Expanding the clinical and mutational spectrum of B4GALT7-spondylodysplastic Ehlers-Danlos syndrome

BACKGROUND: Spondylodysplastic EDS (spEDS) is a rare connective tissue disorder that groups the phenotypes caused by biallelic B4GALT7, B3GALT6, and SLC39A13 mutations. In the 2017 EDS nosology, minimal criteria (general and gene-specific) for a clinical suspicion of spEDS have been proposed, but molecular analysis is required to reach a definite diagnosis. The majority of spEDS patients presented with short stature, skin hyperextensibility, facial dysmorphisms, peculiar radiological findings, muscle hypotonia and joint laxity and/or its complications. To date only 7 patients with β4GALT7-deficiency (spEDS-B4GALT7) have been described and their clinical data suggested that, in addition to short stature and muscle hypotonia, radioulnar synostosis, hypermetropia, and delayed cognitive development might be a hallmark of this specific type of spEDS. Additional 22 patients affected with an overlapping phenotype, i.e., Larsen of Reunion Island syndrome, all carrying a homozygous B4GALT7 mutation, are also recognized. RESULTS: Herein, we report on a 30-year-old Moroccan woman who fitted the minimal criteria to suspect spEDS, but lacked radioulnar synostosis and intellectual disability and presented with neurosensorial hearing loss and limb edema of lymphatic origin. Sanger sequencing of B4GALT7 was performed since the evaluation of the spEDS gene-specific minor criteria suggested this specific subtype. Mutational screening revealed the homozygous c.829G>T, p.Glu277* pathogenetic variant leading to aberrant splicing. CONCLUSIONS: Our findings expand both the clinical and mutational spectrum of this ultrarare connective tissue disorder. The comparison of the patient’s features with those of the other spEDS and Larsen of Reunion Island syndrome patients reported up to now offers future perspectives for spEDS nosology and clinical research in this field.