Hi, everybody.
It's Rishi Agrawal, and in this video, I want to talk about the cystic lung
disease, lymphangioleiomyomtosis or LAM.
This is the roadmap that we're going to use today.
I'm going to start with my three take home points for radiologists to know,
and then we're going to go a little bit into the background and epidemiology,
and then we're going to talk
about the clinical practice guidelines that are relevant for radiologists.
And then we'll go into some examples and the imaging appearance.
Here's my take home points for radiologists.
The first is that the primary manifestation of the disease
on HRCT is multiple thin walled lung cysts with a uniform
apical to basilar distribution, which means they're not
upper low predominant, they're not lower low predominant.
They affect the upper lobes and lower lobes about equally,
and the cysts are usually less than 2 cm in size,
although they can be larger in patients with more severe disease.
The second
take home point is that it almost exclusively affects females.
And you'll hear this term a lot in the literature of "child-bearing age",
which basically means that the patients are usually between
the ages of 20 to 60 when they present.
And possibly have AMLs or angiomyolipomas
in the kidneys or lymphangioleiomyomas in the abdomen or pelvis.
And then finally patients often present with a pneumothorax.
So if there's a young female who comes into the ED with a spontaneous
pneumothorax, meaning there's no known cause and the patient is not a smoker,
then it might be prudent to suggest the diagnosis
so that that patient can get further testing.
Pathologically, LAM is considered a low grade
neoplasm, and it's characterized by proliferation of these cell clusters
called LAM cells, which resemble smooth muscle.
And the origin of these cells is not fully understood,
but these LAM cells can proliferate in the lungs, kidneys and lymphatics.
In the lungs, they cause cysts formation.
In the kidneys they can cause AMLs.
And then in the lymphatics they can cause chylous effusions
in the chest and in the abdomen, as well as these low density
lesions, usually in the retroperitoneum called lymphangioleiomyomas.
And there's two classifications of LAM.
In most cases it's an isolated disease and that's called sporadic LAM.
But in about 15% of patients with LAM,
it's associated with tuberous sclerosis.
And it's these cases in which men can occasionally be affected.
Now the imaging findings are a little bit different
between sporadic LAM and tuberous sclerosis-associated LAM.
In S-LAM, lung cysts are more common
and in TSC-LAM,
patients are more likely to have renal AMLs and lymphangioleiomyomas.
And then also in patients with tuberous sclerosis,
there's additional radiologic and clinical findings,
including brain lesions that are absent in patients who have S-LAM.
I want to talk briefly about these clinical practice
guidelines that came out in 2017 and it goes over LAM
diagnosis and management specifically talking about HRCT.
This is one of the tables that was published in the paper
and it says a definite diagnosis of LAM can be established
if a patient with compatible
clinical history and characteristic imaging of the chest, meaning
uniform lung cysts, has one or more of the following features.
And it goes over seven of them.
Now some of these are clinical features, but I want to focus on these three
because these are imaging features that you may potentially see on CT:
Renal AMLs, chylous effusions and lymphangioleiomyomas.
Renal AMLs will show up as a low density fatty lesion in the kidney.
A lymphangioleiomyoma is also usually
a low density lesion that you'll see in the retroperitoneum.
And I'll show you examples of both of these.
And then chylous effusions.
Now on imaging, chylous effusions will usually look no different
than regular, simple, transudative, plural effusions.
Very rarely will you see macroscopic fat in chylous effusions,
but it's something that you can suggest on the CT.
Let's look at a few examples now.
Here's a patient who was in her early forties, and she presented
to the emergency department with right sided chest pain and dyspnea on exertion.
If I zoom in here, you can see that there's a right pneumothorax,
and if I go down to the base,
you'll see that there's a horizontal line.
Whenever you see a horizontal line in radiology, I want you to think about
an air fluid level, not simply a fluid level, but an air fluid level,
meaning this patient has a hydropneumothorax.
If it were just a simple pleural effusion
rather than a horizontal line here at the edge, you'd see a meniscus
because the fluid would be creeping up the side between the lung and the pleura.
So because of the patient demographics and because of the fact that we have
a hydropneumothorax, I'm going to be very suspicious for the diagnosis of LAM.
And this is probably a chylous pleural effusion.
But even looking very critically at the lung here,
I don't think I would call anything in this patient.
And in fact, in most patients who have early disease,
the chest x-ray will often be normal.
Despite that, we
suggested that the patient has LAM and that she should get a further workup.
So she went ahead to get a chest CT which was done a few days later,
and on CT, you can see that there's
numerous cysts throughout both lungs.
And if I scroll from the apex to the base,
you can see that there's no real apical to basilar gradient.
The number of cysts is about the same in the upper lungs
as it is in the lower lungs.
And the reason why this patient has subcutaneous emphysema
here is because she had a chest tube placed.
What you'll also notice here is that there's probably
a little loculated pneumothorax in the left, major fissure.
And not only does the patient have a small right pleural effusion, which we saw
on the chest x0ray, but she also has a little left pleural effusion as well.
Most of the cysts are fairly small
with some of the larger cysts going up to about 1.5 cm in size.
