Clinical and morphological features of Waardenburg syndrome type II

A comprehensive genotype-phenotype evaluation of eight Chinese probands with Waardenburg syndrome

Background

Waardenburg syndrome (WS) is the most common form of syndromic deafness with phenotypic and genetic heterogeneity in the Chinese population. This study aimed to clarify the clinical characteristics and the genetic cause in eight Chinese WS families (including three familial and five sporadic cases). Further genotype–phenotype relationships were also investigated.

Methods

All probands underwent screening for the known WS-related genes including PAX3, SOX10, MITF, EDNRB, EDN3, and SNAI2 using next-generation sequencing to identify disease-causing genes. Further validation using Sanger sequencing was performed. Relevant findings for the associated genotype–phenotype from previous literature were retrospectively analyzed.

Result

Disease-causing variants were detected in all eight probands by molecular genetic analysis of the WS genes (SOX10(NM_006941.4): c.544_557del, c.553 C > T, c.762delA, c.336G > A; MITF(NM_000248.3): c.626 A > T; PAX3(NM_181459.4): c.838delG, c.452-2 A > G, c.214 A > G). Six mutations (SOX10:c.553 C > T, c.544_557del, c.762delA; PAX3: c.838delG, c.214 A > G; MITF:c.626 A > T) were first reported. Clinical evaluation revealed prominent phenotypic variability in these WS patients. Twelve WS1 cases and five WS2 cases were diagnosed in total. Two probands with SOX10 mutations developed progressive changes in iris color with age, returning from pale blue at birth to normal tan. Additionally, one proband had a renal malformation (horseshoe kidneys).All cases were first described as WS cases. Congenital inner ear malformations were more common, and semicircular malformations were exclusively observed in probands with SOX10 mutations. Unilateral hearing loss occurred more often in cases with PAX3 mutations.

Conclusion

Our findings helped illuminate the phenotypic and genotypic spectrum of WS in Chinese populations and could contribute to better genetic counseling of WS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01379-6.

A novel mutation of the StAR gene with congenital adrenal hyperplasia and its association with heterochromia iridis: a case report

BACKGROUND

We report a novel mutation within the StAR gene, causing congenital adrenal hyperplasia, with the so far unreported association with heterochromia iridis.

CASE PRESENTATION

In a now 15-year-old girl (born at 41 + 6 weeks of gestation) adrenal failure was diagnosed in the neonatal period based on the clinical picture with spontaneous hypoglycaemia, hyponatremia and an extremely elevated concentration of ACTH (3381 pmol/l; ref. level 1,1-10,1 pmol/l), elevated renin (836 ng/l; ref. level 5-308 ng/l), and a decreased concentration of aldosterone (410 pmol/l; ref. level 886-3540 pmol/l). In addition to hyperpigmented skin the patient exhibited sectorial heterochromia iridis. Sequence analysis of the steroidogenic acute regulatory protein (StAR) gene showed a novel homozygous mutation (c.652G > A (p.Ala218Thr), which was predicted in-silico to be possibly damaging. Under daily steroid substitution her electrolyte levels are balanced while she became obese. Puberty occurred spontaneously.

CONCLUSION

A novel mutation in the StAR gene was identified in a patient with severe adrenal hypoplasia and sectorial heterochromia iridis. We discuss a causal relationship between these two rare phenotypes, i.e. whether very high levels of ACTH and alpha-MSH during early development might have disturbed early differentiation and distribution of uveal melanocytes. If confirmed in additional cases, discolorization of the iris might be considered as an additional phenotypical feature in the differential diagnosis of congenital adrenal insufficiency.

Choroidal thickness in Waardenburg syndrome

Purpose: To assess the choroidal thickness in differently pigmented areas of the fundus in a 46-year-old female with Waardenburg syndrome. Methods: Retrospective, case review. Choroidal thickness was measured using swept-source optical coherence tomography (SS-OCT, Topcon DRI OCT-1 Atlantis) and compared between the pigmented and hypopigmented areas within the same eye and between the two eyes. Results: Best corrected visual acuity (BCVA) was 20/20 in both eyes. The right fundus had a variegated appearance without choroidal hypopigmentation. The left fundus had choroidal hypopigmentation beyond the superotemporal arcade up to the periphery. Subfoveal choroidal thickness was 455 µ in the right eye and 569 µ in the left eye. In the left eye, the comparison of two equidistant points from the foveola along a radial scan passing through the superotemporal hypopigmented area revealed a thinner choroidal thickness (457 µ) compared to the corresponding point in the pigmented inferonasal quadrant (591 µ). Conclusion: Choroidal thickness is decreased in the hypopigmented area of the fundus compared to the pigmented area in subjects with Waardenburg syndrome. The overall thickness of the choroid in such eyes could still be more than the mean value in the normal population.

