Novel RUNX1 Mutation in a Family with an Uncharacterized Secretion Defect

• Published in: Blood 2015-12, Vol.126 (23), p.3458-3458
• Main Authors: Badin, M., Hayward, C. P.M., Tasneem, S., Pare, G., Paterson, A.D., Waye, J.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V126.23.3458.3458

Background: Platelet function disorders are a common cause of a bleeding problem. While many rare and severe forms of platelet function disorders are well studied, many common platelet function defects are uncharacterized. In a family with uncharacterized platelet secretion defects, we identified a single base pair insertion in the gene RUNX1 by exome sequencing. We report on the clinical and laboratory phenotype of the defect in this family. Methods: Bleeding histories of affected and unaffected family members, obtained using a standardized questionnaire, were scored using the International Society on Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH BAT). Laboratory data evaluated included blood counts, platelet aggregation responses, dense granule ATP release findings (lumiaggregometry) and platelet dense granule counts, evauated by whole mount preparations and electron microscopy. Affection status was based on the recorded opinion of the subject's hematologist, which concurred with diagnostic laboratory findings. Exome sequencing was performed on the index case, followed by evaluation of all family members for the candidate mutation by polymerase chain reaction (PCR) amplification and Sanger sequencing. Results: Family members investigated (median age: 25.5, range 1-69] included 5 males (affected: n=4, unaffected: n=1) and 3 females (affected: n=2, unaffected: n=1). ISTH BAT bleeding scores for affected members were elevated (median: 10.5, range 4-20), unlike unaffected family members (n=2) and healthy controls (n=40) (ranges: 0-1 and 0-2). Platelet counts were low in 2/6 affected individuals (109 platelets/L : affecteds: median: 164, range: 125-169). While unaffected family members had unremarkable platelet function findings, the affected individuals had absent or reduced dense granule secretion with all agonists tested (including thrombin, collagen, epinephrine, U46619 and arachidonic acid), and in aggregation tests, they had absent secondary aggregation with epinephrine, reduced maximal aggregation with collagen (1.25 and 5.0 μg/mL) and thromboxane analogue U46619, variable responses to arachidonic acid (reduced in 4/5 affecteds), and normal responses to ADP and ristocetin. Only some (3/6) affected family members had dense granule deficiency (lower reference interval limit: 4.9/platelet; affecteds: median: 5.2, range: 4-6). A single base pair insertion (A) in exon 6 of the RUNX1 gene (NM_001754.4:c.583dup) was identified in the index case us