Petechiae

Petechiae are tiny (1–2 mm) flat red, brown or purple spots caused by small amounts of blood leaking from the smallest blood vessels (capillaries) into the skin. A distinguishing feature is that, unlike many rashes, they do not blanch — they stay visible when you press on them or stretch the skin — because the blood is outside the vessels rather than flowing through them. Sometimes petechiae are entirely benign and local: they can appear on the face and around the eyes after violent coughing, vomiting, straining or crying, from the burst of pressure. But when petechiae are widespread, appear without an obvious cause, or come with easy bruising, nosebleeds or bleeding gums, they are an important sign — most often of a low platelet count (thrombocytopenia), because platelets are what plug these tiny vessel leaks. That can arise from immune destruction of platelets (ITP), from bone-marrow problems that reduce platelet production (aplastic anaemia, leukaemia, myelodysplastic syndrome), from severe infection, or from certain medicines. Less commonly, petechiae reflect a blood-vessel inflammation (vasculitis) or a clotting problem. Petechiae accompanied by fever and feeling very unwell can be a sign of a dangerous infection such as meningococcal sepsis and is an emergency.

• Straining — coughing, vomiting, crying or lifting, causing local facial petechiae; usually harmless.
• Low platelet count (thrombocytopenia) — the most important cause; from immune destruction (ITP), marrow problems (aplastic anaemia, leukaemia, MDS), or medicines.
• Severe infection or sepsis — petechiae with fever and feeling very unwell can be an emergency (e.g. meningococcal sepsis).
• Blood-vessel inflammation (vasculitis).
• Clotting problems — including certain medicines that affect clotting.

The key first test for unexplained or widespread petechiae is a full blood count, above all the platelet count — a low platelet count is the commonest and most important explanation and immediately reframes the picture. A blood film is examined to look at the platelets and check for abnormal cells that might point to a marrow problem such as leukaemia. Clotting tests (prothrombin time and APTT) assess the clotting system, and depending on the picture, tests for infection, immune conditions or vasculitis may follow. Mediora.AI can surface a low platelet count, an abnormal white-cell picture or a clotting abnormality on your results so the pattern behind petechiae is visible; the interpretation, and any bone-marrow work-up, belong with a doctor.