Biallelic mutations in Tenascin-X cause classical-like Ehlers-Danlos syndrome with slowly progressive muscular weakness

Tenascin-X, is an extracellular matrix glycoprotein expressed in skin, muscle, tendons, and blood vessels with an anti-adhesive function. Biallelic Tenascin-X mutations cause classical-like Ehlers-Danlos syndrome. We report a 46-year-old woman with slowly progressive weakness of the lower limbs and myalgia from age 28 years. In the past she had Raynaud's phenomenon, multiple sprains and joint dislocations, conjunctival haemorrhages and a colonic perforation during colonoscopy. Neurologic examination showed moderate asymmetric proximal and axial muscular weakness, distal amyotrophy of 4 limbs, moderate skin hyperextensibility, and hypermobility of distal joints of fingers. Whole body Magnetic Resonance Imaging showed symmetric fatty infiltration of thigh and leg muscles, with predominant atrophy of thighs. Next Generation Sequencing revealed two pathogenic TNXB variants, g.32024681C>G, c.7826-1G>C, and g.32016181dup, c.9998dupA, p.(Asn3333Lysfs*35). Western Blot and immunofluorescence studies confirmed a marked Tenascin-X reduction in both patient's serum and muscle. Here we further detail the clinical and genetic spectrum of a patient with classical-like Ehlers-Danlos syndrome and prominent muscle involvement.

Keywords: Myopathy; TNXB gene; Tenascin X; Whole body MRI.