CHOROIDAL MELANOMA IN A PATIENT WITH WAARDENBURG SYNDROME

PURPOSE

To report a case of choroidal malignant melanoma in a patient with Waardenburg syndrome and bilateral choroidal pigmentary abnormalities.

METHODS

Clinical examination and multimodal imaging of the case.

RESULTS

A 45-year-old woman presented with asymptomatic flat choroidal pigmentation abnormalities in both eyes. A choroidal lesion was identified in the inferotemporal periphery of the left eye arising from an area of hyperpigmentation; ultrasonography findings were consistent with a choroidal melanoma. The patient endorsed a personal and family history of premature graying of hair and was identified to have dystopia canthorum consistent with the diagnosis of Waardenburg syndrome.

CONCLUSION

The authors present the first reported case of concurrent Waardenburg syndrome and choroidal malignant melanoma. This cooccurrence may suggest that the relative hyperpigmented regions in affected fundi may be abnormal and should be monitored closely for the development of choroidal melanoma.

Don't it make my blue eyes brown: heterochromia and other abnormalities of the iris

Eye colour is one of the most important characteristics in determining facial appearance. In this paper I shall discuss the anatomy and genetics of normal eye colour, together with a wide and diverse range of conditions that may produce an alteration in normal iris pigmentation or form.

Intraocular pressure change in orbital disease

Intraocular pressure change has been found concurrent with many orbital pathologies, particularly those involving proptosis. The objective of this review is to offer an inclusive classification of orbital disease-related intraocular pressure change, not only for oculoplastics and glaucoma specialists, but also for general ophthalmologists. Various orbital conditions associated with increased intraocular pressure and glaucoma are comprehensively summarized, and pathophysiology, clinical manifestations, and treatment options of these diseases are discussed. Graves disease, arterio-venous shunts, trauma, and orbital neoplasia, and other common conditions are discussed in detail; less frequent syndromes such as orbitocraniofacial deformities, phakomatoses, and mucopolysaccharidoses are included for the sake of comprehensiveness, but discussed less extensively.

Waardenburg syndrome in four Mexican patients

Waardenburg syndrome is a hereditary auditory-pigmentary syndrome. The major features include pigmentary disturbances and congenital deafness. Clinical findings are extremely variable, not only at the authors' institution but also in the literature. The authors describe four patients who presented with various clinical features and different genetic pedigree penetration.

Insights into melanosomes and melanin from some interesting spatial and temporal properties

Melanosomes are organelles found in a wide variety of tissues throughout the animal kingdom and exhibit a range of different shapes: spheres of up to approximately 1 mum diameters and ellipsoids with lengths of up to approximately 2 mum and varying aspect ratios. The functions of melanosomes include photoprotection, mitigation of the effects of reactive oxygen species, and metal chelation. The melanosome contains a variety of biological molecules, e.g., proteins and lipids, but the dominant constituent is the pigment melanin, and the functions ascribed to melanosomes are uniquely enabled by the chemical properties of the melanins they contain. In the past decade, there has been significant progress in understanding melanins and their impact on human health. While the molecular details of melanin production and how the pigment is organized within the melanosome determine its properties and biological functions, the physical and chemical properties of the surface of the melanosome are central to their range of ascribed functions. Surprisingly, few studies designed to probe this biological surface have been reported. In this article, we discuss recent work using surface-sensitive analytic, spectroscopic, and imaging techniques to examine the structural and chemical properties of many types of natural pigments: sepia melanin granules, human and bovine ocular melanosomes, human hair melanosomes, and neuromelanin. N 2 adsorption/desorption measurements and atomic force microscopy provide novel insights into surface morphology. The chemical properties of the melanins present on the surface are revealed by X-ray photoelectron spectroscopy and photoemission electron microscopy. These technologies are also applied to elucidate changes in surface properties that occur with aging. Specifically, studies of the surface properties of human retinal pigment epithelium melanosomes as a function of age are stimulating the development of models for their age-dependent behaviors. The article concludes with a brief discussion of important unanswered research questions in this field.

