Small supernumerary marker chromosomes (sSMCs) are characterized as additional centric chromosome fragments which are too small to be classified by cytogenetic banding alone and smaller than or equal to the size of chromosome 20 of the same metaphase spread. Here, we report a patient who presented with slight neutropenia and oral aphthous ulcers. A mosaic de novo sSMC, which originated from 5 discontinuous regions of chromosome 8, was detected in the patient. Formation of the sSMC(8) can probably be explained by a multi-step process beginning with maternal meiotic nondisjunction, followed by post-zygotic anaphase lag, and resulting in chromothripsis. Chromothripsis is a chromosomal rearrangement which occurs by breakage of one or more chromosomes leading to a fusion of surviving chromosome pieces. This case is a good example for emphasizing the importance of conventional karyotyping from PHA-induced peripheral blood lymphocytes and examining tissues other than bone marrow in patients with inconsistent genotype and phenotype.

中文翻译：

---

来自一名中性粒细胞减少症和口腔阿弗他溃疡患者的 8 号染色体的五个不连续区域的镶嵌小额外标记染色体

小的多余标记染色体 (sSMCs) 的特征是额外的中心染色体片段，这些片段太小而无法单独通过细胞遗传显带进行分类，并且小于或等于相同中期分布的 20 号染色体的大小。在这里，我们报告了一名出现轻度中性粒细胞减少和口腔阿弗他溃疡的患者。在患者中检测到源自 8 号染色体的 5 个不连续区域的嵌合体 de novo sSMC。sSMC(8) 的形成可能可以通过一个多步骤过程来解释，从母体减数分裂不分离开始，然后是合子后后期滞后，并导致染色体碎裂。Chromothripsis 是一种染色体重排，由一条或多条染色体断裂导致幸存的染色体片段融合而发生。