My dermatologist called this week with my skin biopsy and blood test results.

Microscopes revealed my purplish rashes are thickening my skin in places, wasting it in others. Inflammatory cells meant for fighting infections have clustered around my blood vessels.

My blood shows elevated levels of creatine kinase and aldolase, the former an enzyme that breaks down the creatine commonly used by athletes and bodybuilders, the latter an enzyme that helps convert glucose into energy; these enzymes presence in my blood reveal I have muscle damage.

I have dermatomyositis.

Dermatomyositis is an inflammatory disorder in which the immune system mistakes the body’s muscle and skin cells for invaders and attacks them.

No autoimmune disease diagnosis is good. But the more common ones—lupus, psoriasis, rheumatoid arthritis—have modern treatments, including advanced immunosuppressive drugs. Over 90 percent of those afflicted with such diseases in the United States live a full life.

Dermatomyositis affects less than five in 100,000 people. Odds are my dermatologist has seen only a handful of cases in his lifetime (even in a city of five million). By contrast, over three million Americans have psoriasis. Lupus is about half as common as psoriasis, affecting 20 to 70 in 100,000.

To compare these autoimmune disorders with the more familiar, as many as 35 million Americans every year get the flu; 38.4 percent of Americans have or will have cancer.

An estimated 16,000 people in the United States have dermatomyositis. Considering the world’s third largest population is spread out over the world’s fourth largest country, the chances you ever meet one of them is very small.

None of these figures are to downplay the symptoms and suffering of other autoimmune, infectious disease, or cancer patients. These merely illustrate the rarity. If lupus is a medical-school disease, then dermatomyositis is that annoying challenge question some irritating MD-PhD-MPH snuck onto his medical student’s exams (interesting med-school fact: to the untrained eye, skin biopsies from dermatomyositis and lupus look very similar under a microscope).

Dermatomyositis is an inflammatory disorder in which the immune system mistakes the body’s muscle and skin cells for invaders and attacks them.

Major symptoms of dermatomyositis

• Itchy, painful, bleeding purplish-reddish rashes occurring along the shoulder line like a shawl or in a V-shaped pattern above the breasts
• Gottron’s papules, which are scaly, red rashes on the knuckles, elbows, and knees
• Muscle weakness

Other symptoms of dermatomyositis

• Rashes around the eyes and on the face made worse by exposure to sunlight
• Swollen, sometimes painful joints
• Difficulty breathing from weakening lung muscles or interstitial lung disease
• Difficulty swallowing
• Calcium deposits

By modern standards, treatments for dermatomyositis are primitive. Every single drug used to combat any form of myositis was developed and used for something else like treating cancer or malaria. All of these have serious, even life-altering or life-threatening side effects. Corticosteroids are the first-line treatment, but they are not without serious risks; long-term users can develop additional muscle weakness, peptic ulcers, steroid dementia, osteoporosis, or Cushing’s syndrome.

Of course, doing nothing is not an option. Without treatment, dermatomyositis kills you.

So where does that leave me? Where does it leave others battling some form of myositis?

I don’t yet know.

Exercise and physical therapy will be very important and may one day save my lungs or my life. Stem-cell therapy may eventually work. New wonder drugs and therapies are being invented all the time. New uses for current drugs are always being explored. Meanwhile, there’s prednisone. And I’m not giving up on myself, on my disease, or on the marvels of modern medicine.