The
Bardet-Biedl and Laurence-Moon syndromes are two uncommon disorders.
Both syndromes are genetic, that is, caused by altered genes,
and occur throughout the world, equally in men and in women.
Historically these conditions were so similar that for some
time they had been considered the same disorder.
However, in the past few years, it has become apparent that
these are two separate and distinct syndromes.
In
1866 doctors Laurence and Moon in England described four members of
the same family who had retinal problems, unsteady gait and spinal
cord problems, and developmental delays.
In the 1920’s Doctors Bardet (in France) and Biedl (in
Germany) independently published articles describing patients with
extra fingers and toes at birth, infantile obesity, and retinal
disorders.
The similarities of the signs in these patients were so
striking that it was decided to adopt the suggestion to speak of these
as one syndrome: Laurence-Moon/Bardet-Biedl Syndrome.
Recently,
however, physicians again tend to separate the Laurence-Moon and
Bardet-Biedl Syndromes.
Although they share some common features, many features are
distinct to either one or the other condition.
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How common are
these conditions ?
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It
is difficult to give exact numbers about the frequency of each
syndrome. Based on a
Swiss study several decades ago, Bardet-Biedl Syndrome was estimated
to occur in 1 of 160,000 births in European countries. In other parts of the world, this estimate may differ
greatly. For example, in
Middle East these numbers are far higher (in Kuwait BBS is estimated
to occur in about one person in 35,000).
From these estimates, we expect that only one or two children
are born in the Netherlands each year with Bardet-Biedl Syndrome.
The
estimates for Laurence-Moon Syndrome are much lower still.
In Kuwait, the frequency of this syndrome was also estimated at
1 in 210,000 births. No
reliable figures about the occurrence of Laurence-Moon Syndrome in the
Netherlands are available.
| Laurence-Moon en
Bardet-Biedl
Syndromes |
| *
Congenitial obesity |
| *
Retinal abnormalities |
| *
Hypogonadism |
| *
Learning disabilities |
| Laurence-Moon
Syndrome |
| *
Spasticity (often progressive) or ataxia |
| * No
skeletal deformities of hands and feet |
| Bardet-Biedl
Syndrome |
| *
Hand and foot anomalies in about 90% of children,especially
extra fingers and/or toes |
| *
Kidney disorders in approximality 75-95% of children |
| *
Almost never spasticity |
Features
in each disorder are often not obvious initially, which may therefore
delay diagnosis. Extra
fingers and/or toes (polydactyly) are apparent at birth but are not
always present. Of
course, polydactyly can also occur by itself, without any association
with a syndrome. Retinal
disorders are almost always present, both in Laurence-Moon and in
Bardet-Biedl Syndromes. However,
usually problems with vision are not noticed until the ages 4 to 6
years or even later. Other
features of these syndromes are often so subtle as to go unnoticed or
unattended, such as the weight gain and obesity.
Another
concern is that these signs do not occur in every affected individual.
The variations in these disorders are wide, not only among
affected children from different families, but even among affected
children in the same family.
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