Megakaryopoiesis was examined in 10 patients (eight females and two ma
les) with cyclic thrombocytopenia (CT) to investigate the underlying p
athogenesis. Numbers of CFU-Meg and megakaryocytes and the mean cytopl
asmic area (mean area) of megakaryocytes at the peak, nadir, ascent mi
d phase, and descent; mid phase of the platelet cycle were determined.
The patients were classified as female cases group I(cases 1-4; previ
ously diagnosed as ITP and CT occurred during remission), female cases
group II (cases 58; persistent CT from initial diagnosis), and male C
T (cases 9 and 10). In three of the four female cases in group I, numb
ers of CFU-Meg and megakaryocytes were normal or increased persistentl
y during the platelet cycle, whereas the mean area fluctuated in synch
rony with the platelet cycle, suggesting failure of cyclic production
rather than platelet destruction, In the female cases in group II and
one female case in group I, numbers of CFU-Meg and megakaryocytes were
also normal or increased at four phases of the cycle, but the mean ar
ea did not fluctuate, remaining large during the cycle, suggesting cyc
lic destruction or platelet clearance. In contrast, in the male patien
ts values for numbers of CFU-Meg, megakaryocytes and mean cytoplasmic
area fluctuated during the platelet cycle, indicating that cyclic chan
ges in megakaryopoiesis generated the platelet cycle. These findings i
ndicate that the measurement of cytoplasmic area is useful for disting
uishing cyclic platelet production from cyclic destruction or clearanc
e in CT.