Familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML) has been well documented in the literature and is a new entity within the latest revised edition of the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues (OMIM). The disorder arises due to mutations within the RUNX1 gene in chromosome 21; mutations within the Runt-binding domain are the most commonly encountered anomalies that cause decreased platelet count and function. Rare cases of haploinsufficiency have also been shown to cause this disorder. Here, we describe a 12-year-old female with mosaicism for a ring chromosome 21 and monosomy 21 who was born with thrombocytopenia which is now explained by loss of the RUNX1 gene resulting in FPD/AML. We also comment on the structure of the ring and the mechanism of its formation.

中文翻译：

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血小板减少症和因失去RUNX1的Mosaic环21而导致的急性髓细胞性白血病的易感性：细胞遗传学和分子表征。

易患急性髓细胞性白血病（FPD / AML）的家族性血小板疾病在文献中已有充分文献记载，并且是WHO造血和淋巴组织肿瘤分类（OMIM）最新修订版中的一个新实体。这种疾病是由于21号染色体中RUNX1基因内的突变引起的。Runt结合域内的突变是最常见的异常现象，会导致血小板计数和功能下降。单倍机能不全的罕见病例也已被证明可引起这种疾病。在这里，我们描述了一位12岁的女性，她患有21岁以下的环状染色体和21号染色体的拼接症，该患者出生于血小板减少症，现在可通过导致FPD / AML的RUNX1基因缺失来解释。我们还评论了环的结构及其形成机理。