00:01
So let's think more closely about
congenital muscular dystrophies
and congenital myopathies and
really focused on understanding
the similarities and differences between
these two causes of neonatal hypotonia.
00:13
The congenital muscular
dystrophies are muscle dystrophies.
00:17
So there is a degeneration of the
muscle that's present at/around birth.
00:23
Congenital muscular
dystrophies are different
from the other muscular dystrophies
because they begin at birth.
00:28
Duchenne's,
Becker's, Limb-girdle
and the other muscular dystrophies
that we've learned about
present much later in life,
in childhood or adolescence
or even in adulthood.
00:37
And that's different from
congenital muscular dystrophies.
00:41
They have a genetic cause,
we're going to learn that the
congenital muscular dystrophies
are from similar
proteins involved
in the dystrophin glycoprotein
complex that anchors the muscle
to the extracellular matrix.
00:52
There is a
degenerative etiology.
00:54
The muscle is degenerating and
slowly dying and necrosing over time
and so these conditions
follow a progressive course.
01:01
The baby begins
with some strength
and slowly becomes a hypotonic
and weaker and weaker over time
and ultimately, many patients die
from congenital muscular dystrophies.
01:12
In contrast, we see that congenital
myopathies are also muscle disorders
that are present at/around
the time of birth.
01:19
These are different from the acquired
myopathies that present in adulthood
and are seen at
the time of birth.
01:25
There is also a genetic cause.
01:28
But here patients
follow a static course
or very slowly progressive
course over time.
01:33
There's not degeneration
of the muscle
or necrosis of the muscle
or dying of the muscle.
01:37
The muscle just doesn't work
because of the accumulation of
certain proteins or byproducts
or abnormal contents.
01:45
And this results in a dysfunctional
muscle that does not degenerate over time.
01:51
Let's walk through
each of these,
the congenital muscular dystrophies
and the congenital myopathies.
01:55
And first we'll focus on
congenital muscular dystrophies.
01:58
There are five that I
want you to be aware of.
02:01
The first is Merosin-deficient
congenital muscular dystrophy,
Fukuyama disease,
Muscle-eye-brain desease,
Walker-Warburg and Ullrich
congenital muscular dystrophy.
02:13
All of these are congenital
muscular dystrophies,
they present with
a hypotonic infant.
02:18
Patients have a progressive weakness over
time, there's degeneration of the muscle
and I want you to
know the five names
but not be invested into all the
details of each individual condition.
02:29
With the other muscular
dystrophies we talked about,
abnormalities in the dystrophin
glycoprotein complex.
02:36
This is that protein
complex that sits
in the cell membrane of the
muscle, the sarcolemma.
02:41
It anchors the extracellular
matrix to the internal muscle.
02:45
In this docking, this
infrastructure, this side of skeleton
that anchors the muscle in this way is
critical for normal muscle function,
loss of any of the proteins that
are involved in this scaffolding
results in a muscular dystrophy,
degeneration of the muscle and
varying degrees of inflammation.
03:02
With the congenital
muscular dystrophies,
we see abnormalities in a
number of associated proteins.
03:08
Fukutin, POMT1 and a number
of different proteins
that are involved in these conditions,
the congenital muscular dystrophies
and different from the
other muscular dystrophies,
like Duchenne,
Becker's and limb-girdle.
03:22
Let's think about some
of the features of these
individual congenital
muscular dystrophies.
03:26
And we'll start first with
muscle-eye-brain disease.
03:29
The abnormality is with a gene in
the POMGnT1, as you can see here
and that's something we can
test for on genetic testing.
03:38
We'll look for
mutations in that gene.
03:41
The clinical presentation
with muscle-eye-brain disease
includes severe muscle weakness,
often with mental
retardation epilepsy,
patients can have neuronal migration
disorders and ocular abnormalities
and that complex points us
to muscle-eye-brain disease.
03:55
When we see patients with severe
hypotonia, mental retardation, epilepsy,
we'll consider genetic testing
to evaluate for this condition.
04:03
What about Fukuyama disease?
This is a problem with the Fukutin
protein that we saw on the last slide.
04:09
Patients again present with severe
proximal and axial muscle weakness,
floppy baby, mental
retardation, epilepsy,
again, neuronal migration disorders
and ocular abnormalities can be seen.
04:21
And so you can see the similarities
in these two presentations
and the importance of
genetic testing to screen
for the individual genetic event
that's giving rise to the disease.
04:30
Walker-Warburg is another one
of these conditions again,
abnormality and a similar gene
to the muscle-eye-brain
disease but a different area.
04:39
We see clinical features
including severe muscle weakness,
death in infancy this
can be quite severe,
absent psychomotor development,
neuronal migration disorder
and abnormalities and
ocular abnormalities.
04:50
And then there are several other
again congenital muscular dystrophies
that can present with varying
degrees of muscle weakness
and other conditions and
genetic testing is critical
for evaluating the
precise diagnosis.
05:05
What about the
congenital myopathies?
Again, these presented infancy just
like congenital muscular dystrophies.
05:11
But they are myopathy,
a muscle disorder
that results from dysfunction of the
muscle but not degeneration over time.
05:20
And there are four conditions,
names that I'd like for you to know.
05:23
Nemaline-rod myopathy,
centronuclear myopathy,
central core myopathy,
and myofibrillar myopathy.
05:33
The key things to know about these
conditions they're congenital,
they begin at the time or
around the time of birth,
can present with a very weak
hypotonic infant with difficulty
with feeding and sucking
and insignificant motor weakness and loss
of motor or absence of motor milestones.
05:50
They are static over time.
05:52
So there is dysfunction of the muscle, the
muscle doesn't work and patients are weak,
but that weakness really more stable
are very slowly progressive over time
which is different from the
congenital muscular dystrophies.
06:04
There are structural abnormalities
that occur in the muscle
that build up in the
cell, in the muscle cell
and result in inclusions.
06:12
And those inclusions are
what we see on histopathology
and give each of these
four conditions their name.
06:18
With central core myopathy,
we see a central core
that's that white area that
you see on the histology,
and that tips us off
with a muscle biopsy
that we're dealing with
central core myopathy.
06:28
Centronuclear myopathy,
here we can see this
abnormal nuclear content
within the muscle.
06:33
Nemaline-rod myopathy
has this protein build up
within the muscle
that we see on this
gomori trichrome stain which is a very
characteristic stain to show this problem.
06:44
And then myofibrillar myopathy, we see these
fibilliar contents within the muscle.
06:48
And again, we don't need to know all
the details of each of these conditions
but that they're evaluated and
diagnosed really histopathologically
based on these findings present
within a hypotonic infant
with a static course over time.
07:00
And treatment for nearly
all of these conditions,
congenital muscular dystrophies
and congenital myopathies
is primarily supportive.