Acquired platelet dysfunction with eosinophilia

Idiopathic Purpura With Gray Platelets: an Acquired Form of Gray Platelet Syndrome

An acquired, transient bleeding disorder that predominantly affects children in Southeast Asia has been reported for the last 4 decades. The condition has been named idiopathic purpura with gray platelets (IPGP) or acquired platelet dysfunction with eosinophilia. In a retrospective review from a private pediatric clinic over an 8-year period, 10 consecutive children were diagnosed as IPGP with a mean age of 8.4 (3.7 to 16.2) years. Eosinophilia (>0.5×10/L) was absent in 1, while gray platelets were consistently found in all cases with a mean proportion of 64.5% (40% to 80%). Platelet aggregation tests were performed in 9 patients with abnormal responses consistent with platelet storage pool defect. All children recovered completely and spontaneously from 1 to 4 months after diagnosis without specific therapy. In an otherwise well child who presents abruptly with easy bruising and a platelet count >100×10/L, IPGP can be readily recognized as an acquired form of gray platelet syndrome. Eosinophilia is common but not mandatory for diagnosis.

Inhibition of human platelet aggregation by eosinophils

AIMS

The relationship between the activity of eosinophils and platelets has been observed in recent decades by many scientists. These observations include increased numbers of eosinophils associated with platelet disorders, including changes in the coagulation cascade and platelet aggregation. Based on these observations, the interaction between eosinophils and platelets in platelet aggregation was analyze.

MAIN METHODS

Human platelets were incubated with eosinophil cytosolic fraction, promyelocytic human HL-60 clone 15 cell lineage, and eosinophil cationic protein (ECP). Platelet rich plasma (PRP) aggregation was induced by adenosine diphosphate, platelet activating factor, arachidonic acid, and collagen, and washed platelets (WP) were activated by thrombin.

KEY FINDINGS

Aggregation induced by all agonists was dose dependently inhibited by eosinophil cytosolic fraction. This inhibition was only partially reversed by previous incubation of the eosinophils with l-Nitro-Arginine-Methyl-Ester (l-NAME). Previous incubation with indomethacin did not prevent the cytosolic fraction induced inhibition. The separation of eosinophil cytosolic fraction by gel filtration on Sephadex G-75 showed that the inhibitory activity was concentrated in the lower molecular weight fraction. HL-60 clone 15 cells differentiated into eosinophils for 5 and 7 day were able to inhibit platelet aggregation. The ECP protein inhibited the platelet aggregation on PRP and WP. This inhibition was more evident in WP, and the citotoxicity MTT assay proved the viability of tested platelets, showing that the observed inhibition by the ECP protein does not occur simply by cell death.

SIGNIFICANCE

Our results indicate that eosinophils play a fundamental role in platelet aggregation inhibition.

Unusual hematologic disease affecting Caucasian children traveling to Southeast Asia: acquired platelet dysfunction with eosinophilia

An 11-year-old American boy was staying with his family in Indonesia. He presented with a 5-month history of recurrent bruises and ecchymosis. A clinical diagnosis of acquired platelet dysfunction with eosinophilia was made when his full blood counts showed hypereosinophilia (7.4×10(9)/L) with normal platelet count and gray platelets under the microscope. The diagnosis was supported by abnormal platelet aggregation tests consistent with a storage pool disorder. The bleeding symptoms and eosinophilia resolved a month later with a full course of antihelminthic therapy. Hematologists should be aware of this unusual disease in travelers returning from the Southeast Asia.

Acquired platelet dysfunction with eosinophilia in white children

Acquired platelet dysfunction associated with eosinophilia has been described mainly in indigenous Southeast Asian and East Indian children. We describe two white boys in whom this disorder developed after they had lived in Malaysia for 12 to 18 months. Acquired platelet dysfunction associated with eosinophilia should therefore be considered in children who, after a visit to this region, have easy bruising and esoinophilia.