The primary joint hypermobility syndrome (pJH) is an overlap disorder of connective-tissue dysplasias, which incorporates features seen in the Marfan syndromes (MFS), Ehlers-Danlos syndromes (EDS), and osteogenesis imperfecta. Patients with pJH usually present arthralgia, back pain, soft-tissue lesions, recurrent joint dislocation, or subluxation. Extraarticular features may include, e. g., striae cutis, keratoconus, easy bruising, mitral valve prolapse, aortic incompetence, aneurysms, pneumothorax, hernia, urinary incontinence, and pelvic floor prolapse. Due to the high frequency of critical dissection and rupture, the early recognition of rare life-threatening complications such as dilatation of the aortic root and aneurysms is important. Therefore, patients (and their family members) with pJH should also be examined for life-threatening features seen in MFS and EDS.