20 Cause of Petechiae and What You Need to Know About Them

11. Thrombocytopenia from Viral Illnesses

Many viruses can cause a drop in platelet count—a condition known as thrombocytopenia—which directly contributes to the formation of petechiae. Viruses like dengue, Zika, hepatitis C, and even influenza can temporarily suppress the bone marrow, making it harder for the body to produce the platelets necessary for blood clotting. The result? Tiny red or purple spots that may first appear on the lower legs or inside the mouth. Petechiae linked to thrombocytopenia are often accompanied by easy bruising or bleeding gums. It’s critical to get a complete blood count (CBC) test if you notice these signs following a viral illness.

12. Leukemia

One of the earliest visible signs of leukemia—a cancer of the blood and bone marrow—can be petechiae. As leukemia progresses, it interferes with the body’s ability to produce platelets, causing unexplained bleeding and pinpoint red spots. These spots often appear on the chest, arms, or legs and may go unnoticed at first. If petechiae are accompanied by persistent fatigue, frequent infections, night sweats, or swollen lymph nodes, a full blood panel and bone marrow biopsy may be necessary. Early detection is crucial, as petechiae could be your body's quiet first signal of a much larger battle ahead.