Pitiriasis Rosea – The Christmas Tree Rash

I was happy today to have a case of Pitiriasis rosea today in the office to show off to my medical student. The 14 year old girl with the rash was a great sport to let me show her torso rash to my young male 3rd year student. I love diagnoses that are easy, where the condition is not serious, and especially when they have a fun name. Pitiriasis as a general term refers to a flaking or scaling condition and comes from the Greek word for bran. Add to that a differential diagnosis that includes syphilis and a distribution on the skin of the torso compared to a Christmas tree and you’ve got a great teaching case.
Pitiriasis rosea is usually a mild and self limited skin rash felt to be caused by a virus, possibly a Human Herpes Virus of the group 6 or 7 which can cause Roseola infanatum in very young children possibly presenting differently in older children or adults. It is felt to usually be non-contagious, although small outbreaks have been reported. The rash usually first shows up as a large reddish flaky patch, called a herald patch because it heralds the onset of the disease, and followed by multiple smaller reddish patches that are often oval shaped and run with the skin lines of the torso. The skin lines of the torso run diagonally sloping upwards as they run from the mid anterior abdomen outwards, so the distribution is described as a Christmas tree distribution. The rash is sometimes preceded by a minor illness, and the rash sometimes itches mildly to more severely. The good thing is that it resolves without treatment, usually in about 6 weeks or so.
As a medical student we were always drilled to remember that secondary syphilis can present with a similar rash, although I suspect most of us have never actually made a  diagnosis of a case of secondary syphilis that presented this way. Still I made sure to quiz my medical student today on this to keep up the tradition of thinking of zebras as well as horses when we hear hoof beats.

Here is a link to several photos of Pitiriasis rosea.

2 Responses to Pitiriasis Rosea – The Christmas Tree Rash

  1. My daughter, who is 13, has this currently. The mark appeared a few weeks ago at the base of her throat. It was round like a big red mosquito or bug bite. She woke up with it, so we thought bug. It did not really get better, and then appeared to flatten and spread out, not unlike a ringworm. So we home treated it somewhat, but it did itch some so after a couple weeks we went to the doctor. He agreed it was probably not ringworm, but perhaps contact dermatitis. No other bumps or rash had appeared yet. Now a week later we find new bumps and rash type places, on her back, chest, ribs{generally from the neck down to her upper hips.So a doctor appt is made and we go again. Of course by then it was apparent what it was. Pitiriasis Rosea. My comment about it is that as a small child about 5 yrs old she was diagnosised with this too. The herald mark was on the back, then spread on her back and definitely has the “Christmas tree” mark. I’ve read usually you don’t get it twice but my child has. She appears fine, she may have had a sickness not too long before the first mark appeared, but school had started and everyone catches stuff the first few weeks back at school. Also my daughter has a goiter on her Thyroid with multi nodules. I don’t suppose it has anything to do with the other. She is not on Thyroid meds at this time, but more than likely she will be she gets older. Too much to explain about that subject. I just decided to comment because she has had this twice. Thank you.

  2. I just came from the Doctor’s office with the same situation. The Dr thought that this was the “best” case she’d seen in a long time. She too called in her student to quiz her… and they even took pictures. So here I am looking up more information. His case cover all of his body from neck to ankles.

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