Nance Horan (cataract dental) Syndrome
What is Nance-Horan Syndrome (NHS)?
Nance Horan syndrome is a rare cause of cataracts in
children – most children with cataracts do not have Nance
Horan syndrome but there are thought to be a few children with
cataracts who have this condition who are only mildly affected
by it, and therefore have not had a diagnosis. This is a brief
overview of Nance Horan syndrome written by Miss Isabelle
Russell-Eggitt in response to a number of parents on the CCN
email group who had noticed that their child with cataracts had
unusual problems with their teeth:
“Nance-Horan Syndrome is a genetic disorder inherited
through the female line in a family. A father cannot pass this
type of cataract on to his son. This disorder is only passed on
by a mother to her sons and daughters with a 50% chance that
each will have the condition themselves.
Congenital cataract is a main feature, but expression of the
gene varies widely between individuals with many girls and
mothers having no obvious eye problem and most boys having
dense cataracts and slightly small eyes. Some boys may be more
mildly affected having only a minimal cataract in one eye and
some girls may have a dense cataract in one eye.
This disorder is often not diagnosed and a label of
‘congenital cataract’ or ‘inherited
cataract’ is given. This is due to a combination of lack
of awareness of this disorder even amongst paediatric
ophthalmologists and that many children have a milder condition
than the classic textbook case. It is helpful for the family
and specialists to have the correct diagnosis so that the other
features do not go undetected and the child receives the best
possible care.
The eye of an affected individual not only has a cataract
but often in a male is slightly small making them a less likely
candidate for an intraocular lens early in life. Surgery may be
more difficult with a higher risk of bleeding inside the eye
during the procedure and a higher risk of glaucoma. The optic
disc may look slightly unusual and in some cases the
‘cup’ in the disc may be thought to be due to
glaucoma when the eye pressure is normal and this is just the
way the disc developed. Many individuals with NHS do achieve
good vision yet some in spite of the best possible care do have
complications and a poor outcome.
Nance-Horan also affects the development of teeth. As with
the eyes the teeth may be totally normal in some family members
who have the NHS gene and in others the teeth have an abnormal
shape and poor enamel and are therefore very prone to
caries.
Many individuals with the NHS gene thrive at school, but
some do have behavioural or learning difficulties that in a few
cases may be severe.
The name of the disorder comes from the names of 2 doctors,
Nance and Horan who independently first described cases in the
medical literature. The gene which is defective is now known
but testing for defects in this gene is not yet available at
one of the UK reference laboratories. Occasionally a gene test
may be offered by one of the centres doing research into the
‘cataract genes’, but pre-natal diagnosis is not at
present available. The diagnosis is usually made on features
especially on the milder cataract type seen in some girls in
the family and on the teeth shape. The shape of the external
ears may also be suggestive of NHS, being often slightly cup
shaped and prominent.”
If you feel that your child with cataracts may be affected
by Nance Horan syndrome, your child's ophthalmologist or GP
should be able to refer your child to a paediatrician.
Checked for medical accuracy by Miss Isabelle
Russell-Eggitt, Consultant Paediatric Ophthalmologist, Great
Ormond Street Hospital, London
Last updated: 15/01/09
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Childhood Cataract Network
