We present the case of a 3.5-year-old boy with sudden anal blood loss at school. Sexual abuse was suspected, and, apart from anal fissures seen on sigmoidoscopy, no other clinical signs of any sort of disorder were present. As no medical explanation for the blood loss could be given, penetrating anal trauma was suggested. During follow-up consultations, there were complaints of occasional blood loss. Platelet aggregation tests and electron microscopy finally helped diagnose a δ-storage pool disease which is a rare haemostatic disorder involving the dense granules of the platelets. Although exclusion of well-known blood diseases through routine laboratory testing is a common practice in children with sudden blood loss, this case illustrates the value of more specialised investigation both from a diagnostic and forensic point of view.