Nance–Horan syndrome

Nance–Horan syndrome
Other names	Cataract X-linked with Hutchinsonian teeth
This condition is inherited in an X-linked dominant manner.
Specialty	Ophthalmology

Nance–Horan syndrome is a rare X-linked dominant syndrome characterized by congenital cataracts leading to profound vision loss, characteristic dysmorphic features, and dental anomalies.^[1][2] Microcornea, microphthalmia, and mild or moderate intellectual disability may accompany these features. Heterozygous females often manifest similarly but with less severe features than affected males.

Dental features:^[2]

• small teeth in males
• pointed (screwdriver shaped or conical) incisors (sometimes called Hutchinson teeth)
• incisors with an irregular incisal edge
• canines: enlarged and globular; may be dome or bud shaped with trilobed edge
• premolars and molars: small, round and globular; may have supernumary lobes (mulberry or lotus flower shape)
• widely separated teeth (diastemma)
• hypoplastic enamel
• dental agenesis
• presence of mesiodents (median incisor behind normal upper incisors)
• pulp chamber anomalies

Facial features:^[2]

• anteverted pinnae
• long face
• prominent nasal bridge and nose
• prognathism occasionally

Ophthalmic features:^{[citation needed]}

• bilateral congenital nuclear opacities (100%)
• severe amblyopia
• nystagmus (93%)
• strabismus (43%)
• microcornea (96%)
• congenital glaucoma
• scleral staphylomas
• retinal cystoid degeneration
• microphthalmia

These lead to severe visual impairment in affected males.

Other:^[2]

• The fourth metacarpal may be shortened

30% of patients also have some degree of intellectual impairment: of these 80% are mildly to moderately affected: the other 20% may have developmental delays and behavior problems.^{[citation needed]}

Carrier females display milder variable symptoms of disease. Ocular signs are present in 90% of heterozygous females. These are typically lens opacities often involving the posterior Y sutures. More rarely dental anomalies and the characteristic facial features may also occur.^{[citation needed]}

This syndrome is caused by mutations in the Nance Horan gene (NHS) which is located on the short arm of the X chromosome (Xp22.13).^[3]

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.^{[citation needed]}

This syndrome was first described by Margaret B. Horan and Walter Elmore Nance in 1974.^[4][5]