduate's fellowship/first job location to residency/fellowship was within 100 miles, the same state, the same geographic region, the United States, or international. A χ2 value was calculated to determine the significance of relative geographical location after training.

RESULTS

Three hundred sixty-five graduates that attended fellowship were included, representing 76.5% (65/85) of integrated plastic surgery residency programs. There were 47.7% (n = 174) that stayed within the same geographic region and 3.6% (n = 13) pursued training internationally. The location of the residency or fellowship program appears to have an influence on the location of the graduate's fellowship or first job.

CONCLUSION

Graduates who completed integrated residency or fellowship in a certain geographic location were more likely to stay in that area for their fellowship or first job. This may be explained by graduates continuing training with their original program, the established network, and personal factors such as family and friends.

Pigment dispersion syndrome and pigmentary glaucoma: overview and racial disparities

Pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) are two stages within the same ophthalmic disease spectrum, which are known to be affected by race. The prevalence of PDS is underestimated, largely due to its minor clinical symptoms. Although the prevalence of PG is low, the visual impairment associated with PG is extremely severe. The prevalence of PDS-PG is four or more times higher in Caucasians than in Blacks or Asians, and the "classic" PDS in Caucasians has long been used as a benchmark diagnostic criterion. Following extensive research focused on African Americans and Asians, the standard for diagnosing PDS-PG was refined. At the same time, the pathogenesis of PDS is not the same in different races. Hence, the effectiveness of preventive treatment and the need for treatment may not be equivalent in different races. The rate of conversion of PDS to PG is nearly 1/3 in Caucasians and higher in blacks and Asians, requiring more aggressive treatment and monitoring. We systematically searched a PubMed database from inception to March 2022 to provide an overview of research progress in various aspects of PDS-PG. Specifically, this paper considers the effects of race on disease prevalence, clinical manifestation, diagnostic criteria, disease mechanism, hereditary traits, treatment, and prevention to provide an accurate and comprehensive guide for the diagnosis and treatment of PDS-PG in various races.

Axenfeld-Rieger syndrome combined with ectropion uveae and pigment dispersion syndrome: A case report

BACKGROUND

In January 2021, we found one case of Axenfeld-Rieger syndrome combined with pigment dispersion syndrome (PDS), and this patient additionally manifested a symptom of ectropion uveae. The co-existence of both 2 syndromes is very rare and has not been reported in any literature yet.

CASE PRESENTATION

A 34-year-old female truck driver presented to our institution with a dimness of vision in her right eye. The patient had obvious posterior embryotoxons at bitamporal, and peripheral anterior synechia could be visualized by the slit lamp. The dispersion of pigment granules was observed behind the cornea. The pupil was slightly shifted upwards the nose, with 360° ectropion uveae. Gonioscopy revealed pigment accumulation on the trabecular meshwork. The patient underwent cataract surgery on her right eye, during which, flaky pigmentation around the posterior capsule was observed. These signs were consistent with Axenfeld-Rieger syndrome and PDS.

CONCLUSIONS

We report a rare case of Axenfeld-Rieger syndrome with PDS and uveal eversion. Although the patient did not present with glaucoma, follow-up should be noted. Besides, the correlation between these 2 syndromes needs to be demonstrated by more cases or further evidence.

Compound Heterozygous Variants of the CPAMD8 Gene Co-Segregating in Two Chinese Pedigrees With Pigment Dispersion Syndrome/Pigmentary Glaucoma

The molecular mechanisms underlying the pathogenesis of pigment dispersion syndrome and pigmentary glaucoma remain unclear. In pedigree-based studies, familial aggregation and recurrences in relatives suggest a strong genetic basis for pigmentary glaucoma. In this study, we aimed to identify the genetic background of two Chinese pedigrees with pigmentary glaucoma. All members of these two pedigrees who enrolled in the study underwent a comprehensive ophthalmologic examination, and genomic DNA was extracted from peripheral venous blood samples. Whole-exome sequencing and candidate gene verifications were performed to identify the disease-causing variants; in addition, screening of the CPAMD8 gene was performed on 38 patients of sporadic pigmentary glaucoma. Changes in the structure and function of abnormal proteins caused by gene variants were analyzed with a bioinformatics assessment. Pigmentary glaucoma was identified in a total of five patients from the two pedigrees, as were compound heterozygous variants of the CPAMD8 gene. No signs of pigmentary glaucoma were found in carriers of monoallelic CPAMD8 variant/variants. All four variants were inherited in an autosomal recessive mode. In addition to the 38 patients of sporadic pigmentary glaucoma, 13 variants of the CPAMD8 gene were identified in 11 patients. This study reported a possible association between CPAMD8 variants and pigment dispersion syndrome/pigmentary glaucoma.

A transcriptome atlas of the mouse iris at single-cell resolution defines cell types and the genomic response to pupil dilation

The iris controls the level of retinal illumination by controlling pupil diameter. It is a site of diverse ophthalmologic diseases and it is a potential source of cells for ocular auto-transplantation. The present study provides foundational data on the mouse iris based on single nucleus RNA sequencing. More specifically, this work has (1) defined all of the major cell types in the mouse iris and ciliary body, (2) led to the discovery of two types of iris stromal cells and two types of iris sphincter cells, (3) revealed the differences in cell type-specific transcriptomes in the resting vs. dilated states, and (4) identified and validated antibody and in situ hybridization probes that can be used to visualize the major iris cell types. By immunostaining for specific iris cell types, we have observed and quantified distortions in nuclear morphology associated with iris dilation and clarified the neural crest contribution to the iris by showing that Wnt1-Cre-expressing progenitors contribute to nearly all iris cell types, whereas Sox10-Cre-expressing progenitors contribute only to stromal cells. This work should be useful as a point of reference for investigations of iris development, disease, and pharmacology, for the isolation and propagation of defined iris cell types, and for iris cell engineering and transplantation.

