Beyond the Known: Expanding the Clinical and Genetic Spectrum of Rare RPL13-Related Spondyloepimetaphyseal Dysplasia

Spondyloepimetaphyseal dysplasia type Isidor-Toutain (RPL13-SEMD) is an autosomal dominant skeletal dysplasia caused by heterozygous pathogenic variants in the RPL13 gene, encoding the ribosomal protein eL13. To date, 13 pathogenic variants in RPL13 have been reported, all clustering within intron 5 and exon 6, suggesting this hotspot region is critical for the function of ribosomes in skeletal tissues. Here, we present clinical and radiological characteristics of seven individuals, five children and two adults, from four unrelated families with RPL13-SEMD caused by two novel variants (c.477+5G>C and c.539_541del) and two previously reported variants (c.477+1G>C and c.548G>A) in RPL13. RNA analysis demonstrated that c.477+5G>C leads to a 54-nucleotide extension of exon 5, resulting in an 18-amino acid insertion. The phenotypic spectrum ranged from mild manifestations, such as Blount-like tibial deformity without significant short stature or Perthes-like femoral epiphyseal changes, to severe skeletal deformities with disproportionate short stature, accompanied by extraskeletal features (e.g., penoscrotal hypospadias, coccygeal abnormalities). For the first time, we describe Blount-like tibial deformity as a feature of this dysplasia, which resolves with age. Our study provides additional insights into the clinical, radiological, and genotypic features of RPL13-SEMD through detailed analysis of patients and their affected relatives.