Platelet refractoriness to classical agonists in a child with essential thrombocythemia.

BACKGROUND

Essential thrombocythemia is a rare disease during childhood. Platelet morphological abnormalities are frequent and defects in platelet function tests, mainly hypoaggregation, occur.

MATERIALS AND

METHODS

An incidental diagnosis of essential thrombocythemia was established in a 9-year-old boy with a platelet count of 2050 x 10(9)/l. His platelets were studied for aggregation defects with four classical agonists employing optical aggregometry.

RESULTS

Aggregation ranged from 5% for adrenaline, 8% for collagen, 12% for ristocetin, to 25% with adenosine diphosphate, followed by complete disaggregation.

CONCLUSION

Platelet refractoriness to classical agonists, probably compounded by platelet GPIb deficiency, was documented. The differential diagnosis is discussed.