Measurement of serum tenascin-X in patients with congenital adrenal hyperplasia at risk for Ehlers–Danlos contiguous gene deletion syndrome CAH-X

Objective Approximately 10% of patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency carry a mutation that disrupts CYP21A2 and the flanking TNXB gene resulting in CAH-X, a contiguous gene deletion syndrome. TNXB encodes tenascin-X (TNX), an extracellular matrix glycoprotein that plays an important role in collagen organization. TNXB impairment is associated with Ehlers–Danlos syndrome. Symptoms include joint hypermobility, hernias and cardiac defects. We measured serum TNX using an antibody targeting the amino-terminal of the TNX protein in 161 subjects, including extensively genotyped and phenotyped CAH patients, their relatives, and healthy controls.