EDS caused by B4GALT7 deficiency (spEDS-B4GALT7) and B3GALT6 deficiency (spEDS-B3GALT6)
Characteristic clinical symptoms of spondylodysplastic Ehlers-Danlos syndromes (spEDS), previously referred to as progeroid subtypes, include an aged appearance, developmental delay, short stature, craniofacial dysproportion, generalized osteopenia, impaired wound healing, hypermobile joints, muscle hypotonia, and loose but elastic skin.
Molecular causes are homozygous or combined heterozygous variants in the B4GALT7 and B3GALT6 genes. Both genes encode a UDP-galactose: O-beta-D-xylosylprotein 4-beta-D-galactosyltransferase and beta-1,3-galactosyltransferase 6, respectively. Galactosyltransferase I deficiency results in deficiency of small proteodermatan sulfates within glycosaminoglycan biosynthesis. B3GALT6 variants were originally identified in spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL1).
EDS caused by SLC39A13 variants (spEDS-SLC39A13)
Patients with the very rare EDS type formerly known as spondylocheirodysplastic EDS (SCD-EDS) have thin, translucent, hyperextensible, velvety, fragile skin with atrophic scars; slender, tapered fingers; and joint contractures. Additional characteristic clinical symptoms include skeletal dysplasia (spondylo) with moderate short stature, and characteristic hand abnormalities with wrinkled palms and atrophy of the muscles at the base of the thumb and palm of the hand (cheiro).
spEDS-SLC39A13 is caused by variants in the zinc transporter gene SLC39A13. To date, only three homozygous loss-of-function variants in the SLC39A13 gene have been described in nine patients from three families. Patients with spEDS-SLC39A13 have a urinary LP/HP ratio of approximately 1.0, which is a value between controls and patients with kyphoscoliotic EDS (kEDS-PLOD1).
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