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A kitten with a unilateral, congenital coloboma of the iris was raised in a normal environment and sacrificed at 6 monthlicted eye was seen in Nissl-stained sections taken through the lateral geniculate. The result suggests that image degradation is more important than luminance reduction in causing selective changes in the visual pathway.
PURPOSE: Investigate photoreceptor orientation and alignment in an observer with a simple coloboma of the iris and no retinal involvement. METHOD: Using a psychophysical procedure, extensive measurements of the Stiles-Crawford functions of the first kind (SCE I) were obtained from this observer. RESULTS: In this observer, the usual center-of-the-exit-pupil-of-the-eye alignment tendency of photoreceptors (inferred from the peaks of the SCE I functions) is absent. The inferred orientation of photoreceptors at numerous retinal loci tested lies outside the pupil, opposite the direction of the downwardly displaced pupil center. CONCLUSIONS: These results add support to previous suggestions that nonphototropic forces such as retinal tractional forces should be considered as an integral part of the mechanism(s) subserving human photoreceptor alignment in both normal and anomalous observers.
BACKGROUND: Paramacular coloboma (plural: colobomata) is a solitary oval football or torpedo-shaped chorioretinal lesion located temporal to the fovea in one or both eyes. Previous case reports have speculated varying etiology, but few have justified its pathognomonic shape and location. We believe it to be congenital in nature and caused by incomplete differentiation of the arcuate bundles along the horizontal raphe in development of the macular architecture. Associated ocular findings may include blepharophimosis, situs inversus, or other anomalous retinal vascular patterns. CASE REPORTS: Three cases of asymptomatic unilateral paramacular colobomata are presented. In each case, a single oval chorioretinal lesion temporal to the macula was found during routine examination. Visual acuity and Humphrey threshold visual field testing were normal with no other associated congenital, systemic, or ocular abnormalities. Because the lesion is nonprogressive, these patients can be followed on an annual basis. CONCLUSION: Due to their anatomical origin, paramacular colobomata are always located temporal to the macula and have an oval football-shaped appearance. Visual acuity and visual field testing are usually normal, although highly observant patients may be aware of a mild scotoma. Differential diagnosis is important because the clinical appearance can be similar to acquired conditions, most notably age-related macular degeneration and presumed ocular histoplasmosis syndrome.
Reported herein are the cases of two patients who developed subretinal neovascularization at the margin of a retinochoroidal coloboma. Possible explanations for the occurrence of this previously unemphasized association are addressed.
The association of Morning Glory anomaly with intracranial pathology has been rarely described and seems to be a distinct one. A 41-week full-term infant presenting with Morning Glory anomaly and multiple major and minor anomalies with a normal karyotype is described. Right Parieto-occipital porencephaly with mild hydrocephaly of lateral ventricle, right brain atrophy and enlarged thalami were observed by repeated ultrasound, computed tomography and magnetic resonance imaging examinations. Fundoscopy, visual evoked response and electroretinography revealed bilateral colobomas of the optic nerve, bilateral Morning Glory optic disc anomaly, severe exotropia and medial recti paralysis. Non-obstructive, non-refluxing left hydronephrosis and left hydroureter were diagnosed by renal investigations. To the best of our knowledge the association of the described malformations has never been previously reported. The clinical and nosological significance of this new entity is discussed.
We report an inbred Arab family from the United Arab Emirates with two children affected with mental retardation, iris coloboma, optic atrophy, nystagmus, and a distinctive facial appearance. This includes a long narrow face, downslanting palpebral fissures, a narrow nose with hypoplasia of the alae nasi, a small philtrum and a thin upper lip. We suggest that the combination of abnormalities in these children represents a previously undescribed autosomal recessive syndrome.
We report a Brazilian boy, born to normal and nonconsanguineous parents showing, among other signs, brachycephaly, a wide forehead, a widow's peak, hypertelorism, wide palpebral fissures with multiple eyelid colobomas, a broad nasal root, a long philtrum, macrostomia, prominent lips, a high arched palate, a midline alveolar cleft, a small and grooved chin, ear anomalies, structural anomaly of the corpus callosum, and mental retardation. To our knowledge this additional patient defines a particular clinical condition previously reported [Guion-Almeida M.L. Richieri-Costa A. (1999) Clinical Dysmorphol 8;1-4; Masuno M. et al. (2000) Clin Dysmorphol 9:59-60].
The association of moderate mental retardation, behavioural problems, macrocephaly, dysmorphic features with iris coloboma, and supernumerary nipples was observed in two brothers with a terminal deletion 4q33-->4qter and a terminal duplication 7q34-->7qter. The aberration was detected by subtelomere FISH screening and (probably) resulted from a cryptic familial translocation (4;7)(q33;q34).
Loose anagen hair syndrome is an uncommon congenital disorder. It may occur in association with other syndromes and dysmorphic features. We report a girl who fulfilled the diagnostic criteria for this syndrome as proposed by Tosti (Arch Dermatol 2002, 138: 521-522). She also had several other anomalies including colobomas. We suggest that the combination of features in this patient may constitute a specific syndromic phenotype.
