May‐Hegglin Anomaly: A Defect in Megakaryocyte Fragmentation?

Abstract

S ummary . Studies have been performed on six members of one family with May‐Hegglin anomaly (MH) five of whom manifested a mild bleeding tendency. All were thrombocytopenic (25000–1420007/μl). Platelet kinetic studies ( 51 Cr) showed normal survival (two autologous, one MH to normal, one normal to MH). Mean platelet volume was increased; content (per platelet) of cholesterol, phospholipid, and tyrosine was elevated 3‐ to 6‐fold. Total body platelet mass calculated from these parameters was normal. Tests of platelet function demonstrated normal adhesiveness to collagen, normal prothrombin consumption, and enhanced platelet factor 3 activity. Bleeding time was prolonged ( 5/5 ), platelet retention by glass beads was diminished ( 3/3 ), clot retraction was poor ( 5/5 ), and aggregation by ADP, adrenaline and collagen was similar to that of normal platelets at the same low concentration. It is considered that the bleeding tendency probably reflects thrombocytopenia per se as do those tests of platelet function that are impaired. Review of the published cases supports this contention. Normal platelet survival, normal total circulating platelet mass, and intrinsically normal platelet function suggest that the giant platelets and the thrombocytopenia result from impaired and disorderly megakaryocyte fragmentation.