Distant regulatory elements in a Sox10-beta GEO BAC transgene are required for expression of Sox10 in the enteric nervous system and other neural crest-derived tissues

Sox10 is an essential transcription factor required for development of neural crest-derived melanocytes, peripheral glia, and enteric ganglia. Multiple transcriptional targets regulated by Sox10 have been identified; however, little is known regarding regulation of Sox10. High sequence conservation surrounding 5' exons 1 through 3 suggests these regions might contain functional regulatory elements. However, we observed that these Sox10 genomic sequences do not confer appropriate cell-specific transcription in vitro when linked to a heterologous reporter. To identify elements required for expression of Sox10 in vivo, we modified bacterial artificial chromosomes (BACs) to generate a Sox10betaGeoBAC transgene. Our approach leaves endogenous Sox10 loci unaltered, circumventing haploinsufficiency issues that arise from gene targeting. Sox10betaGeoBAC expression closely approximates Sox10 expression in vivo, resulting in expression in anterior dorsal neural tube at embryonic day (E) 8.5 and in cranial ganglia, otic vesicle, and developing dorsal root ganglia at E10.5. Characterization of Sox10betaGeoBAC expression confirms the presence of essential regulatory regions and additionally identifies previously unreported expression in thyroid parafollicular cells, thymus, salivary, adrenal, and lacrimal glands. Fortuitous deletions in independent Sox10betaGeoBAC lines result in loss of transgene expression in peripheral nervous system lineages and coincide with evolutionarily conserved regions. Our analysis indicates that Sox10 expression requires the presence of distant cis-acting regulatory elements. The Sox10betaGeoBAC transgene offers one avenue for specifically testing the role of individual conserved regions in regulation of Sox10 and makes possible analysis of Sox10+ derivatives in the context of normal neural crest development.

Comparisons of the Structural and Chemical Properties of Melanosomes Isolated from Retinal Pigment Epithelium, Iris and Choroid of Newborn and Mature Bovine Eyes¶

Melanosomes were isolated from the retinal pigment epithelium (RPE), iris and choroid of mature (age >2 years) and newborn (age <1 week) bovine eyes. Scanning electron microscopy was utilized to analyze the morphology of the melanosomes, which were found to vary among different tissues and different ages. While the total content of amino acids differs slightly (ranging from 9% to 15% by mass), the distributions of the amino acids are similar. The pheomelanin content is low in the choroid and the RPE (0.1-0.5%), and moderate in the iris (<2%); therefore, the major melanin component of bovine eye melanosomes is eumelanin, independent of the shape of the melanosomes. The yields of pyrrole-2,3,5-tricarboxylic acid from melanosomes decrease in the following order: choroid > iris > RPE, and exhibit decreasing yields with age. 13C solid-state nuclear magnetic resonance (NMR) spectroscopic analysis of iris and choroid melanosomes indicates the same trends. These observations suggest that the 5,6-dihydroxyindole-2-carboxylic acid contents decrease in the following order: choroid > iris > RPE, and decrease with age. Moreover, the 13C solid-state NMR spectra show (1) for the same age samples, the CH:Cq ratio for choroid is larger than that for iris melanosomes; and (2) an increase in the concentration of carbonyl groups with age within each type of melanosome.

When the darker eye has the smaller pupil

Waardenburg and congenital Horner syndromes are both recognized causes of congenital hypochromic iris heterochromia. Each has been linked to disruptions in the pathway of tyrosinase induction, thus leading to a deficiency in melanin production of the iris. These syndromes must be considered in the differential diagnosis of a patient presenting with heterochromia iridis. We present the case of a 20-month old boy afflicted with both congenital Horner syndrome and Waardenburg syndrome, type II. In contrast to the more common presentation of congenital Horner syndrome, the affected iris in this case was the darker of the two because of the effects of the concomitant Waardenburg syndrome on the contralateral iris pigmentation. We are unaware of any other cases presenting with both Horner and Waardenburg syndromes and believe that this case serves as an excellent opportunity to briefly review the pathophysiology involved with these disorders.

Cataract and hearing loss in a population-based study: the Beaver Dam studies

PURPOSE

Cataract and hearing loss are each common at older ages and together may influence the ability to function independently and affect the sense of well-being. For these reasons, we sought to estimate the risk factors for comorbidity of age-related cataract and hearing loss.

METHODS

A cross-sectional evaluation of a population-based cohort of older adults was conducted in Beaver Dam, Wisconsin, for presence of age-related cataract and hearing loss. The study evaluation included taking standardized medical histories, measuring blood pressures, and obtaining blood specimens. Standardized photographs, which were graded according to well-defined protocols to assess the presence of nuclear, cortical or posterior subcapsular cataract, were taken. Audiometric testing was performed according to well-defined study protocols.

RESULTS

Any type of cataract in combination with hearing loss in either ear was frequent, occurring in 27.8% of the population overall and increasing consistently with age. Nuclear and posterior subcapsular cataract in combination with hearing loss occurred more often in men. Lifestyle factors that were associated with at least one cataract-hearing loss end point in at least one sex were history of heavy drinking and smoking.

CONCLUSIONS

In this community, older adults appear to be at high risk of cataract and hearing loss. Although risk is strongly associated with age, some elective exposures appear to influence risk. It is possible that modification of certain lifestyle habits may alter these risks.