Nance–Horan syndrome, also known as

X-linked Sex linkage describes the sex-specific patterns of inheritance and expression when a gene is present on a sex chromosome (allosome) rather than a non-sex chromosome ( autosome). Genes situated on the X-chromosome are thus termed X-linked, and ...

congenital 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 dev ...

cataract A cataract is a cloudy area in the lens (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...

s and micro

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

, X-linked cataract–dental syndrome, cataracts-oto-dental syndrome, cataract–dental syndrome, and mesiodens–cataract syndrome, is a rare

syndrome characterized by eye and teeth abnormalities,

intellectual disability Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...

, and facial deformities.

Signs and symptoms

The main ocular sign of Nance–Horan syndrome is a congenital nuclear cataract which results in reduced

visual acuity Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye ...

. Other ocular features include

microphthalmia Microphthalmia (Greek: , ), also referred as microphthalmos, is a developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eyes are abnormally small and have anatomic malformations. Microphthalm ...

, microcornea,

strabismus Strabismus is an eye disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at an object can alternate. The condition may be present occasionally or constantly. If present during a ...

, and

nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) Eye movement (sensory), eye movement. People can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in visual impairment, re ...

. Dental features include tapered premolar/molar cusps,

supernumerary teeth Hyperdontia is the condition of having supernumerary teeth, or teeth that appear in addition to the regular number of teeth (32 in the average adult). They can appear in any area of the dental arch and can affect any dental organ. The opposite ...

, screwdriver-shaped

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

, and

diastema A diastema (: diastemata, from Greek , 'space') is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to ...

. Abnormal facial features include anteverted

pinnae Pinna may refer to: Biology * Pinna (anatomy), or auricle, the outer part of the ear * ''Pinna'' (bivalve), a genus of molluscs * Pinna (botany), a primary segment of a compound leaf People Surname * Christophe Pinna (born 1968), French marti ...

, prominent and bulbous nose, and long narrow face. 30% of males with Nance–Horan syndrome have

intellectual disabilities Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...

. Carrier females exhibit less severe clinical symptoms, including lens opacities at the posterior Y-sutures with minimal or no loss of vision, modest face dysmorphism, and dental abnormalities.

Genetics

This syndrome is caused by

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

s in the Nance Horan gene (

NHS The National Health Service (NHS) is the term for the publicly funded health care, publicly funded healthcare systems of the United Kingdom: the National Health Service (England), NHS Scotland, NHS Wales, and Health and Social Care (Northern ...

) which is located on the short arm of the

X chromosome The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its u ...

(Xp22.13).

Diagnosis

Management

There is no known cure for this syndrome. Patients usually need ophthalmic surgery and may also need dental surgery. Genetic counseling and screening of the mother's relatives is recommended.

History

This syndrome was first described by Margaret B. Horan and Walter Elmore Nance in 1974.

References

External links

{{DEFAULTSORT:Nance-Horan syndrome Blindness Disorders of lens Rare genetic syndromes Congenital disorders of eyes Syndromes affecting teeth Syndromes affecting the eye Syndromes with craniofacial abnormalities