This is a classic appearance of LAM.
Now, a couple other things that you can do is look at the coronal images
to look at the apical to basilar gradient.
And then if you're having trouble deciding whether there are cysts or not,
in this case, it's not that much of a diagnostic dilemma,
you can use your minimum intensity projection
images (MinIP), which will make the cysts stand out even more.
So this is a classic case of LAM
in a patient who presented with a pneumothorax
and the pleural effusion did turn out to be chylous fluid.
Let's take a look at another patient.
Here's a different patient with LAM.
And you can see that there's uniform cysts throughout the lungs.
These cysts are a little bit bigger than the patient who we just saw.
And that usually means
that the patient is a little bit further along in their disease course.
But I really wanted to show you
the upper part of the abdomen, which we catch on the chest CT.
And you can see that there's these lesions in the upper
poles of the kidneys, like there's one right there on the right.
And then if we go down a little bit further, you can see more on the right
and you can see another one there on the left.
And these
lesions are angio male lipoma is or animals, which are lesions
containing components of blood vessels, smooth muscle and adipose tissue.
And the presence of fat on CT is the easiest way to diagnose these.
But, sometimes they can have very little fat, and you need MR
to look for that chemical shift artifact on out of phase imaging.
But even on that, occasionally AMLs don't have any fat
and you need a biopsy to differentiate it from RCC.
AMLs are more common in TSC-LAM, usually seen in 90% of those patients
compared to about 30 to 60% of patients with S-LAM.
Let me show you another case.
Here's another patient who had LAM, and this patient
had more confluent cystic lung disease that you can see here.
But what I really want to show you is the abdomen.
So starting right here you can see that there are
these low density lesions in the retroperitoneum.
And if I continue to scroll, you can see that it goes all up and down
the retroperitoneum into the iliac chain.
And when we go over to the right, you can see that
some of these have some soft tissue component as well.
So these are lymphangioleiomyomas,
which is another thing that you can see with LAM.
And these are seen in approximately 15% of patients
as opposed to the AMLs which are more common.
These lymphangioleiomyomas are characteristically
found in the retroperitoneal region.
And if the patient has these lesions,
they may have symptoms like bloating or edema.
And the symptoms have this typical
diurnal variation where it may worsen over the course of the day.
OK, so this is another characteristic finding that you'll see
in patients with LAM, although not as common as the AMLs.
Here's the last patient
I want to show you and I want to start with a chest x-ray here.
And you'll notice two things on the chest x ray.
The first is that there's flattening of the diaphragm,
and that's a sign of hyperinflation.
And the second thing is that if we zoom in, you can see that
the patient has too much reticulation in the lungs.
And oftentimes reticulation is a sign of fibrosis
like UIP or NSIP or chronic HP.
But in this case, we have reticulation plus we have lung hyperinflation.
That combination should make you think of cystic lung disease.
So this patient was already advanced in their disease
and they had a known diagnosis of LAM.
But I just wanted to show you what it looks like on chest x-ray.
On CT, they have an additional finding that we didn't see
in the other examples, and that's that the patient has ascites.
So remember that these patients can have chylous pleural effusions
as well as chylous ascites.
This patient, if we look at their retroperitoneum also has low density
lesions in their retroperitoneum consistent with lymphangioleiomyomas.
So remember
that the chylous effusions, either plural or ascites,
will usually just look like simple pleural fluid.
It's rare that you'll see macroscopic fat
in the pleural effusion or in the ascites.
OK, so those are the examples that I have for you today.
Let's quickly talk about the differential diagnosis before we end.
If you have a new patient with cystic lung disease, these are probably the
three top things you're thinking about in your differential pulmonary Langerhans'
cell histiocytosis, lymphocytic interstitial pneumonia and Birt-Hogg-Dubé.
So for PLCH, remember that these are usually going to be smokers
and then the cysts have this bizarre shape
rather than uniform nice round cysts with LAM.
And then remember that patients have nodules in PLCH,
and that the nodules become the cysts which is not something you see with LAM.
And then finally it spares the bases.
So PLCH is a typically upper lung
predominant disease, whereas LAM has no apical basilar gradient.
LIP is usually associated with connective tissue disease
and most closely associated with Sjogren's,
although you can see it with other things like lupus.
But the main thing with LIP that differentiates it from LAM
is that the cysts are lower lung predominant in LIP.
And then finally Birt-Hogg-Dubé is a rare cystic lung disease,
and the cysts in Birt-Hogg-Dubé are also lower lung predominant.
That's one way you can tell.
They're also larger cysts that abut the pleura in Birt-Hogg-Dubé
as opposed to LAM.
And then finally, Birt-Hogg-Dubé is a familial disease,
so it runs in families and it's associated with renal tumors.
So even if the patient doesn't have a history of renal tumor or you don't see
any renal tumors on the patients imaging, if you dig into the family
history, a lot of times the family members will have renal tumors.
So that's how you can tell it's Birt-Hogg-Dubé.
And then you can also tell just by genetic testing.
So that's a quick differential diagnosis for LAM.
OK, that's all I have for you for this video.
If you have any questions about this topic, let me know in the comments below.
Thanks.