Case report: Characterization of a rare pathogenic variant associated with loss of COL3A1 expression in vascular Ehlers Danlos syndrome

Abstract

The vascular subtype of Ehlers Danlos Syndrome (vEDS) is a rare connective tissue disorder characterized by spontaneous arterial, bowel or organ rupture. The diagnosis of vEDS is established in a proband by identification of a heterozygous pathogenic variant in the alpha-1 gene of type III collagen (COL3A1) by molecular analysis. In this report, we present a case of vEDS with life threatening, spontaneous arterial dissections in association with an uncharacterized rare variant of COL3A1, exon19:c.1340G > A. Primary culture of patient skin fibroblasts followed by immunofluorescence revealed a complete absence of COL3A1 protein expression as well as altered morphology. Electron microscopy of the cultured fibroblasts showed abnormal vacuoles in the cytoplasm suggestive of a secretory defect. In this study, we have performed functional characterization of the COL3A1 exon19:c.1340G > A variant for the first time and this may now be classified as likely pathogenic in vEDS. *Both JM and LRL contributed equally in the manuscript and should both be considered as the first author.

Keywords: COL3A1 pathogenic variant; clinical fibroblast testing; exome sequencing; hepatic artery dissection; stroke; vascular Ehlers Danlos syndrome.

FIGURE 1

Observed clinical features of the patient, (A): Thin Nose, lobe less ear (red arrow), thin skin with visible chest veins (white arrow), (B): Acrogeria (red arrow) with club foot (white arrow), (C): Easy bruising and thin skin, varicose veins, (D): Hypermobility of small joints (shown in distal phalange of index finger). Digital subtraction angiography images of bilateral common carotid arteries showing dissection of left internal carotid artery (E,F). Right internal carotid artery was normal. Axial (G) and coronal (H) maximum intensity projection (MIP) CT images showing aneurysmal dilatation of left hepatic artery. Coronal MIP images (I,J) of contrast enhanced CT show dissection involving left renal artery with multiple infarcts of renal parenchyma. Axial (K) and coronal (L) MIP CT images show dissection involving right renal artery and right common iliac artery.

FIGURE 2

Primary culture of skin derived fibroblasts from (A) age matched control (B) suspected vEDS patient. Immunofluorescence analysis of fibroblasts show (C) presence of Col3A1(Red) control fibroblasts whereas (D) patient fibroblasts show absence of Col3A1. Transmission electron microscopy of (E) control fibroblasts with normal morphology, (F) vEDS fibroblasts with altered morphology, arrows show intracytoplasmic lamellar vacuolar bodies. (G) Sequences of wild-type (1340-G) and mutant (1340-A) COL3A1 cDNA derived from patient skin fibroblasts. As vEDS patient is heterozygous for COL3A1 c.1340G > A mutation, sequencing of the region harboring the mutation results in detection of both guanine and adenine at position 1340. The G > A mutation leads to an exchange from glycine to aspartic acid at the protein level.