Which symptom of thrombocytopenia could involve bleeding under the skin?

The presence of ecchymosis is indicative of bleeding under the skin that appears as large bruises or discoloration due to the leakage of blood from blood vessels into the surrounding tissue. In patients with thrombocytopenia, where there is a lower than normal platelet count, the body struggles to form clots effectively. This can lead to bleeding in various forms, including ecchymosis.

Petechiae, while also a sign of bleeding, present as small red or purple spots on the skin, often occurring in clusters, and are typically smaller than ecchymoses. Epistaxis refers to nosebleeds, which is a different area of bleeding. A hematoma is a localized swelling filled with blood resulting from a break in a blood vessel but does not specifically refer to spontaneous bleeding under the skin like ecchymosis does. Thus, ecchymosis is the most accurate symptom representing bleeding under the skin in the context of thrombocytopenia.