00:01
So focal segmental
glomerulosclerosis,
it's quite a mouthful to say
so we're going to
abbreviate it with FSGS.
00:07
And I want to talk about
why we call it that.
00:10
One of the things I love about this is our
pathologist have come up with this name
and it pathologically describes
exactly what's going on
when we say the word focal
it means that when we do the
biopsy there's less than 50%
of glomeruli that are involved.
00:23
So in the kidney by this
disease process less than 50
or and percent of those glomeruli
are going to be involved.
00:29
And then segmental means that,
when you're looking
at a glomerulus
only a segment of the glomerulus
is involved sclerosis means scar.
00:37
So less than 50% of
glomeruli segmental
are scarred,
sclerosis meaning scar.
00:44
So that's where FSGS comes from.
00:46
It's the most common form of
nephrotic syndrome in adults.
00:50
It's a second most
common in children,
second minimal change disease
that we as we just discussed.
00:56
And again, it accounts for 35%
of all biopsies of nephrotic
syndrome in adults,
there is an increased incidence
in African American people
as well as male gender.
01:08
So when we think about
the ideology behind FSGS,
it's a little bit complicated.
01:12
So we like to talk about
it in terms of primary FSGS
and secondary FSGS.
01:17
Under the primary category,
we think about idiopathic
and remember that's just a word
to say that we haven't yet discovered
what the exact etiology is,
but there's also a genetic and
familial type of FSGS as well.
01:29
And this involves genes that
encode the slit diaphragm proteins
in the foot processes
of the podocyte.
01:33
That includes jeans like
nephron, podocin,
TRPC6 and alpha-acrinin-4.
01:38
There's also an
association with the MYH9
and the APOL1 allelic variants
in the African populations.
01:45
So we talked about
this previously
with causing hypertensive
and chronic hypertension
and chronic kidney disease.
01:51
We can also see a variant
in association with FSGS.
01:56
So there's also
a secondary FSGS,
and this is going to occur
in many forms of renal injury
and systemic diseases.
02:02
It could be due to a
loss of renal mass.
02:05
It could be due to
things like obesity,
HIV which is going to
directly affect the podocyte,
sickle cell disease, which is
really a form of loss of renal mass,
and drugs that directly
into the podocyte.
02:16
This is these are things
like pamidronate and heroin.
02:19
It's going to present more often
with an erotic range proteinuria
rather than nephrotic syndrome.
02:24
So oftentimes people
who have secondary FSGS,
may just show up with
protein in their urine,
but they're not always going
to have the hypoalbuminemia
in the lipid
abnormalities in edema
that we would see
with our patients with
full-blown nephrotic syndrome
as you're going to
see him primary fsgs.
02:41
So when we are
biopsy our patients
what we see on biopsy
on our light microscopy
This is a PAS stain,
we can actually see
segments of Scar.
02:52
So essentially what my arrow
is pointing to over here
is we have a sneaky
attachment to Bowman's capsule
and we have this area of
scar that's accumulated
accumulated in a segment
of the glomerulus
right at about 7 o'clock.
03:06
Am i immunofluorescence?
It's very nonspecific.
03:09
Sometimes we get this innocent
trapping of complements C3
in the area of scar,
but it's not doing
anything pathologically.
03:17
And then on electron microscopy
what we see is in
the capillary loop
that involves the scar,
We have podocyte foot
processes of effacement.
03:25
My arrow is again
pointing over here
to that foot process
being effaced
you can actually see some of
these little foot processes
that are undergoing micro
Villas transformation as well.
03:35
Now, in secondary FSGS,
we're only going to see that
foot processes effacement
over the areas of capillary loop
that are involved by
segmental sclerosis.
03:45
In primary FSGS,
over 50% of those capillary
loops that are not involved
by segmental Scar or going to
have foot process effacement.
03:54
So that's a very helpful clue
in order to distinguish between
primary and secondary FSGS.
04:02
When we think about the
pathogenesis behind FSGS,
in primary,
It's really an injury
to the podocyte
that most likely is due to
some kind of circulating toxin
which is supported
by the rapidity
of recurrent disease
following renal transplant.
04:15
So it's very interesting when you
have a patient with primary FSGS
and you transplant that patient
sometimes within 24 hours
that patient can have an increase
or explosion in proteinuria.
04:26
When you biopsy that patient
they have changes consistent
with minimal change disease
that eventually through
time develops into FSGS.
04:34
So it makes you think that there's
some kind of circulating toxin
that's causing this to happen.
04:39
We do think again, this is most likely
related to minimal change disease
because of what we see
pathologically as they described.