In humans, PAX2 haploinsufficiency causes renal-coloboma syndrome (RCS) involving eye abnormalities, renal hypoplasia, and renal failure in early life. The authors previously showed that heterozygous mutant Pax2 mice have smaller kidneys with fewer nephrons, associated with elevated apoptosis in the ureteric bud (UB). However, PAX2 may have a variety of developmental functions such as effects on cell fate and differentiation. To determine whether apoptosis alone is sufficient to cause a UB branching deficit, the authors targeted a pro-apoptotic gene (Baxalpha) to the embryonic kidney under the control of human PAX2 regulatory elements. The exogenous PAX2 promoter directed Baxalpha gene expression specifically to the developing kidney UB, eye, and mid/hindbrain. At E15.5 PAX2Promoter-Baxalpha fetal mice exhibited renal hypoplasia, elevated UB apoptosis, and retinal defects, mimicking the phenotype observed in RCS. The kidneys of E15.5 PAX2Promoter-Baxalpha fetal mice were 55% smaller than those of wild-type fetal mice, and they contained 70% of the normal level of UB branching. The data indicate that loss of Pax2 anti-apoptotic activity is sufficient to account for the reduced UB branching observed in RCS and suggest that elevated UB apoptosis may be a key process responsible for renal hypoplasia. The authors propose a morphogenic unit model in which cell survival influences the rate of UB branching and determines final nephron endowment.
In renal-coloboma syndrome (RCS), null mutations of the PAX2 gene cause renal hypoplasia due to a congenital deficit of nephrons; affected individuals may develop renal insufficiency in childhood. During normal kidney development, PAX2, is expressed at high levels throughout the arborizing ureteric bud (UB); recent observations suggest that one of its key roles is to suppress apoptosis in this collecting duct lineage. The authors hypothesized that increased UB cell apoptosis due to PAX2 haploinsufficiency must directly influence the rate of branching morphogenesis in developing kidney and the number of nephrons that can be formed before birth, when nephrogenesis in humans comes to an end. If so, the authors reasoned that caspase inhibitors might be used to suppress unwanted UB cell apoptosis during kidney development in Pax2(1Neu) mutant mice and rescue the genetic UB branching defect. E17.5 kidneys from Pax2(1Neu) mutant mice had smaller (-25%) longitudinal cross-sectional area and 3.5-fold increase in collecting duct cell apoptosis versus wild-type littermates; mutant E13.5 kidney explants allowed to arborize for 50 h in vitro had 18% fewer terminal branches than wild-types. However, exposure to the caspase inhibitor, Z-VAD-fmk (25 micro M), significantly increased terminal branch number in mutant explants (23%). It also increased branching in wild-type explants, apparently reflecting an effect of Z-VAD-fmk on basal apoptosis induced by ex vivo culture conditions. Similarly, when pregnant mice were injected daily with Z-VAD-fmk (10 micro g/g weight from E10.5 to E17.5), apoptosis of Pax2(1Neu) fetal collecting duct cells was suppressed to 40% of untreated mutants; by E14, terminal branch number was increased to 152% that of untreated litters. These studies support the hypothesis that PAX2 normally optimizes the rate of branching morphogenesis in fetal kidney by suppressing UB apoptosis. Furthermore, it suggests that caspase inhibitors can rescue the branching defect caused by PAX2 mutations.
Incontinentia Pigmenti Achromians is a neurocutaneous disorder of uncertain etiology that has been associated with other systemic manifestations including ophthalmologic, musculoskeletal, neurologic and dental abnormalities. Chromosome abnormalities have been documented in some cases but may be coincidental. We describe a 16-month-old black female with an iris coloboma and single central deciduous maxillary incisor in addition to the hypopigmented skin lesions of hypomelanosis of Ito. The combination has not been previously described.
An autosomal dominant dysplasia-malformation syndrome affecting seven individuals in one family is reported. The components of the syndrome include congenital nasopalpebral lipoma, telecanthus, and bilateral colobomas of upper and lower lids without midface hypoplasia. It appears to be the second recorded example resulting from an autosomal dominant gene fully penetrant in both sexes.
We present two cases of loose anagen syndrome associated with ocular coloboma in two siblings of unaffected parents and with no family history. We believe they represent a new familial association between these two conditions.
We report a 21-month-old girl with symptoms consistent with the Zunich neuroectodermal syndrome, an apparently rare condition first described in 1983. Common features of all previously reported patients as well as in this child are characteristic craniofacial dysmorphism, bilateral colobomas of the retina, sparse and fine hair, hearing loss, ichthyosiform erythroderma, mental retardation, ear anomalies, brachydactyly, and broad second toes. Light microscopic and ultrastructural investigations of the affected skin showed characteristic but nonspecific changes. The structural hair shaft abnormalities as well as the dysplastic nails in our patient have not been described before and are consistent with the previous assumption of an ectodermal dysplasia syndrome.
White sponge naevus occurred in association with coloboma of the iris in six members of one family, across three generations. The association of these two dominantly inherited conditions has not to our knowledge previously been described.
AIM: To describe lesions resembling optic disc duplication and highlight their unusual visual fields. The authors also report the first case of pseudo-duplication of the optic disc with overlying retinal nerve fibre layer. METHODS: Retrospective, non-comparative review of case notes. Humphrey visual fields and OCT-3 imaging were performed. RESULTS: All 11 cases represented peripapillary chorioretinal coloboma, some of which lie superior to the optic disc. A double blind spot or superior hemifield defects can be demonstrated by automated visual field testing. CONCLUSION: Clinical examination and identification of bridging retinal vessels from the true optic disc to the second pseudo disc can usually avoid unnecessary invasive and non-invasive investigations.
A new syndrome characterized by cleft palate, coloboma, hypospadias, deafness, short stature, and radial synostosis has been described. The family history suggests either an autosomal dominant mode of inheritance with limited expression in females or X-linkage. Other syndromes with similar phenotypes and modes of inheritance are discussed. The need for accurate and complete family histories in cases involving cleft palate and cleft lip/palate is discussed in relation to genetic counselling and recurrent risk estimates.