Platelet ultrastructural morphometry for diagnosis of partial delta-storage pool disease in patients with mild platelet dysfunction and/or thrombocytopenia of unknown origin. A study of 24 cases

Background and Objectives. Exact diagnosis is some-difficult in patients pr esenting with a slight bleeding diathesis, prolonged bleeding times, non-sp ecific aggregometric abnormalities, and/or mild thrombocytopenia. The objec tive of this study was to evaluate the use of platelet ultrastructural morp hometry detecting a partial delta-storage pool disease in such patients. Design and Methods. Platelets from 52 patients and 15 controls were fixed i mmediately in glutaraldehyde in White's saline without anticoagulant and pr ocessed for transmission electron microscopy. Using computer-assisted morph ometry, the size and shape of the slots were measured, as were the size and number platelet of the dense- and a-granules. Ultrastructural morphology o f the above and other intraplatelet structures was observed. Results. Twenty-four cases were diagnosed as having a partial delta-storage pool disease. Mean platelet area 2.28 mu m(2)) and maximum diameter (2.58 mu m) were significantly greater in patients than in control sub(1.64 mu m( 2) and 2.25 mu m, respectively) but discoid shape was preserved. Mean dense -granule number was decreased, both per platelet and per mu m(2) of platele t area (patients 0.22 and 0.09; controls 0.42 and 0.24). Seven patients als o had a marked decrease in a-granules, resulting in a significantly lower m ean number of granules per mu m(2) (patients 2.43; controls 3.15). Addition ally, the patients' platelets significant increases in both lipid droplets and surface-connected canalicular system. Interpretation and Conclusions. A partial dense-granule deficiency, sometim es associated with partial alpha-granule deficiency, should he borne in min d faced with patients who have a slight bleeding diathesis, non-specific pl atelet dysfunction tests and/or mild thrombocytopenia of unknown origin. Pl atelet ultrastructural morphometry is useful in diagnosing this condition. (C) 2000, Ferrata Storti Foundation.