A concerned mother brought in her seven-year-old son. On collecting the boy from school, she had noticed a rash of fine red dots that was most prominent behind his ears but extended to the face and forehead. The patient was well, with no other symptoms. He had not been coughing, vomiting or straining to open his bowels. On examination, an impressive rash of densely packed fine petechiae mainly distributed on the face was found. There were a few spots on the neck and chest, above the nipple line.
The boy was active, with no fever. The location of the rash within the distribution of the superior vena cava suggested a mechanical cause, but the history failed to reveal a precipitant. He was too well for this to be meningococcal disease or a manifestation of acute leukemia. In the absence of an obvious cause, immune thrombocytopenic purpura needed to be excluded. What could be the most…
