Early Development of the First Bulgarian Patient With Steel Syndrome

Steel syndrome (MIM# 615155) is a rare autosomal recessive skeletal dysplasia caused by biallelic pathogenic variants in the COL27A1 gene. It is characterized by congenital bilateral hip dislocation, radial head dislocation, scoliosis, short stature, and distinctive craniofacial features. Most cases have been reported in the Puerto Rican population, with only a few genetically confirmed cases worldwide.

Case presentation: We report the first clinically and molecularly confirmed case of Steel syndrome in Bulgaria – a child presenting from birth with multiple skeletal anomalies, including bilateral hip dysplasia, thoracolumbar scoliosis, knee contractures, and craniofacial dysmorphism. Whole-exome sequencing identified a novel homozygous frameshift variant in COL27A1: c.420delG (p.Ser141Profs*31), classified as likely pathogenic according to ACMG criteria.

Conclusion: This case expands the mutational and geographic spectrum of COL27A1-related disorders and highlights the importance of early genetic diagnosis for guiding multidisciplinary care. Conservative treatment remains the preferred strategy, given the poor surgical outcomes described in previous reports. This represents the first reported in Bulgaria and only the second European case of Steel syndrome.