Chronic Myelomonocytic Leukemia in a Patient With a Germline Predisposition and Short Telomeres

Myeloid neoplasms with germline predisposition are an increasingly recognized category within the World Health Organization classification. Detection requires a high degree of suspicion, with mounting awareness of clinically silent phenotypes and heterogeneous presentations, challenging diagnostic and laboratory testing considerations, need for surveillance of disease progression, and unique concerns in donor selection for stem cell transplantation. We describe the case of a patient who presented as a teenager with thrombocytopenia and was later diagnosed with chronic myelomonocytic leukemia, with eventual transformation to acute myeloid leukemia, which has relapsed after stem cell transplantation. She was found to have short telomeres and a TERTmutation, in addition to numerous features suggestive of a germline predisposition syndrome. These findings have not been specifically associated with chronic myelomonocytic leukemia and raise interesting questions about the associations between myelodysplastic/myeloproliferative neoplasms, telomere biology disorders, and the roles of specific myeloid mutations as drivers of disease.