Platelet studies in the pathogenesis of thrombocytopenia in May-Hegglin anomaly

Thrombocytopenia has a variable incidence in the May-Hegglin anomaly, a rare congenital syndrome characterized by inclusions resembling Dohle bodies within leukocytes, thrombocytopenia, and giant platelets. We studied a 16-year-old girl and three relatives with the syndrome to elucidate the pathogenesis of the thrombocytopenia and the degree of impaired hemostasis. On confirmation of automated platelet counts by manual techniques we found that both aperture-impedence and light-scatter instruments tended to undercount the actual number of platelets by 30–50%. An enzyme immunoassay for platelet-associated IgG showed elevated levels in all patients (mean of 2.3 ± 0.6 ng/10⁶ platelets versus 0.8 ± 0.6 in normals, p < 0.0001). Bleeding time and platelet aggregation in response to adenosine diphosphate, arachidonic acid, epinephrine, ristocetin, and collagen were all normal. No clinical bleeding was observed in any of the patients in the face of major surgery or childbirth. The findings suggest the possibility of a peripheral destructive and perhaps an immune pathogenesis of the thrombocytopenia of May-Hegglin anomaly and confirm that clinical bleeding may not accompany the severe thrombocytopenia seen in this disorder.