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Platelet ultrastructural and functional studies in myelodysplasia
D Blockmans1, M J Heynen, G E Verhoef
1Department of Internal Medicine, University of Leuven, Belgium.
Abstract:
We studied the platelets of 8 patients with myelodysplasia aged 49-77 years, using both ultrastructural and functional techniques. Five of the 8 patients were classified as having refractory anaemia, and 3 as refractory anaemia with excess of blasts (RAEB). Electron microscopically, the myelodysplastic patients had in addition to normal ones, platelets containing significantly less alpha-granules. In part of these hypogranular platelets, the dense tubular system was abundant, but in contrast with normal platelets, it was not dispersed between the other organelles, nor did it form a membrane complex with the open cannalicular system. From a functional point of view, collagen-induced shape change was the most frequently disturbed parameter: there was a total loss of collagen-induced shape change in 5 patients. In 2 patients, there was a complete lack of response to collagen in platelet-rich plasma (both shape change and aggregation); in one of them, there was also a total loss of adenosine triphosphate secretion in response to all inducers tested. After 4 years of follow-up, 5 patients had died, of whom 3 were RAEB patients. An initial complete absence of collagen-induced shape change was found in these 5 patients, while in the 3 patients who were still alive at the end of the follow-up period, collagen-induced shape change was normal in 2 and slightly diminished in one.
Insights
Platelet abnormalities, including fewer alpha-granules and impaired collagen response, are common in myelodysplastic syndromes (MDS). These platelet defects correlate with disease severity and patient outcomes.
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem cell disorders.
- Platelet dysfunction is increasingly recognized as a feature of MDS.
Purpose of the Study:
- To investigate ultrastructural and functional platelet abnormalities in patients with myelodysplastic syndromes.
- To correlate platelet findings with clinical outcomes.
Main Methods:
- Ultrastructural electron microscopy of platelets.
- Functional platelet assays including collagen-induced shape change, aggregation, and adenosine triphosphate secretion.
- Clinical follow-up of patients.
Main Results:
- MDS patients exhibited hypogranular platelets with abnormal dense tubular system organization.
- A significant proportion of patients (5/8) showed a complete loss of collagen-induced shape change.
- Complete loss of collagen-induced shape change and adenosine triphosphate secretion was observed in some patients.
- Absence of collagen-induced shape change was associated with mortality, particularly in refractory anemia with excess of blasts (RAEB) patients.
Conclusions:
- Platelet ultrastructural and functional defects are characteristic of myelodysplastic syndromes.
- Impaired collagen-induced shape change is a significant finding in MDS platelets.
- Platelet dysfunction may serve as a prognostic marker in MDS, correlating with patient survival.