Doctors search for missing link between COVID-19 and ITP


Hospitalist Sarah Stone, MD, arrived for her day shift at Sharp Chula Vista one day in late December. The ICU and hospital wards were still overflowing with COVID-19 patients. But over the previous couple of months, she’d also seen more and more recovered patients presenting with a myriad of symptoms: pulmonary emboli, cardiomyopathy, a shocking case of aspergillosis, and those rare cases of “long COVID,” the patients who just can’t get better.

This morning it was a woman in her 30s. She felt fine, but 2 weeks after recovering from COVID-19, she had unexplained bruising on her arm, a petechiae rash on her legs, and her gums were bleeding. Once admitted to the emergency department, her platelet count of 5000/mm3 was a dead giveaway of immune thrombocytopenic purpura (ITP).

In Dr. Stone’s experience, new and otherwise unexplained symptoms so soon post COVID-19 can’t be written off as a coincidence without some additional consideration. But a quick preliminary search of the literature during her rounds came up almost empty. She found one report with three cases of post-COVID-19 ITP. But other online resources made no mention of it. Kenneth Johnson, MD, the hematologist/oncologist consulting on the new case, told Dr. Stone he’d seen one other case of post-COVID-19 ITP only earlier that month. Dr. Stone called a sister hospital. They’d seen one other case just weeks before.

“I was surprised to find just three cases in the literature when we had seen three among us in a matter of weeks,” Dr. Stone said in an interview. Something was missing.

A missing link

ITP is caused by an immune reaction against a patient’s own platelets. Platelet numbers drop, causing easy bruising, bleeding gums, and internal bleeding. Acute cases can usually be resolved within 3 months, but for some patients the condition can be extended or even chronic.

“We know that infections like influenza can cause ITP, so in this light, [COVID-19-associated ITP] might not be surprising,” Gerard Jansen, MD, PhD, an internist and hematologist in Rotterdam, the Netherlands, said in an interview.

Dr. Jansen and colleagues recorded three cases of post-COVID-19 ITP in May 2020 – the report Dr. Stone had found during her shift. Two patients developed ITP several weeks after COVID-19 and responded to treatment with corticosteroids and intravenous immunoglobulin G (IVIG). The third patient, however, died of intracerebral bleeding while still battling COVID-19. He was retrospectively diagnosed with COVID-19-associated ITP.

A deeper dive into the literature uncovers additional case reports from India, France, the United Kingdom, Turkey, and one from China as early as January 2020. A September 2020 review of ITP secondary to COVID-19 included 23 papers and a total of 45 patients. The review authors noted that more than 70% of cases occurred in patients who were aged over 50 years and 75% had had moderate to severe COVID-19 infections. However, the sample size of 45 is too small to definitively describe what’s happening in the overall population.

ITP’s link to COVID-19 gained a media spotlight after the Miami obstetrician, Gregory Michael, MD, developed ITP days after getting the Pfizer COVID-19 vaccine. In early January, after 2 weeks in the ICU, Dr. Michael died of a hemorrhagic stroke caused by the low platelet count.

Pfizer said in a statement that the company is “actively investigating” the case, “but we don’t believe at this time that there is any direct connection to the vaccine.” Other experts have said the timing, particularly in a relatively young and healthy man, means a link to the vaccine is possible or even likely, but final results won›t be known until the Centers for Disease Control and Prevention finishes its investigation.

But “it is quite unusual to die from ITP,” San Diego hematologist Dr. Johnson said in an interview. In his more than 20 years of practice, he has never had a patient die from the condition.

For his part, Dr. Jansen, the hematologist in Rotterdam, said that at this point we just don’t know if there’s a link between the vaccine and ITP. Both infection and drugs are well established causes of ITP, so with that general mechanism or pathology in mind it makes sense that COVID-19 and the vaccine could instigate ITP. But it would be very difficult to prove in just one instance, he said. And considering the millions who have thus far received the vaccine without incident, and the known risks and dangers of COVID-19, “we still advise to vaccinate,” he said.


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