Polite Dissent

I know I’ve mentioned it before, but rashes have always intrigued me. How can the skin behave is so many peculiar ways? It’s fascinating stuff.

I’m always pleased when there is a patient with the chief complaint of “rash” on my schedule, and today was no exception. I knew the patient well; he was a fun two-and-a-half year-old with good parents.

The medical assistant checked the family in and then brought me the chart.
“What’s the rash look like?” I asked.
“It looks like worms,” she said.
“It looks like he has worms under his skin?” I said, wondering were a Midwest toddler would contract cutaneous leismaniasis.
“No,” she hurriedly corrected. “It’s a flat red rash on his arms and legs that’s all twisty and turny like a worm.”

I entered the exam room. The patient was sitting in his mom’s lap, flipping through one of the comics I keep in the room. He was playful and happy (always a good sign) and seemed to have a slight runny nose. The back of his forearms and the front of his legs showed a prominent lacelike deep red rash. It had a definite serpiginous quality to it, and I could see why my medical assistant would think of worms. There was no evidence of scratching, and other than the rash and the runny nose, the patient looked good.

“It started about four days ago,” his mother said. “At first his cheeks looked bright red, like they were wind-chapped. That faded and now this rash appeared on his arms and legs/”

There was no doubt about this rash: it was a classic presentation of the common viral illness Erythema Infectiosum, better known as Fifth Disease or Slapped Cheek Disease. Caused by Parvovirus B19, it is generally a very mild illness that doesn’t require any treatment. A child infected with Fifth disease usually develops bright red cheeks early in the course of the infection. These fade and an unmistakable lacelike rash shows up on the limbs and trunk several days later. Minor cold-like symptoms are common. The only real risk occurs if a pregnant woman is exposed to the disease, because the virus can cross the placenta to the fetus.

The derivation of the name Fifth disease is interesting. Back in the old days (the old old days — when germ theory was just being formulated), many physicians had noticed that while rashes sometimes appeared on their own, they were often associated with sickness. These illness associated rashes occurred in two broad categories. The first was the pox diseases — chickenpox, smallpox and cowpox. The second category was “everything else.” Not knowing what else to do, they took this group of diseases and numbered them, one through six. Over time, the number designations have given way to more common names, except for erythema infectiosum, which is still better known as Fifth disease.

images scrounged from the web and do not show my patient