Abstract
Platelet dense granules were examined quantitatively using mepacrine-labelling method in normal subjects and in patients with congenital platelet dysfunction. A mean number of mepacrine-positive granules per platelet (MGN: mean granule number) was 5.24—0.44 (SD) in 10 normal subjects. The number of positive granules was distributed in unimodal guassian distribution and was proportional to the sizo of platelets. In this study distribution curve and platelet granule number/platelet volume (MGN/MPV) ratio were referred for evaluation. The MGNs were 1.25 and 1.38 in two cases of Hermansky-Pudlak syndrome, 1.51 in a case of Wiskott-Aldrich syndrome. In these cases the decrease of dense granules was confirmed by ultrastructural studies. Although the reduction in MGN of platelets from a patient with Wiskott-Aldrich syndrome is partly due to smaller volume of these platelets, the decreased MGN/MPV ratio reflects a net decrease of dense granules. Platelets from patients with cyclooxygenase-deficiency and with intracellular Ca transport defect, in which platelet dysfunctin is supposed to be due to impaired release mechanism, had normal MGN value and normal distribution of mepacrine-positive granules. In a patient with Bernard-Soulier syndrome MGN per platelet was increased, but MGN/MPV ratio, that is, granule numder per μ3 was within normal range. Mepacrine-labelling method was proved to be very useful for diagnosis of storage pool disease. This method could be also applied to thrombocytopenic patients in which aggregation studies and/or biochemical quantification of adenine nucleotides are not feasible.
