A myeloid disorder that occurs in childhood and is characterized by persistent cytopenia, dysplastic changes in at least two hematopoietic lineages or in 10% or more of cells in one hematopoietic lineage, less than 5% blasts in bone marrow, and less than 2% blasts in peripheral blood, absence of bone marrow fibrosis, and absence of history of prior cytotoxic chemotherapy or radiation therapy. In a subset of cases, somatic mutations or cytogenetic abnormalities can be identified. Other cases are the result of pre-existing disorders with germline mutations, including Fanconi anemia, Shwachman-Diamond syndrome, and dyskeratosis congenita. [from
NCI]