Abnormal platelet morphology Abnormal platelet granules 2012-06-02T09:47:57Z UMLS:C4023146 An anomaly of alpha or dense granules or platelet lysosomes. HP:0011883 Platelets contain two classes of granule: the alpha granules and the dense granules. During platelet activation, the contents of the granules are discharged into the lumen of the open canalicular system, from which they are then released to the extracellular space.