New variants in COL5A1 gene among Polish patients with Ehlers-Danlos syndrome – analysis of nine cases

Introduction
The Ehlers-Danlos syndrome (EDS) is a non-inflammatory, heritable connective tissue disorder divided into 13 types according to the 2017 International Classification of the Ehlers-Danlos syndromes. One of the subtypes of EDS, classical (cEDS), is characterized by joint hypermobility, skin hyperextensibility and atrophic scars, which are major criteria of cEDS.

Aim
In this study, the first in Central Eastern Europe, 44 patients were investigated. All of them were tested for COL5A1 mutations with direct DNA sequencing.

Material and methods
The study group included 44 patients of Polish origin, all of whom fulfilled criteria for the classical type of Ehlers-Danlos syndrome. Direct sequencing of the COL5A1, COL5A2 and COL1A1 c.934C>T genes was performed for all of them. Evaluation of potential pathogenicity of detected missense mutation was conducted using SIFT (Sorting Intolerant from Tolerant), PolyPhen-2, AlignGVGD (Align Grantham Variance/Grantham Difference). The effect of the splice site mutations was predicted by Human Splicing Finder and NetGene2 tools.

Results
Among all tested patients, nine mutations of COL5A1 gene were detected (8 missense mutations and 1 splice site). The alterations identified by us are new, hitherto not described in other reports. Evaluation of the mutations by in silico tools indicate their pathogenicity.

Conclusions
Our study is the first COL5A1 gene molecular investigation conducted among cEDS patients from Central Eastern Europe. Besides new COL5A1 variant findings, we gained molecular confirmation of clinical diagnosis of cEDS. In some cases, specific and adequate evaluation and classification of EDS patients based only on clinical features, may be difficult.