Question: What is (are) Nance-Horan syndrome ?
Answer: Nance-Horan syndrome is a rare genetic disorder that may be evident at birth. It is characterized by teeth abnormalities and cataracts, resulting in poor vision. Additional eye abnormalities are also often present, including a very small cornea and nystagmus. In some cases, the condition may also be associated with physical abnormalities and/or intellectual disability. The range and severity of symptoms may vary greatly from one person to another, even among affected members of the same family. Nance-Horan syndrome is caused by a mutation in the NHS gene and is inherited as an X-linked dominant trait, which means that both males and females can be affected, but males often have more severe symptoms.The treatment is directed toward the specific symptoms that are apparent in the individual.
Source: GARD

Question: What are the symptoms of Nance-Horan syndrome ?
Answer: What are the signs and symptoms of Nance-Horan syndrome? The main features of Nance-Horan syndrome include congenital cataracts, dental abnormalities, distinctive facial features, and in some cases, intellectual disability. In affected males, the primary physical characteristic is the presence of dense clouding of the lens (cornea) of both eyes at birth (congenital bilateral cataracts). The cataracts usually result in blurred vision and severely decreased clearness or clarity of vision (visual acuity). Vision loss can potentially be profound. Males with Nance-Horan syndrome may have additional eye abnormalities, including a very small cornea (microcornea); involuntary movements of the eyes (nystagmus), and/or misalignment of the eyes (strabismus). In some cases, the entire eye may be abnormally small (microphthalmia) and/or the upper eyelid may droop (ptosis). Males with Nance-Horan syndrome may also have several dental abnormalities such as unusually shaped, extra (supernumerary) teeth, absence of some teeth (dental agenesis), impacted teeth or unusually wide spaces (diastema) between some of the teeth. The front teeth, or incisors, are usually tapered and 'screwdriver-shaped'. The teeth in the back of the mouth may be cone-shaped, rounded, or cylindrical. In many males with Nance-Horan syndrome, other physical findings may also occur. Distinctive facial features may be present, but may be subtle. The ears may be flared forward and unusually prominent. Affected males may also have a large, prominent nose with a high, narrow nasal bridge, a narrow prominent jaw, and sometimes a long, narrow face. Some males with Nance-Horan syndrome may also experience delays the skills necessary for coordinating muscular and mental activity. In addition, some reports suggest that approximately 20 to 30 percent of affected males may have varying levels of intellectual disability, which is usually mild to moderate; but in some cases can be severe. Females who carry a single copy of the mutation in the NHS gene may develop some symptoms of the disorder. However, symptoms are usually milder and more variable than those seen in males. Affected females may have abnormally small corneas (microcornea) and/or some clouding of the cornea. Vision may be normal, or there may be slightly decreased visual acuity. Without appropriate treatment, clouding of the cornea can lead to total cataracts later in life. Females often have some dental abnormalities, such as abnormally-shaped front teeth and/or unusually wide spaces between some of the teeth. Affected females usually do not develop intellectual disability. The Human Phenotype Ontology provides the following list of signs and symptoms for Nance-Horan syndrome. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormal nasal morphology 90% Cataract 90% Long face 90% Mandibular prognathia 90% Microcornea 90% Nystagmus 90% Prominent nasal bridge 90% Visual impairment 90% Intellectual disability, moderate 80% Abnormality of the metacarpal bones 50% Cognitive impairment 50% Increased number of teeth 50% Strabismus 50% Aplasia/Hypoplasia affecting the eye 7.5% Behavioral abnormality 7.5% Glaucoma 7.5% Retinal detachment 7.5% Autism - Broad finger - Congenital cataract - Diastema - Macrotia - Microphthalmia - Narrow face - Posterior Y-sutural cataract - Prominent nose - Screwdriver-shaped incisors - Short phalanx of finger - Supernumerary maxillary incisor - Visual loss - X-linked dominant inheritance - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD

Question: What causes Nance-Horan syndrome ?
Answer: What causes Nance-Horan syndrome? Nance-Horan syndrome is caused by a mutation in the NHS gene, which is located on the X chromosome. Some patients have losses (deletions) of part of the chromosome X short arm (p) within the region involving the NHS gene and other genes that are located in this region. These patients may have more problems and the problems may be more serious.
Source: GARD

Question: Is Nance-Horan syndrome inherited ?
Answer: How is Nance-Horan syndrome inherited? Nance-Horan syndrome is inherited as an X-linked dominant trait. In X-linked dominant inheritance, both males and females can be affected by a condition. However, affected males tend to have more severe features than females. X-linked conditions result from mutations of a gene located on an X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. In females, disease traits resulting from the abnormal copy of a gene on one X chromosome can be 'masked' by the normal copy of the gene on the other X chromosome. Because only one functioning X chromosome is required in males and females, one of the X chromosomes in each cell of a female is essentially 'turned off,' usually in a random pattern (X chromosome inactivation). Therefore, if the X chromosome with the gene mutation is activated in some cells, female carriers may have some mild features of the disorder. However, since males only have one X chromosome, they will likely fully express a condition if they inherit a gene mutation that is located on the X chromosome.
Source: GARD