Sarcoid versus Scleroderma

I always get mixed up when it comes to sarcoids and sclerodermas when written on a requisition.  Currently we perform imaging on these patients to help the clinicians to determine the extent of their patient's disease, but I still get confused as to the nature of the disease and their processes.  So this portion of the blog is partly to help me and anyone out there that are in the same position.  I have tried to put this into a chart format, but it doesn't translate well into the blog.

Sarcoid:
This is an inflammatory disease that can potentially affect multiple organs within the body.  It most often starts within the lungs or lymph nodes, but it does not limit it self to these areas.  The inflammation (sarcoidosis) is not necessarily caused by an autoimmune response, since this is not an autoimmune disease, but the cause of this inflammation is uncertain.  The most distinguishing feature about sarcoids is that they deposit granulomas (microscopic lumps of inflammation).  They sometimes clear up on their own or they can become fibrotic if they remain in the body if they do not heal.

The most famous entertainer to die from sarcoidosis was Bernie Mac.  His condition was primarily localized to his lungs, but sarcoids, like I mentioned before can affect any organ.  Here at our facility we image and follow these patients when they become part of the CADRE study.  CADRE represents the Cardiac FDG-PET Registry Study.  As part of the cardiac program, we look at the extent of their disease via a whole body PET/CT, which we append to their Tc-99m myocardial perfusion studies.  Along with the whole body PET/CT, we will perform a quick FDG viability study of their heart while in the department.  Most of these patients have their cardiac workup prior to coming to PET.  Approximately 25% of all sarcoids involve the heart, and about 13-25% of all sarcoids deaths are related to cardiac insufficiencies such as heart failure, ventricular tachyarythmia or conduction disturbances.

Fig. 1  Extensive uptake of FDG within the thorax, liver, spleen and both kidneys, correlating with the patients known sarcoidosis.

We also perform gallium-67 whole body imaging to localize the areas of inflammation, in particular the lungs.  But quite honestly, we do not perform these routinely, and having said that, I don't think I have ever seen one that was positive.

UPDATE January 2, 2012:  I will take back that last comment about not seeing a positive gallium scan for sarcoidosis.  The image below was taken 48 hours post Ga-67 injection.  A whole body gallium scan was performed and there was uptake within the lungs consistent with sarcoidosis.

Fig. 2  Uptake in the hilum and the lungs, consistent with sarcoidosis

Scleroderma:
This is the result of inflammation in connective tissue featuring the formation of scar tissue (fibrosis) in the skin and organs of the body.  Scleroderma is an autoimmune disease, as the result of an overactive immune system.  They have specific antibody markers such as ANA, anticentromere or antitopoismerase in their blood stream which suggests autoimmunity.

We perform gallium imaging for scleroderma, but rarely.  I have not come across this condition with regards to the patient's history for PET/CT imaging.... yet.

I do not have any images to show from our facility and there isn't much on the web either.

Certification Exam - Student Questions

Q2.  When doing myocardial perfusion study, patients are asked to fast for 3/4 hours before the study, either rest/stress. For stress, the purpose is to minimize the possibility of vomitting right? But what is the purpose of fasting during rest??

A2.  I thought they taught you this already at the school and in clinical.  

Anyway one of the main reasons why they need to fast for both rest and stress is to reduce the gut uptake.  Remember the biodistribution of sestamibi is uptake in the liver.  If they have eaten in the morning there is potential of obscuring the inferior portion of the left ventricle due to gallbladder secretions that help with the digestion of food.  The secretions into the small bowel can cause the loops of bowel to limit the visualization of the inferior wall.

However, with Myoview they claim that there is less liver uptake when imaging.... but most facilities still recommend that the patients fast before having their myocardial perfusion imaging.

Check this article out.  It's an older article.

Myocardial Technetium-99m-Tetrofosmin and Technetium-99m-Sestamibi Kinetics in Normal

Subjects and Patients with Coronary Artery Disease


And check this out as well, quantum, this gives an explanation of some of the things that I mentioned above in a case study.

I will follow up again with this answer with more details, later on.... but for the time being I'll leave with this.  The SNM guidelines do not provide much of an explanation.