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Microspherophakia
Microspherophakia is a rare congenital autosomal recessive condition where the lens of the eye is smaller than normal and spherically shaped. This condition may be associated with a number of disorders including Peter's anomaly, Marfan syndrome, and Weill–Marchesani syndrome. The spherical shape is caused by an underdeveloped zonule of Zinn, which doesn't exert enough force on the lens to make it form the usual oval shape. It is a result of a homozygous mutation to the LTBP2 gene. See also * Ectopia lentis References Further readingMicrospherophakia at Online Mendelian Inheritance in Man
Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of human ...
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Weill–Marchesani Syndrome
Weill–Marchesani syndrome is a rare genetic disorder characterized by short stature; an unusually short, broad head (brachycephaly) and other facial abnormalities; hand defects, including unusually short fingers (brachydactyly); and distinctive eye (ocular) abnormalities. It was named after ophthalmologists Georges Weill (1866–1952) and Oswald Marchesani (1900–1952) who first described it in 1932 and 1939, respectively. The eye manifestations typically include unusually small, round lenses of the eyes (microspherophakia), which may be prone to dislocating (ectopia lentis), as well as other ocular defects. Due to such abnormalities, affected individuals may have varying degrees of visual impairment, ranging from nearsightedness myopia to blindness. Weill–Marchesani syndrome may have autosomal recessive inheritance involving the ''ADAMTS10'' gene, or autosomal dominant inheritance involving the ''FBN1'' gene. In some cases there is no association with either of these genes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Congenital Disorder
A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or developmental disability, developmental. The disabilities can range from mild to severe. Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and functional disorders in which problems exist with how a body part works. Functional disorders include metabolic disorder, metabolic and degenerative disease, degenerative disorders. Some birth defects include both structural and functional disorders. Birth defects may result from genetic disorder, genetic or chromosome abnormality, chromosomal disorders, exposure to certain medications or chemicals, or certain vertically transmitted infection, infections during pregnancy. Risk factors include folate deficiency, alcohol drink, d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recessive
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second is called recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new (''de novo'') or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes ( autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child (see Sex linkage). Since there is only one Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance, such as incompl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lens (anatomy)
The lens, or crystalline lens, is a Transparency and translucency, transparent Biconvex lens, biconvex structure in most land vertebrate eyes. Relatively long, thin fiber cells make up the majority of the lens. These cells vary in architecture and are arranged in concentric layers. New layers of cells are recruited from a thin epithelium at the front of the lens, just below the basement membrane surrounding the lens. As a result the vertebrate lens grows throughout life. The surrounding lens membrane referred to as the lens capsule also grows in a systematic way, ensuring the lens maintains an optically suitable shape in concert with the underlying fiber cells. Thousands of suspensory ligaments are embedded into the capsule at its largest diameter which suspend the lens within the eye. Most of these lens structures are derived from the epithelium of the embryo before birth. Along with the cornea, aqueous humour, aqueous, and vitreous humours, the lens Refraction, refracts light, Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anterior Segment Mesenchymal Dysgenesis
Anterior segment mesenchymal dysgenesis, or simply anterior segment dysgenesis, is a failure of the normal development of the tissues of the anterior segment of the eye. It leads to anomalies in the structure of the mature anterior segment, associated with an increased risk of glaucoma and corneal opacity. Peters' (frequently misspelled as Peter's) anomaly is a specific type of mesenchymal anterior segment dysgenesis, in which there is central corneal leukoma, adhesions of the iris and cornea and abnormalities of the posterior corneal stroma, Descemet's membrane, corneal endothelium, lens and anterior chamber. Pathophysiology Several gene mutations have been identified underlying these anomalies, with the majority of anterior segment dysgenesis genes encoding transcriptional regulators. In this review, the role of the anterior segment dysgenesis genes ''PITX2'' and ''FOXC1'' is considered in relation to the embryology of the anterior segment, the biochemical function of these prot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marfan Syndrome
Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically have hypermobility (joints), exceptionally flexible joints and scoliosis, abnormally curved spines. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. The lungs, eyes, bones, and the dura mater, covering of the spinal cord are also commonly affected. The severity of the symptoms is variable. MFS is caused by a mutation in ''FBN1'', one of the genes that make fibrillin, which results in abnormal connective tissue. It is an autosomal dominant disorder. In about 75% of cases, it is inherited from a parent with the condition, while in about 25% it is a new mutation. Diagnosis is often based on the Ghent criteria, family history and genetic testing (DNA analysis). Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zonule Of Zinn
