Ehlers-Danlos syndrome kyphoscoliotic type 2 caused by mutations in the FKBP14 gene: an analysis of five cases.

Background. This study deals with a rare (orphan) monogenic connective tissue disorder - Ehlers-Danlos syndrome kyphoscoliotic type 2 (EDSKS2). Kyphoscoliotic type 2 Ehlers-Danlos syndrome is an autosomal recessive disorder caused by mutations in the FKBP14 gene (7p14.3), which encodes the FKBP22 protein. According to the 2017 classification, this type is in group seven - collagen spatial structure and cross-linking defects. We present results of clinical examination and molecular genetic analysis for five patients with age varying from two to fifteen years.  Methods. Five patients were examined using clinical and laboratory methods. DNA samples used for the analysis were extracted from whole blood samples using a Wizard® Genomic DNA Purification Kit (Promega, USA) according to the manufacturer's protocol.  Results. The major clinical findings were kyphoscoliosis, early motor development delay, muscular weakness, hypotonia and hearing loss. Molecular genetic analysis detected a homozygous c.362dupC duplication in exon 3 of the FKBP14 gene in all five patients. This mutation is common in various countries. Differential diagnostics were carried out to exclude other Ehlers-Danlos syndrome types and myopathies.  Conclusions. Literature analysis and examination of five EDSKS2 patients demonstrated the involvement of major organs and systems, such as joints, spine, muscles, cardiovascular system, respiratory system, hearing, and vision, into the pathological process. Kidney mobility increases and nephroptosis seems to be secondary caused by muscular weakness. During molecular genetic analysis, to verify EDSKS2 it is recommended to initially search for the c.362dupC duplication, which appears to be common in European countries, including Russia.