Nance–Horan syndrome

X-linked dominant

Nance–Horan syndrome (NHS) is a rare genetic disorder characterized by congenital cataracts, dental anomalies, and distinctive facial features. It is an X-linked recessive condition, meaning it primarily affects males, while females are typically carriers and may exhibit milder symptoms.

Clinical Features

Individuals with Nance–Horan syndrome often present with:

• Congenital cataracts: Clouding of the lens of the eye present at birth, leading to visual impairment.
• Microcornea: Abnormally small cornea.
• Dental anomalies: Including screwdriver-shaped incisors, supernumerary teeth, and delayed dental eruption.
• Facial dysmorphism: Features such as a long face, large anteverted ears, and a broad nasal bridge.
• Intellectual disability: Varying degrees of cognitive impairment are observed in some individuals.

Genetics

Nance–Horan syndrome is caused by mutations in the NHS gene located on the X chromosome. The NHS gene is responsible for encoding a protein involved in the development of the eyes, teeth, and brain. Due to its X-linked recessive inheritance pattern, males with a single mutated copy of the gene exhibit the full spectrum of symptoms, while females with one mutated copy are typically carriers and may show milder manifestations.

Diagnosis

Diagnosis of Nance–Horan syndrome is based on clinical evaluation, family history, and genetic testing to identify mutations in the NHS gene. Prenatal diagnosis is possible if there is a known family history of the disorder.

Management

Management of Nance–Horan syndrome is symptomatic and supportive, including:

• Surgical intervention for cataracts to improve vision.
• Regular dental care to address dental anomalies.
• Educational support and therapies for individuals with intellectual disabilities.

Epidemiology

Nance–Horan syndrome is a rare disorder, with its exact prevalence unknown. It has been reported in various populations worldwide.

History

The syndrome was first described by Walter E. Nance and Mary Horan in 1974, who identified the characteristic features and inheritance pattern of the disorder.

See Also

• Congenital cataracts
• X-linked recessive inheritance
• Genetic disorders
• Intellectual disability

Related Pages

• NHS gene
• Cataract
• X-linked recessive inheritance
• Genetic counseling