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June 16, 2014 at 8:07 AMComments: 1 Faves: 0

Watch Out for These 7 Rashes - They Could Be Signs of a Serious Disease

By Jeffrey VanWingen M.D. More Blogs by This Author

I was asked this week - "What is the single most important piece of knowledge to possess as a doctor?" In considering this, I must answer that it is the ability to distinguish between sick and not sick. In other words, it is vitally important to know what signs and symptoms are going to get better with minimal or no intervention to those which are serious or life-threatening. 

This skill as a doctor is served mostly in reassuring patients that their symptoms are self-limited or not ultimately harmful. Occasionally, however, something seemingly minor can herald a serious illness brewing deeper. Often, this first noticeable manifestation is a rash.  

Erythema Multiforme

What It Is: The rash of erythema multiforme can be frightening. It usually presents as large and small red blotches, often with clearing in the middle giving the impression of ringlets. It is quite red and angry looking, popping up very quickly. Though the cause is officially unknown, it is likely caused by deposits from an active immune system in the small blood vessels under the skin. 

Best Case/Worst Case: The causes of erythema multiforme are seemingly a mile long. While the most common causes are obvious - a cold or other upper respiratory infection, a new medicine, recent vaccination or exposure to extreme temperatures. If no obvious cause is identified, however, concern should be given for this being a heralding sign of a blood cancer such as leukemia, lymphoma or multiple myeloma. Rarely, the erythema multiforme itself can be dangerous. If the rash is extensive and involving the mucous membranes in the mouth or genitalia, emergency care should be sought.

Erythema Nodosum

What It Is: The rash of erythema nodosum involves red, raised blotches on the shins. The red bumps are usually tender and quite broad. Younger persons in their teens are usually affected. Erythema nodosum involves inflammation of fat cells under the skin and is likely related to an immune response to some other condition.  Like erythema multiform, the causes of erythema nodosum are quite varied. 

Best Case/Worst Case: Most causes are minor such as strep throat infection, mononucleosis, medications or pregnancy.  A good portion of the time, no cause is identified.Less commonly, more serious causes lie beneath the surface such as hepatitis C, inflammatory bowel disease (Crohn's disease, ulcerative colitis), sarcoidosis (an auto-immune disease), lymphoma or pancreatic cancer.  Due to the potential for serious underlying disease, the presence of erythema nodosum without obvious cause should prompt an investigation for possible serious underlying disease.


What It Is: Dermatomyositis a condition which causes a distinct rash along with other symptoms. The rash, often the first symptom of the disease, is typically a violet or deep red patchy rash found commonly on the face, trunk and limbs. Muscle pain and weakness are often coinciding or soon to follow. Although the cause of dermatomyositis is unknown, it is linked and can even lead to more serious disease. 

Best Case/Worst Case: Autoimmune diseases such as lupus and rheumatoid arthritis can occur alongside dermatomyositis. A heart condition called myocarditis or a lung condition called pulmonary fibrosis can present as a dangerous part of the syndrome. Persons who have dermatomyositis are at increased risk of developing subsequent cancer, particularly in the pancreas, gastrointestinal tract, breast, lungs or ovaries and aggressive monitoring should take place for the next few years after diagnosis.

The Butterfly Rash

What It Is: A butterfly, or malar, rash symmetrically across the face is a potentially identifying mark of lupus.  Lupus occurs when the body's immune system attacks DNA and leaves damage to a number of organs.

Best Case/Worst Case: This sign is relatively well-known and often mistaken for a more common, much less serious condition called rosacea.The malar rash of lupus is typically red or purple and scaly. Around 50% of persons with lupus experience the rash.  If suspicion warrants, blood testing can help to diagnose lupus.


What It Is: Hives usually indicate an allergic reaction to something. They occur when immune cells in the skin called mast cells release histamine. Typically, hives are blotchy, raised and very itchy.  Most hives that we think about are acute and occur due to something that the body is exposed to. Hives can be chronic also, however.

Best Case/Worst Case: The defining duration of two months puts hives into the chronic category.  While chronic hives can occur due to recurring exposure to an allergen, they can also come from a disease within the body, notably hypothyroidism, lupus or lymphoma.  If no cause of chronic hives is readily identifiable, a medical work-up should occur.


What It Is: A waxy, puffy rash on the shins can be an indicator of thyroid disease called myxedema. 

Best Case/Worst Case: Though relatively uncommon, it can help to identify a smoldering systemic thyroid disorder.  A blood test can confirm thyroid abnormalities.

Peel of the Orange (Peau D'Orange)

What It Is: An inflamed rash of the breast is worrisome as a symptom of inflammatory breast cancer. This aggressive form of breast cancer causes a red, puffy rash on the breast.  The skin's sweat glands act as a tether for the skin and leave a pattern of dimpling which resembles the skin of an orange.

Best Case/Worst Case: Inflammatory breast cancer is uncommon and often not seen on mammogram.  It is often confused with an infection in the skin.  While infection is more common, a rash of this sort should be considered as concerning for breast cancer and addressed quickly due to its aggressive nature.

If You Have a Rash...

Most rashes are skin conditions in an of themselves. In fact, virtually all fall into the categories of bacterial, viral, fungal or inflammatory.

Shot-gun treatment with steroid (hydrocortisone), anti-bacterial (triple antibiotic), or anti-fungal cream (like Lotrimin) is a reasonable option as is observation for a few days. If the rash is accompanied by other, more systemic symptoms however such as weakness, muscle aches, numbness, bowel irregularities or fever, see a doctor.  A rash exclusively on a single breast should also prompt seeing a doctor.

Remember, rashes are common. Knowledge of warning signs indicating something more serious, though, can save a life.     

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  • This skill as a doctor is served mostly in reassuring patients that their symptoms are self-limited or not ultimately harmful.

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