Age-dependent changes in platelet function of a patient with <i>SLFN14</i>-related macrothrombocytopenia

Platelet-type bleeding disorder-20 is a rare inherited thrombocytopenia caused by mutations in the SLFN14 gene. We report a case of a female patient with SLFN14 mutation, macrothrombocytopenia, severe hemorrhagic syndrome and a positive family history who was followed up from the age of 17 to 19. The 3-year follow-up showed a tendency towards partial normalization of platelet counts (from 47 to 82 × 109/L) and morphology. Platelet size and granularity as well as the density of glycoprotein (GP) membrane receptors such as GP Ib/V/IX and GP IIb/IIIa decreased. GP IIb/IIIa activation was impaired and there were no positive changes over time. The dense granules indicators were stably elevated. The parameters of a-granules (assessed by P-selectin expression) did not differ from the control group. The proportion of procoagulant phosphatidylserine-positive platelets at rest was increased and the potential to form procoagulant platelets upon activation was reduced. As the patient grew older, her bleeding disorder symptoms abated and she showed a tendency towards normalization of platelet laboratory parameters. All investigations were performed after obtaining informed consent from the patient and her parents in accordance with the Declaration of Helsinki.