A 15-year-old girl complains of the absence of menstruations. Objectively, she has a short stature, a short neck with vertical skin folds on both sides, deformed auricles, and a low line of hair growth on her neck. Her chest is barrel-shaped, her elbow joints are deformed. There are multiple pigment spots on the skin of her torso and limbs. Her mammary glands are absent and the nipples are underdeveloped. Her intelligence is not impaired. There are no Barr bodies in the cells of her buccal epithelium. What is the most likely diagnosis in this case?