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Nance-Horan syndrome
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Unknown prevalence. Mutations of the NHS gene (Xp22.2) cause a truncated protein. The differential expression of two isoforms, NHS-A and NHS-1A, differently localized in the cell, may in part explain the variable clinical manifestations. Heterozygous women present with an attenuated, usually subclinical, phenotype.
The clinical manifestations are:
- eye involvement: congenital bilateral cataract (100% of the cases), generally severe, dense and often total and microcornea (96% of cases), or even a microphthalmos. The eye involvement results in 93% of cases in a severely impaired vision as evidenced by the existence of nystagmus (93%), sometimes associated with strabismus (43%).
- dental abnormalities, almost always present, affecting deciduous as well as permanent teeth; they have a very high value diagnostic value, although they are easily overlooked. The most frequent are diastema, supernumerary molar and incisors - frequently impacted, abnormalities of shape ('screwdriver-shaped' teeth).
- facial dysmorphism, frequent, which may include: a elongated face; prognathism; large nose, with a prominent nasal root; bat ears which are also very large.
- intellectual deficit in about 30% of cases, with inter- and intra-family variability. This deficit is mild or moderate (80%), without associated motor retardation, except in 20% of cases where it is severe/profound and associated with autism signs.
Anesthetic implications:
impaired sight (see cataract), fragile teeth, prognathism
References :
- Ding X, Patel M, Herzlich AA, Sieving PC, Chan C-C.
Ophthalmic pathology of Nance-Horan syndrome: case report and review of the literature.
Ophthalmic Genetics, 2009; 30: 127-35.
Updated: May 2017