Friday, February 6, 2015

Study group discussion: Sarcoidosis and calcium regulation

I have a review question for sarcoidosis.

What is the characteristic appearance of sarcoidosis radiological imaging?

Lambda sign?
Panda sign?

No. Hint..That's also what tuberculosis shows positive.

BL hilar lymphadenopathy.

Tree in the bud sign.
You then differentiate it from TB ..Based on whether the lymph nodes are showing necrosis or not.

Can you elaborate on the tree in bud sign?

It's an appearance on chest CT. I read it is specific for TB and sarcoidosis.

Oh so if there is necrosis, it's Tb? If not, it's sarcoidosis?

Yup. That too can be differentiated on CT.. By looking at the lymph nodes.

I have a review question. Which cells will you see in sputum examination of a patient with sarcoidosis?

Elevated CD4/CD8 ratio.

Why is that?

I don't know exactly but CD 4 + inflammation is specific to sarcoidosis. Helps differentiate it from other non granulomatous interstitial lung diseases.

*A parallel discussion on calcium was going on, since they both are related to each other, I'm posting the calcium discussion here as well*

Percentage of dietary calcium absorbed is inversely related to intake. How is this possible?

If you take more calcium, it absorbs less? I don't know how that is possible.

The body has to maintain a homeostasis for calcium.. If reduced intake..There will be paradoxical increased receptors via Vitamin D. To maintain a constant absorption.
If increased intake..The body reduces the absorption. The mechanism..PTH is stimulated via low serum calcium.. And PTH is the one responsible to make the final active form of vitamin D.
So if calcium in the blood stabilizes, there will be reduced impulses by PTH..conversely less vitD and less absorption.

It means that if your body's need/absorption of calcium equals x.
If your intake equals x, you'd be absorbing 100% of it.
If your intake equals 2x , you'd be absorbing 50% of it.
If it equals 4x you'd be absorbing 25% of it, and so on.
At a normal steady state of absorption, the more the intake is, the less the absorption percentage of it.


Can anyone associate calcium and sarcoidosis?



Because of increase in Vitamin D by granulomas.

PTH decreases then.

Which enzyme?
And which cell is involved?

It's the interstitial alveolar macrophages that secrete alpha hydroxylase that activates vitamin D.

Is sarcoidosis a cause for dystrophic calcification then?

No, metastatic.


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