The zonule of Zinn () (Zinn's membrane, ciliary zonule) (after Johann Gottfried Zinn) is a ring of fibrous strands forming a zonule (little band) that connects the ciliary body with the crystalline lens of the eye. The Zonular fibers are viscoelastic cables, although their component microfibrils are stiff structures. These fibers are sometimes collectively referred to as the suspensory ligaments of the lens, as they act like suspensory ligaments. Development The non-pigmented ciliary epithelial cells of the eye synthesize portions of the zonules. Anatomy The zonule of Zinn is split into two layers: a thin layer, which lies near the hyaloid fossa, and a thicker layer, which is a collection of zonular fibers. Together, the fibers are known as the suspensory ligament of the lens. The zonules are about 1–2 μm in diameter. The zonules attach to the lens capsule 2 mm anterior and 1 mm posterior to the equator, and arise of the ciliary epithelium from the pars plana regi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are diploid. Diploid organisms have the same locus (genetics), loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal Sex-determination system#Chromosomal determination, sex-determination system. If both alleles of a diploid organism are the same, the organism is #Homozygous, homozygous at that locus. If they are different, the organism is #Heterozygous, heterozygous at that locus. If one allele is missing, it is #Hemizygous, hemizygous, and, if both alleles are missing, it is #Nullizygous, nullizygous. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ectopia Lentis
Ectopia lentis is a displacement or malposition of the eye's lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or luxated lens. Ectopia lentis in dogs and cats Although observed in humans and cats, ectopia lentis is most commonly seen in dogs. Ciliary zonules normally hold the lens in place. Abnormal development of these zonules can lead to primary ectopia lentis, usually a bilateral condition. Luxation can also be a secondary condition, caused by trauma, cataract formation (decrease in lens diameter may stretch and break the zonules), or glaucoma (enlargement of the globe stretches the zonules). Steroid administration weakens the zonules and can lead to luxation, as well. Lens luxation in cats can occur secondary to anterior uveitis (inflammation of the inside of the eye). Anterior lens luxation With anterior lens luxation, the lens pushes into the iris or ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Online Mendelian Inheritance In Man
Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of human genes and genetic disorders and traits, with a particular focus on the gene-phenotype relationship. , approximately 9,000 of the over 25,000 entries in OMIM represented phenotypes; the rest represented genes, many of which were related to known phenotypes. Versions and history OMIM is the online continuation of Victor A. McKusick's ''Mendelian Inheritance in Man'' (MIM), which was published in 12 editions between 1966 and 1998.McKusick, V. A. ''Mendelian Inheritance in Man. Catalogs of Autosomal Dominant, Autosomal Recessive and X-Linked Phenotypes.'' Baltimore, MD: Johns Hopkins University Press, 1st ed, 1996; 2nd ed, 1969; 3rd ed, 1971; 4th ed, 1975; 5th ed, 1978; 6th ed, 1983; 7th ed, 1986; 8th ed, 1988; 9th ed, 1990; 10th ed, 1992. Nearly all of the 1,486 entries in the first edition of MIM discussed phenotypes. MIM/OMIM is produced and curated at the Johns Hopkins School of Medicine ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Diseases And Disorders
Genetic may refer to: *Genetics, in biology, the science of genes, heredity, and the variation of organisms **Genetic, used as an adjective, refers to genes ***Genetic disorder, any disorder caused by a genetic mutation, whether inherited or de novo ***Genetic mutation, a change in a gene ****Heredity, genes and their mutations being passed from parents to offspring **Genetic recombination, refers to the recombining of alleles resulting in a new molecule of DNA *Genetic relationship (linguistics), in linguistics, a relationship between two languages with a common ancestor language *Genetic algorithm In computer science and operations research, a genetic algorithm (GA) is a metaheuristic inspired by the process of natural selection that belongs to the larger class of evolutionary algorithms (EA). Genetic algorithms are commonly used to g ..., in computer science, a kind of search technique modeled on evolutionary biology See also * Genetic memory (other) {{disam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rare Diseases
A rare disease is any disease that affects a small percentage of the population. In some parts of the world, the term orphan disease describes a rare disease whose rarity results in little or no funding or research for treatments, without financial incentives from governments or other agencies. Orphan drugs are medications targeting orphan diseases. Most rare diseases are genetic in origin and thus are present throughout the person's entire life, even if symptoms do not immediately appear. Many rare diseases appear early in life, and about 30% of children with rare diseases will die before reaching their fifth birthdays. Fields condition is considered the rarest known disease, affecting three known individuals, two of whom are identical twins. With four diagnosed patients in 27 years, ribose-5-phosphate isomerase deficiency is considered the second rarest. While no single number has been agreed upon for which a disease is considered rare, several efforts have been undertaken ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
