As Covid-19 started to spread across the United States earlier this year, dermatology offices began to see suspicious signs on some patients’ skin: Red or purple toes, itchy hives, mottled bumps on fingers, a lacy red rash that spread across legs and arms.

But were those truly associated with the novel coronavirus? After all, many other factors could be at play.

“Many viral infections can trigger a skin rash, so when you catalog these case reports, you have to have other data. Was the patient on a medication a week before the rash began? Are there other possible causes?” asked Dr. Art Papier, an associate professor of dermatology at the University of Rochester Medical Center in New York.

“This is the challenge that Covid-19 brings up. With these different types of presentations and different rashes, is it hives because the patient just has hives or hives related to Covid-19?”

Case reports began to be released in medical journals. The latest, published Wednesday in the journal JAMA Dermatology, describes the experiences of four patients with severe Covid-19 who were admitted to hospitals in New York City in March and April.

The patients, ages 40 to 80, had discoloration of their skin as well as lesions called retiform purpura, according to the research report. Biopsies were performed for each patient and they showed that the patients had a type of vasculopathy, meaning that their blood vessels were affected.

The researchers — from NewYork-Presbyterian/Weill Cornell Medical College — wrote in their report that the skin discoloration could represent partial occlusion or blockage of blood vessels, and the retiform purpura could represent full blockage.

Such rashes and discoloration of the skin can be a “clinical clue” to there being possible blood clotting in the body, the study said.

Since early on in the pandemic, doctors have noticed that severe Covid-19 could cause abnormal blood clotting in patients.

The report comes with some limitations, including that the researchers were not able to confirm the precise timing of when rashes and other issues with the skin first appeared for each patient. Also, more research is needed to determine whether similar findings would emerge among a larger group of Covid-19 patients.

Yet overall, the researchers wrote in their report that physicians caring for Covid-19 patients should be aware of skin discoloration and rashes as “potential manifestations” of abnormal underlying blood clotting.

Medical reference: CNN Health