Histopathology of recurrent Steel syndrome in fetuses caused by novel variants of COL27A1 gene.

Steel syndrome (STLS) encompasses characteristic facies, dwarfness, irreducible bilateral hip and radial head dislocation, and carpal bone coalition due to COL27A1 mutations. Two consecutive pregnancies in a non-consanguineous couple were terminated because of severe fetal anomalies. Complete autopsies with microscopic exam were performed on both fetuses. Next-generation-based clinical exome sequencing was applied to the first fetus. Exome sequencing results, parental segregation, and affection of the second fetus were confirmed by Sanger sequencing. Both fetuses had signs consistent with STLS. Bilateral capitulum humeri absence explained radial head dislocation in STLS. Metaphyseal cartilage showed severe disorganization. Resting cartilage was hypercellular, organized in irregular nests limited by acellular matrix. Two variants in COL27A1 (c.2548G>A -p.Gly850Arg- and c.3249+1G> T) were found in both fetuses in compound heterozygosity with parental Mendelian segregation. This is the first report to include histology of STLS. The COL27A1 variants here described increase the number of mutations associated with STLS.