Thrombocytopenia Secondary to COVID-19 Vaccination: Side Effect or Coincidence?

While widespread coronavirus disease 2019 (COVID-19) vaccination has helped achieve some control of the pandemic, vaccines have presented with side effects of their own, both common and rare. We present an unusual case of a 66-year-old who presented with severe thrombocytopenia following vaccination with the Pfizer-BioNTech mRNA vaccine. Our patient is a 66-year-old African American female with a known history of Sjogren's syndrome and hepatitis C who presented to our facility as a direct admit from our affiliated infusion clinic where routine lab work revealed a platelet count of 14,000. On arrival, she reported a one-month history of progressive tiredness, intermittent epistaxis, and bruising on her legs. Her physical exam was notable for multiple petechiae and non-palpable purpura on all four extremities. Further questioning revealed that she had received her COVID-19 vaccine booster (Pfizer-BioNTech) three weeks prior to presentation and that is when all the symptoms had started. Rheumatology was consulted and the patient was started on intravenous immunoglobulin infusion for two days and pulse dose prednisone. Her platelet count showed improvement after treatment, and she was discharged home with a platelet count of 42,000. Though largely safe and efficacious, COVID-19 vaccines can present with rare systemic side effects and physicians must have a high index of suspicion and report these cases so that more data is available for interpretation.