First reported case of Steel syndrome in the European population: A novel homozygous mutation in COL27A1 and review of the literature.

Steel syndrome is an autosomal recessive disorder that primarily affects the skeletal system causing a variety of manifestations. Sixteen individuals with Steel syndrome, mainly Puerto Ricans (11/16), were previously reported to carry bi-allelic mutations in the COL27A1 gene. Here, we present the first patient with Steel syndrome in Europe and the sixth non-Puerto Rican carrying a novel homozygous mutation in COL27A1. The patient is a 4-year-old boy born to non-consanguineous healthy parents, with dysmorphic facial features, absent hip ossification centres, external rotation of both feet, relatively short stature, mild skin syndactyly, short mid phalanges and bilateral sensorineural hearing loss. Whole exome sequencing (WES) revealed a novel homozygous missense variant p.(Gly802Glu) in COL27A1. The homozygous mutation was confirmed by Sanger sequencing in the proband and carrier status was confirmed in both parents and his unaffected sibling. According to online and in-house minor allele frequency (MAF) databases, this is the first COL27A1 mutation reported in the European population. Additional screening of healthy Greek-Cypriot individuals was thus performed, which did not reveal any additional carriers in the population for the variant in question.