Exome-based investigation of the genetic basis of human pigmentary glaucoma

Background

Glaucoma is a leading cause of visual disability and blindness. Release of iris pigment within the eye, pigment dispersion syndrome (PDS), can lead to one type of glaucoma known as pigmentary glaucoma. PDS has a genetic component, however, the genes involved with this condition are largely unknown. We sought to discover genes that cause PDS by testing cohorts of patients and controls for mutations using a tiered analysis of exome data.

Results

Our primary analysis evaluated melanosome-related genes that cause dispersion of iris pigment in mice (TYRP1, GPNMB, LYST, DCT, and MITF). We identified rare mutations, but they were not statistically enriched in PDS patients. Our secondary analyses examined PMEL (previously linked with PDS), MRAP, and 19 other genes. Four MRAP mutations were identified in PDS cases but not in controls (p = 0.016). Immunohistochemical analysis of human donor eyes revealed abundant MRAP protein in the iris, the source of pigment in PDS. However, analysis of MRAP in additional cohorts (415 cases and 1645 controls) did not support an association with PDS. We also did not confirm a link between PMEL and PDS in our cohorts due to lack of reported mutations and similar frequency of the variants in PDS patients as in control subjects.

Conclusions

We did not detect a statistical enrichment of mutations in melanosome-related genes in human PDS patients and we found conflicting data about the likely pathogenicity of MRAP mutations. PDS may have a complex genetic basis that is not easily unraveled with exome analyses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07782-0.

Pigmentdispersionssyndrom

Das Pigmentdispersionssyndrom ist eine Erkrankung, die durch Abschilferung von Pigment aus dem Irispigmentepithel und dessen Ablagerung im vorderen Augenabschnitt charakterisiert ist. Typisch ist eine Trias aus Ablagerungen am Hornhautendothel, zirkulären Iristransilluminationen und einer Pigmentierung des Trabekelwerks. Das Spektrum reicht vom einfachen Pigmentdispersionssyndrom bis zum Pigmentdispersionsglaukom mit Optikusatrophie.

[Pigment Dispersion Syndrome]

Pigment dispersion syndrome (PDS) is a disorder predominantly affecting young, myopic adults. It is characterised by the liberation of pigment of the iris and deposition of it on various structures of the anterior segment leading to multiple specific findings in slit lamp examination. Typical alterations are a deposition of pigment on the central corneal endothelium, circular iris transillumination defects in the mid periphery, a posterior bowing of the iris and increased pigmentation of the trabecular meshwork. Findings are usually bilateral symmetric. Posterior bowing of the iris causes rubbing of the pigmented iris epithelium against lens structures like zonular fibres with a consecutive liberation of pigment. Trabecular meshwork changes because of pigment deposition reduce aqueous outflow facility with the risk of elevated intraocular pressure and glaucoma. Pigmentary glaucoma (PG) is a secondary open angle glaucoma. Treatment of PG is similar to primary open angle glaucoma, including medical therapy, laser therapy and surgery. Peripheral laser iridotomy was shown to change iris configuration but its efficacy in the prevention of PG has not been confirmed in the literature. The purpose of this paper is to summarize information regarding ocular manifestations of PDS to facilitate an early diagnosis and to present a general view of the treatment of PG.

Pigment dispersion syndrome and its implications for glaucoma

Pigment dispersion syndrome (PDS) represents a clinical spectrum of a relatively common and usually underdiagnosed phenomenon produced by spontaneous pigment dispersion from the iris into the anterior segment. PDS is often bilateral, has no gender predisposition, and presents at a young age, particularly in myopes. Although most patients experiencing an episode of pigment dispersion are asymptomatic, extreme photophobia, ocular pain, redness, and blurred vision may occur. Other characteristic signs are iridolenticular contact, concave iris configuration, 360° peripheral iris transillumination, and pigment deposition on the anterior chamber angle or the corneal endothelium (Krukenberg spindle). Early PDS diagnosis is crucial to detect patients with pigment-related ocular hypertension (POHT) that can eventually lead to pigmentary glaucoma (PG). The latter represents a sight-threatening condition in which mechanical, environmental, and genetic factors contribute to optic nerve damage. In this review, we update the pathogenic mechanisms involved in the clinical spectrum of the disease. We describe its clinical presentation, ophthalmologic manifestations, and complications, including the factors influencing the development of POHT and PG. Because PDS has variable clinical presentations that lead to misdiagnoses, we emphasize the differential diagnosis and the actual therapeutic strategies according to disease status.

A case of dense pigment deposition of the posterior lens capsule

BACKGROUND

Pigment dispersion syndrome (PDS) is a well-known entity which can lead to pigmentary glaucoma (PG). This case report presents a rare presentation of PG with bilateral dense pigment deposits of the posterior lens capsule.

CASE PRESENTATION

A 72-year-old male came for his first appointment due to an asymmetric worsening of visual acuity. The examination showed unilaterally severely increased intraocular pressure, bilateral dense pigment deposition of the posterior lens capsule, and a shallow unilateral optic disk excavation. Gonioscopy revealed moderate pigmentation of the angle and a concave configuration of the peripheral iris in both eyes. The standard slit lamp examination showed no transillumination defects of either iris. Optical coherence tomography showed retinal nerve fiber layer (RNFL) thinning in the peripapillary and macular regions. An antiglaucoma medication was prescribed with a good lowering effect.

CONCLUSION

Pigment deposition of the posterior lens capsule, which has been rarely reported, is a possible important sign of PDS or PG.