Clonal hematopoiesis in patients with autoimmune thrombocytopenia: an international multicenter study

• 18.5% of 167 ITP patients had somatic mutations typical of clonal hemopoiesis, 68% had high-risk variants, and 8 multiple mutations

• Mutated patients were more frequently elderly males, with a shorter time from first to second line therapy, and had a higher thrombotic risk

Diagnostic boundaries between immune thrombocytopenia (ITP) and other thrombocytopenic states such as thrombocytopenic myelodysplastic syndromes, may be difficult to establish, and the detection of somatic mutations by next generation sequencing (NGS) may be of aid. Here we aimed at characterizing the prevalence and clinical significance of clonal hematopoiesis in ITP. In this multicentric retrospective observational study we enrolled 167 adult ITP patients, followed at 13 centers in Italy, UK, and USA. Patients underwent NGS evaluation after a median of 3.6 years from ITP onset and 83% had received at least one therapy line, median 2 (0-9) lines; 51 out of 167 patients had at least one mutation (30%). After exclusion of germline variants and polymorphisms, 18.5% (31/167) were defined as having clonal hemopoiesis. Most commonly mutated genes were TET2, DNMT3A, SRSF2, and ASXL1 (median VAF 29%); 19 of 31 subjects (68%) had high-risk variants, and 8 multiple mutations. Mutated patients were more frequently elderly males and showed a shorter time from first to second line therapy, particularly with TPO-RA. Additionally, clonal hematopoiesis was associated with increased thrombotic risk (26% vs 8% in NGS-negative cases, p=0.01), independently from TPO-RA exposure, though with an age effect. These data demonstrated the prevalence of clonal hematopoiesis in 18% of adult ITP patients, being associated with older age, relapsed/refractory disease, and high risk of thrombotic complications.