Reddy K S, Logan J J
Cytogenetics Department, Quest Diagnostics Inc, San Juan Capistrano, CA 92690, USA.
Clin Genet. 2000 Aug;58(2):134-41. doi: 10.1034/j.1399-0004.2000.580208.x.
A newborn boy had meconium aspiration syndrome, hypospadias, a supernumerary digit on the left hand, hyperbilirubinemia, a fractured right clavicle, osteopenia, liver calcification, and mild pulmonary hyperplasia. Cytogenetic studies showed a chromosome 13 with additional material in 33% of the metaphases. The add(13) was considered to be a probable duplication of 13q12q22. The 13 paint probe hybridized to the add(13) from end to end. Fluorescence in situ hybridization (FISH) studies using retinoblastoma probe (RB)-1 that maps to 13q14 and D13S585 that maps to 13q32-q33 gave one signal for RB and three signals for D13S585. The pattern of the three signals from the 13q32q33 region and the G-banding pattern was best explained as a triplication of 13q22q33, with an inverted middle repeat resulting in tetrasomy for this segment. Mosaicism was confirmed by FISH using a D13S585 probe on a buccal smear. Three triplications detected in our laboratory were compared 13q22q33, 15q11q13, and 2q11.2q21. FISH was critical in identifying triplications 13q22q33 and 15q11q13. The hybridization pattern also indicated an inverted middle repeat. We conclude that intrachromosomal triplications may be more prevalent than previously assumed and they probably share a common mechanism in their formation. When the G-bands do not correspond exactly to a duplication or to a tandem triplication, an important consideration is that the majority of triplications have an inverted middle repeat. Triplications can be mistaken for duplications. Therefore, in assessing duplications, FISH confirmation is recommended.
一名男婴患有胎粪吸入综合征、尿道下裂、左手多指、高胆红素血症、右锁骨骨折、骨质减少、肝脏钙化和轻度肺增生。细胞遗传学研究显示，在33%的中期相中，13号染色体存在额外物质。add(13)被认为可能是13q12q22的重复。13号染色体涂染探针从头到尾与add(13)杂交。使用定位于13q14的视网膜母细胞瘤探针(RB)-1和定位于13q32-q33的D13S585进行荧光原位杂交(FISH)研究，结果显示RB为一个信号，D13S585为三个信号。来自13q32q33区域的三个信号模式和G带模式最好解释为13q22q33的三重重复，中间重复序列倒置导致该片段出现四体性。通过在颊黏膜涂片上使用D13S585探针进行FISH证实了嵌合体现象。将我们实验室检测到的三个三重重复（13q22q33、15q11q13和2q11.2q21）进行了比较。FISH对于识别13q22q33和15q11q13的三重重复至关重要。杂交模式也表明存在中间重复序列倒置。我们得出结论，染色体内三重重复可能比以前认为的更为普遍，并且它们在形成过程中可能共享一种共同机制。当G带与重复或串联三重重复不完全对应时，一个重要的考虑因素是，大多数三重重复都有中间重复序列倒置。三重重复可能会被误认为是重复。因此，在评估重复时，建议进行FISH确认。
