- Clonal hematopoiesis of indeterminate potential (CHIP): the presence of somatic mutations in leukemia driver genes at a VAF of ≥ 2% without meeting the criteria for hematologic malignancy.
- CHIP is associated with a 0.5% to 1% annual risk of progression to hematologic malignancy and increases the risk of cardiovascular events due to a proinflammatory state.
- Clonal cytopenia of undetermined significance (CCUS): the combination of unexplained cytopenia(s) and somatic mutations without marrow dysplasia or other diagnostic criteria for hematologic malignancies.
- CCUS carries a higher risk of progression to myeloid neoplasms compared to CHIP, particularly in cases featuring high-risk mutations.
- Idiopathic cytopenia of undetermined significance (ICUS): the presence of one or more cytopenias with no identifiable mutation or other cause.
Presentation
- Patients with CHIP are often asymptomatic and identified incidentally during genetic testing.
- CCUS patients present with unexplained cytopenias but do not meet criteria for MDS or other hematologic malignancies.
- CHIP and CCUS are associated with an increased risk of progression to myeloid neoplasms and non-hematologic complications such as cardiovascular disease (atherosclerosis, myocardial infarction and stroke) and renal disease.
- Clinical pearl: consider CH-related disorders in patients with premature or unexplained cardiovascular disease, as the inflammatory effects of clonal hematopoiesis can accelerate atherosclerosis independent of traditional risk factors.
Evaluation
- Routine screening with next-generation sequencing (NGS) is not currently recommended for asymptomatic individuals.
- Genetic testing may be considered in patients with unexplained cytopenias or during the evaluation for other hematologic conditions.
- Screening for CH-related disorders typically involves NGS to detect somatic mutations in genes such as DNMT3A, TET2, and ASXL1.
- Additional tests may include cytogenetic analysis and flow cytometry to rule out other hematologic malignancies.
- Risk calculators, such as the Clonal Hematopoiesis Risk Score (CHRS), can stratify patients into low, intermediate or high risk.
High-Risk Features for Progression from Clonal Hematopoiesis to Myeloid Neoplasm
Category
|
Risk Factor
|
Significance
|
| Demographics |
Age ≥ 65 years |
Older patients have higher risk of progression |
| Hematologic parameters |
Red cell distribution width ≥ 15% |
Indicates altered erythropoiesis Mean cell volume ≥ 100 femtoliters Macrocytosis suggests |
| Mean cell volume ≥ 100 femtoliters |
Macrocytosis suggests dyserythropoiesis |
| Presence of any cytopenia |
Suggests early bone marrow dysfunction |
| Mutation characteristics |
Variant allele frequency ≥ 20% |
Higher allele frequency suggests greater clonal dominance |
| ≥ 2 mutations in leukemia driver genes |
Multiple mutations indicate more advanced clonal evolution |
| Specific mutations |
Splicing factor mutations (SRSF2, SF3B1, ZRSR2) |
Associated with higher risk of progression to MDS/AML |
| TP53 mutations |
Associated with myeloid neoplasms secondary to cancer treatment and poor outcomes |
| IDH1/2 mutations |
Higher risk of progression to AML |
| Clinical context |
Prior chemotherapy or radiation exposure |
Therapy-related CH has higher progression risk |
| Serial monitoring |
Increasing variant allele frequency over time |
Suggests active clonal expansion |
| Acquisition of new mutations |
Indicates ongoing genomic instability |
Risk Stratification and Prognosis per CHRS
Risk Category
|
Percentage of CH Patients
|
10-Year Risk of Myeloid Neoplasm
|
| Low risk |
90% |
~0.6% |
| Intermediate risk |
9% |
~8% |
| High risk |
1% |
~30% |
Management
- Patients with CH-related disorders should undergo periodic CBC and clinical evaluation; however, there are no current guidelines for the frequency of evaluation.
- Those with CCUS require closer surveillance due to a higher risk of progression to hematologic malignancy.
- Lifestyle modifications and management of cardiovascular risk factors are crucial.
- Currently, there are no FDA-approved therapies for CH-related disorders.
