Novel Heritable Mutation of the Transcription Factor RUNX1 as a Cause of Autosomal Dominant Familial Platelet Disorder with Predisposition to Acute Myeloid Leukemia (FPD/AML).

Aim To identify the causative heritable mutation in a family with autosomal dominant familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML).

Method Confirmation of family pedigree, enrolment into ethics committee approved Australian Familial Hematological Cancer Study, procurement of genomic DNA from pedigree members and genetic analysis by sequencing of RUNX1 and CEBPA genes.

Results The proband intially presented aged 50 with mild thrombocytopenia initially diagnosed as idiopathic thrombocytopenic purpura when bone marrow examination (including cytogenetics analysis) was normal. Three years later she was referred with severe progressive thrombocytopenia unresponsive to high dose steroids and intravenous immunoglobulin together with mild anemia and neutropenia. Marrow examination revealed subtle dysplasia with monosomy 7 in 12/20 metaphases. A diagnosis of myelodysplastic syndrome (MDS) was made. Three months later (Feb 2007), she progressed to acute myeloid leukemia (AML). The proband’s mother had had mild thrombocytopenia with subsequent MDS (aged 70) and died of AML two years later. The proband’s only sibling and nephew have mild thrombocytopenia without features of MDS. The proband entered cytogenetic remission following one course of AML induction therapy but continued to show dysplastic features. She then received 2 cycles of consolidation therapy and has undergone unrelated donor allogeneic stem cell transplant (July 2007). Sequencing of PCR products from exons of the RUNX1 gene identified a novel heterozygous mutation in the proband’s constitutional DNA: c.958C>T in exon 7, in the transactivation domain, causing a nonsense mutation, p.Arg293X (sequence variation for RUNX1 classified according to GenBank Accession No. NC_000021). The sibling has the same mutation and studies in other relatives are underway.

Conclusion This study has identified a novel RUNX1 mutation responsible for FPD/AML in this family. Clinicians should be aware of this rare inherited disorder and the availability of genetic testing. People with mutations may be asymptomatic and genetic testing in such families is essential before considering bone marrow transplantation from a living related donor.