Hereditary αδ-Storage Pool Deficiency with the Abnormal Structures of the Platelet Microtubules.

The case is a 27-year-old man, who referred to us presenting the mild bleeding tendency after extraction of a tooth. Bleeding time was 3 minutes by the Duke method, and his platelet count was slightly decreased (7x10 ¹⁰ /l). His mother also has the similar platelet abnormality. They have no albinism. The peripheral smear demonstrated the abnormal platelet morphology with hypo or agranular and large forms. Almost normal platelets were also present on the smear. A platelet adhesion test showed the impaired collagen adhesion. A platelet aggregation study revealed the abnormally poor responses to adenosine diphosphate, collagen, arachidonate, U-46619, and a relatively retained response to ristocetin. Electron microscopy of the platelets demonstrated 2 populations: one with almost normal distribution of the granules, the other with marked decrease in both α and dense granules, even though the former population had the abnormal granules and the obvious vacuoles in the platelets. Flow cytometry revealed the reduced Mepacrine positive platelets and the decreased surface CD62P induced with phorbor ester in the patient. The patient platelets contained the reduced concentration of both adenosine triphosphate and serotonin, compared with the normal control. The cytoskeleton structures were examined with immunocytochemistry using the specific antibodies. Most platelets of the patient lost the typical coiled marginal bands and showed the yarnball-like structures of the microtubules, although the actin microfilaments were relatively retained. In other words, the platelets even with the almost normal distribution of the granules have a disturbed tubulin organization, which were not apparent in the leukocytes. These results suggested that some platelet-specific proteins, such as β1 tubulin, involved in the formation of the microtubules could be causative for this hereditary storage pool deficiency.