Skeletal ciliopathies are a heterogenous group of disorders with overlapping clinical and radiographic features including bone dysplasia and internal abnormalities. To date, pathogenic variants in at least 30 genes, coding for different structural cilia proteins, are reported to cause skeletal ciliopathies. Here, we summarize genetic and phenotypic features of 34 affected individuals from 29 families with skeletal ciliopathies. Molecular diagnostic testing was performed using massively parallel sequencing (MPS) in combination with copy number variant (CNV) analyses and in silico filtering for variants in known skeletal ciliopathy genes. We identified biallelic disease-causing variants in seven genes: DYNC2H1, KIAA0753, WDR19, C2CD3, TTC21B, EVC, and EVC2. Four variants located in non-canonical splice sites of DYNC2H1, EVC, and KIAA0753 led to aberrant splicing that was shown by sequencing of cDNA. Furthermore, CNV analyses showed an intragenic deletion of DYNC2H1 in one individual and a 6.7 Mb de novo deletion on chromosome 1q24q25 in another. In five unsolved cases, MPS was performed in family setting. In one proband we identified a de novo variant in PRKACA and in another we found a homozygous intragenic deletion of IFT74, removing the first coding exon and leading to expression of a shorter message predicted to result in loss of 40 amino acids at the N-terminus. These findings establish IFT74 as a new skeletal ciliopathy gene. In conclusion, combined single nucleotide variant, CNV and cDNA analyses lead to a high yield of genetic diagnoses (90%) in a cohort of patients with skeletal ciliopathies.

纤毛骨骼病是一组异质性疾病，具有重叠的临床和影像学特征，包括骨发育不良和内部异常。迄今为止，据报道，编码不同结构纤毛蛋白的至少 30 个基因中的致病变异会导致骨骼纤毛病。在这里，我们总结了来自 29 个骨骼纤毛病家族的 34 名受影响个体的遗传和表型特征。分子诊断测试是使用大规模平行测序 (MPS) 结合拷贝数变异 (CNV) 分析和计算机过滤已知骨骼纤毛病基因中的变异进行的。我们在七个基因中鉴定了双等位基因致病变异：DYNC2H1、KIAA0753、WDR19、C2CD3、TTC21B、EVC和EVC2。位于DYNC2H1、EVC和KIAA0753的非规范剪接位点的四个变体导致异常剪接，这通过 cDNA 的测序显示。此外，CNV 分析显示一个个体的DYNC2H1基因内缺失和另一个个体染色体 1q24q25 上的 6.7 Mb 从头缺失。在五个未解决的案例中，在家庭环境中进行了 MPS。在一个先证者中，我们发现了PRKACA中的从头变异，在另一个先证者中，我们发现了IFT74的纯合基因内缺失，去除第一个编码外显子并导致更短的信息的表达，预计会导致 N 末端 40 个氨基酸的丢失。这些发现将IFT74确立为一种新的骨骼纤毛病基因。总之，结合单核苷酸变异、CNV 和 cDNA 分析可在一组患有骨骼纤毛病的患者中获得高产量的基因诊断 (90%)。