Accurate interpretation of genomic copy number variation (CNV) remains a challenge and has important consequences for both congenital and late-onset disease. Hemizygosity dosage characterization of the genes on chromosome 18 reveals a spectrum of outcomes ranging from no clinical effect, to risk factors for disease, to both low- and high-penetrance disease. These data are important for accurate and predictive clinical management. Additionally, the potential mechanisms of reduced penetrance due to dosage compensation are discussed as a key to understanding avenues for potential treatment. This review describes the chromosome 18 findings, and discusses the molecular mechanisms that allow haploinsufficiency, reduced penetrance, and dosage compensation.

对基因组拷贝数变异（CNV）的准确解释仍然是一个挑战，对先天性疾病和迟发性疾病都有重要影响。18号染色体上基因的半合子剂量表征揭示了一系列结果，从无临床效果到疾病的危险因素，再到低穿透性和高穿透性疾病。这些数据对于准确和预测性的临床管理非常重要。此外，讨论了由于剂量补偿而导致的外et减少的潜在机制，这是了解潜在治疗途径的关键。这篇综述描述了第18号染色体的发现，并讨论了允许单倍剂量不足，渗透率降低和剂量补偿的分子机制。