Genetic predispositions to myeloid malignancies can be classified into three categories: familial cancer syndromes associated with increased risk of various malignancies including myelodysplasia and acute myeloid leukemia such as Li-Fraumeni syndrome and constitutional mismatch repair deficiency (CMMRD); germline mutations conferring a specific increased risk of myelodysplastic syndrome and acute myeloid leukemia such as mutations in ANKRD26, CEBPA, DDX41, ETV6, GATA2, RUNX1, SRP72 genes; and finally primarily pediatric inherited bone marrow failure syndromes such as Fanconi anemia, dyskeratosis congenita, severe congenital neutropenia, Shwachman-Diamond syndrome and Diamond Blackfan anemia.
Because L-leucine can be used to treat Diamond-Blackfan anemia, which is caused by defects in ribosomal protein (RP) genes, resulting in increased in vivo hemoglobin synthesis, it is possible that some MDS patients who have aberrations in their RP genes could also be effectively treated with L-leucine.
Among 175 patients included, the majority had sickle cell disease (SCD; 52%), followed by aplastic anemia (AA; 17.7%), myelodysplastic syndrome (MDS; 8.6%), Diamond-Blackfan anemia (DBA; 4%), pure red cell aplasia (1.1%), and others (16.6%).
Bone marrow failure syndromes have been well-described in the pediatric setting, e.g., Fanconi anemia (FA), dyskeratosis congenita (DC), Diamond-Blackfan anemia (DBA), and Shwachman-Diamond syndrome (SBS), hallmarked by clinically-recognizable phenotypes (e.g., radial ray anomalies in FA) and significantly increased risks for MDS and/or acute myeloid leukemia (AML) in the setting of bone marrow failure.
The most common of these rare disorders include Fanconi anemia, dyskeratosis congenita, Shwachman-Diamond syndrome and amegakaryocytic thrombocytopenia, which often develop aplastic anemia and may evolve into myelodysplastic syndrome and acute myeloid leukemia; and Diamond-Blackfan anemia, severe congenital neutropenia, and thrombocytopenia absent radii, single cytopenias that rarely if ever become aplastic but have increased risks of leukemia.