Abstract
A 25-year-old female underwent emergent laparoscopic salpingectomy when she presented with an ectopic pregnancy (G1P0). A bone marrow biopsy performed for moderate persistent thrombocytopenia (60-105 K/μL) showed normocellularity, maturing trilineage hematopoiesis, and mildly increased morphologically normal megakaryocytes reported as consistent with idiopathic thrombocytopenic purpura (ITP). However, on further inquiry, the patient stated that her sister, father, paternal aunt, and paternal grandfather have/had low platelets. Her father had been diagnosed with myelodysplasia (MDS). Her paternal grandmother had died of acute myeloid leukemia (AML). Thus, although her marrow morphology revealed no evidence of overt dysplasia and despite her normal karyotypic study, a sample was sent for RUNX1 sequence analysis. A splice site mutation (c.967 + 2_967 + 5delTAAG) in RUNX1 was detected and initially interpreted as a somatic mutation. However, given the strong family history of thrombocytopenia and MDS/AML, a sample from her father was also sent for RUNX1 sequence analysis, and the identical intronic sequence variant in the RUNX1 gene was detected in him. This confirmed the RUNX1 mutation to be germline. In the context of autosomal dominant thrombocytopenia in the patient’s family, the finding of this variant in the affected patient and her similarly affected father was consistent with a pathogenic role. Since this patient was of reproductive age actively trying to have children, these molecular genetic findings had important implications. She elected to undergo in vitro fertilization in order to choose embryos without the RUNX1 mutation for implantation. Considering that her father and paternal grandmother developed MDS/AML, and because familial platelet disorder with predisposition to AML appears to show “anticipation,” she would require close future monitoring for blastic transformation. This case illustrates the significance of careful history taking and high suspicion index that can lead to simplified targeted cost-effective molecular testing resulting in the correct diagnosis without necessarily employing large gene panels.
Targeted next-generation sequencing of familial platelet disorder with predisposition to acute myeloid leukaemia