04:46
And again, it's probably on
the same disease continuum,
but people with FSGS
have a much less
or reduced responsiveness to
therapy compared to people
who have minimal change disease.
04:58
In the secondary form of FSGS.
05:00
We have injury to the podocytes
either by hyperfiltration mechanisms
or an increase,
or and an increased in glomerular
capillary hypertension.
05:10
This is going to be
due to those cases
that include reduced renal mass,
patients with chronic kidney
disease, for example,
our patient who has sickle cell
disease will have reduced renal mass.
05:20
We also have hyperfiltration
and glomerular capillary
hypertension in obese patients
particularly morbid obesity
people greater than 40
for their BMI,
tend to have vasodilation
of the efferent arteriole
glomerular capillary
hypertension
and they're at risk of
obesity related FSGS.
05:37
We can also have direct
injury to the podocyte,
and those are things
from viruses like HIV
that directly
affects the podocyte
or drugs like
pamidronate or heroin.
05:50
So in terms of how
patients do overtime
and primary FSGS patients
may present either with acute
onset of nephrotic syndrome,
or it may be a little
bit more insidious.
06:00
Sometimes we can
see some hematuria.
06:03
They typically will
have hypertension
and variable degrees of
reduced renal function.
06:08
Our patients again have no
abnormalities in serum complements,
complement is not
getting activated.
06:14
In secondary FSGS,
our patients always present
with an insidious onset.
06:19
Remember this is something
that's happening slowly over time
and they may not have the full
constitution of nephrotic syndrome.
06:25
They often present with
asymptomatic proteinuria
without the
hypoalbuminemia or edema.
06:31
Untreated, primary FSGS will
follow a progressive course
to end stage renal disease.
06:36
So the rate of
spontaneous remission
in this population is
really less than 10%.
06:42
The risk factors for
progression include have,
include having a high
level of proteinuria,
so greater than 10
grams at presentation
people who have
reduced renal function
meaning that they have
an elevated creatinine
at the time of diagnosis.
06:53
And just as a membranous the presence
of tubulointerstitial fibrosis.
07:00
So when we think about
treatment of primary FSGS,
it's important that all of our patients
really receive nonspecific therapy.
07:07
So we've been
talking about that.
07:08
That means that our patients
need an ACE inhibitor or an ARB.
07:12
Loop diuretic again,
that's to mobilize volume off their
body and help treat that edema.
07:16
That can't happen without
a low sodium diet,
so we need that sodium to be
less than 2 grams in their diet.
07:21
Blood pressure
control us and 130/80
and hyperlipidemia
treatment with a statin.
07:28
We also can do immune targeted
therapy with prednisone.
07:31
So we typically very similar
to a minimal change disease.
07:33
We're going to give high-dose
prednisone 1 milligram per kilogram
between 12 and 16 weeks duration
with a taper over six months.
07:41
Again, very similar
minimal change disease
if her patients are
steroid dependent
meaning that we
can't tape or steroid
without them exploding again
with their nephrotic syndrome.
07:49
We can give them an alkylating
agent like cyclophosphamide
typically between
8 and 12 weeks.
07:54
Or patients who are resistant
or can't tolerate steroids.
07:58
We can give them cyclosporine
in combination with
low-dose prednisone.
08:03
Finally we can use things
like antimetabolites
like mycophenolate mofetil
in our patients who are
steroid dependent or resistant.
08:11
If your patient has no response
to the above therapies.
08:14
It's very important
that you really inquire
about a familial type of FSGS
or family history.
08:20
Because they may have that
in these are those mutations that we
talked about in the slit diaphragm.
08:25
Now, if you're patient
does have familial FSGS,
you can actually cure
them with a transplant.
08:31
Because the recurrence
is relatively low.
08:34
So for secondary FSGS,
those patients typically
get nonspecific therapy.
08:40
So they will have ACE inhibitors the
ARB blockers that we talked about
targeting that
renin-angiotensin system
in order to reduce the
inter glomerular pressure.
08:48
That blood pressure again
needs to be controlled
treatment of their hyperlipidemia
as we talked about.
08:54
If our patient is obese
and they have obesity-related
FSGS, weight loss is critical.
08:58
These are patients
that we may target
for bariatric surgery
or other mechanisms
in order to reduce their weight in
order to save their renal function.
09:06
And we want to treat that
underlying disease process
that includes
treatment of their HIV.
09:13
And anybody who is
on offense of drugs,
like pamidronate or heroin
discontinuing those drugs are
going to be of critical importance,
again, in order to have a chance
at saving their kidney function.