Internal medicine and rheumatology specialist Siobhan Deshauer, MD, reviews the underlying pathophysiology of common skin conditions.
Following is a partial transcript of the video (note that errors are possible):
Deshauer: Consider this. Your body is made up of 79 organs working together to keep you alive. Your skin is by far the largest one and it's unique in how accessible it is to see and to touch. Serious issues with your heart, liver, bowels, and even your hormones can show up in your skin. In some cases, knowing what to look for can mean the difference between life and death, so let's dive into it and discover what your skin says about your health.
Did you know your diet can have a direct impact on your skin? And no, I'm not talking about acne. This is dermatitis herpetiformis, and as the name suggests, it looks a lot like herpes -- tiny, fluid-filled blisters that are grouped together. But don't let the name fool you. This rash has nothing to do with the herpes virus. It's actually a direct result of a diet high in gluten, a protein found in wheat, barley, and rye.
This patient has celiac disease. Some combination of risk genes and environmental triggers have caused the immune system to react to gluten and mount an attack. Part of that attack is creating antibodies, a type of protein that binds to perceived threats in the body targeting it for destruction by the immune system. Unfortunately, the immune system mistakenly attacks an enzyme in the small bowel called tTG. This is one of the many ways that the immune system destroys the lining of the small bowel in celiac disease, causing weight loss, bloating, diarrhea, and nutritional deficiencies.
But what does that have to do with the skin? Well, some people with celiac disease also produce antibodies against a similar enzyme called eTG that's found in the skin. Do you see where I'm going with this? This leads to immune activation in the skin, which causes a horrible, itchy rash. So we can get a clue of what's going on in the small bowels just by looking at the skin.
How do we know it's not herpes if they look similar? Well, first off the location. It would be really unusual to get herpes on your elbows and your knees, but usually we do a biopsy anyway. A small piece of skin is cut out and sent to the lab where they do special staining to check for antibodies in the skin. Now, this is a really cool image because you can actually see markers attached to the antibodies in the skin that are lighting up as fluorescent green. This confirms the diagnosis. Luckily, the rash and the itch will usually clear up completely after switching to a strict gluten-free diet.
OK. Now, this is a xanthoma, which is essentially a fatty plaque in your skin. Usually they don't cause any symptoms, but sometimes patients will come in because they are a nuisance or because they have cosmetic concerns. But if I see one of these, I'm immediately concerned about what's going on internally. If there are fatty plaques that are building up in your skin, then they could also be building up in other parts of the body like the coronary arteries of your heart. You've got to ask the question why are your lipid levels so high? Sometimes it's a genetic condition, but often it's linked to diabetes or liver disease.
A fun fact about xanthomas is that you can often tell what type of lipid is involved based on where they appear in the body. For example, eruptions like this can happen along the shoulders, arms, or buttock and it's a sign of high triglycerides. In cases like this, my biggest concern is underlying diabetes. Whereas xanthomas that form in the tendons, particularly in the Achilles tendon at the back of the ankle, are often associated with a genetic condition called familial hypercholesterolemia and that causes high LDL [low-density lipoprotein] cholesterol.
While we're on the topic of things depositing in the skin, here is a cause that often gets overlooked and misdiagnosed. Gout is a type of arthritis that's caused by uric acid crystals that build up in the joints. The flares come on rapidly and they cause excruciating pain with redness and swelling. It used to be considered the disease of kings because it's typically brought on by rich foods that contain purines like red meat, seafood, and alcohol -- things that were usually only accessible to the wealthy.
King Henry VIII famously suffered from gout, among other conditions, and by the end of his life he was so incapacitated that he had to be carried around in a special chair. With such severe gout and no treatments at the time, it wouldn't surprise me if he had also developed skin deposits. The same uric acid crystals that irritate the joint can deposit in the skin, forming these lumpy lesions called tophi. You can see them around the joints, particularly in the fingers and toes, and even on the outer edge of the ear. Even more concerningly, those same crystals can deposit into the kidneys and that can form kidney stones and it can actually cause permanent kidney damage. Luckily, we now have really effective medications to lower uric acid levels, something I'm sure Henry VIII really wishes he had access to.
Next, let's talk about skin tags. I'm sure you've seen these before. They are quite common and they usually show up in areas where there is friction against skin or clothing like eyelids, neck, or armpits. While skin tags themselves are harmless, they can be a warning for certain metabolic conditions like diabetes. Keep in mind that skin tags do have a genetic component and they can run in families. But if you do have multiple skin tags, particularly around the neck or in the armpits, it's worth getting screened for diabetes with a blood test called hemoglobin A1c.
Here is another common one that I'm sure you've seen. People will often call these age spots, although I think the best name I have ever heard is barnacles of aging. Don't you love it? The medical term is seborrheic keratosis, or SK for short, and I always feel like they look kind of waxy like a blob of candle wax. When you touch them, it's tempting to think that you can just peel them off, but I would strongly advise against that. They're harmless in and of themselves. But if you suddenly develop a massive eruption of these lesions and you see them all over, that could be the first sign of a cancer. It's called the Leser-Trélat sign and it doesn't mean you for sure have cancer, but it's concerning enough that you definitely need to get checked out.
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Siobhan Deshauer, MD, is an internal medicine and rheumatology specialist in Toronto. Before medicine, she was a violinist, which is why is called Violin MD.