Diagnosing platelet δ-storage pool disease in children by flow cytometry

Bleeding problems are symptomatic of platelet delta-storage pool diseases (SPDs) such as Hermansky-Pudlak syndrome. Although at present no cure is available for delta-SPD, early diagnosis is of great importance for prophylactic and supportive treatment. This study tested the usefulness of a flow cytometric assay for platelet serotonin in children. The assay was used to diagnose delta-SPD in a 10-year-old girl. Platelet serotonin levels were significantly lower in the patient than in all healthy control subjects (10 children and 10 adults). The serotonin results were supported by traditional tests, which are transmission electron microscopy of whole mounts and adenosine triphosphate release by lumi-aggregometry. The flow cytometric serotonin assay is a major improvement to current pediatric diagnostics. The advantages of this test are small sample volume of fresh or fixed/frozen platelets, availability of objective results within 2 hours of obtaining the blood sample, and automated analysis by flow cytometry.