Ehlers-Danlos syndrome (EDS), classic type is a connective tissue disorder characterized by skin hyperextensibility, abnormal wound healing, and joint hypermobility. It includes two previously designated subtypes (EDS type I and EDS type II) that are now recognized to form a continuum of clinical findings. The skin is smooth, velvety to the touch, and hyperelastic; i.e., it extends easily and snaps back after release (unlike lax, redundant skin, as in cutis laxa). The skin is fragile, as manifested by splitting of the dermis following relatively minor trauma, especially over pressure points (knees, elbows) and areas prone to trauma (shins, forehead, chin). Wound healing is delayed, and stretching of scars after apparently successful primary wound healing is characteristic. Complications of joint hypermobility, such as dislocations of the shoulder, patella, digits, hip, radius, and clavicle, usually resolve spontaneously or are easily managed by the affected individual. Other features include hypotonia with delayed motor development, fatigue and muscle cramps, and easy bruising. Less common findings include mitral and tricuspid valve prolapse, aortic root dilatation, and spontaneous rupture of large arteries.
The diagnosis of EDS, classic type is established by family history and clinical examination. Quantitative and qualitative studies of type V collagen chains are usually not useful in confirming a diagnosis. At least 50% of individuals with classic EDS have an identifiable mutation in COL5A1 or COL5A2, the genes encoding type V collagen; however, this number may be an underestimate, since no prospective molecular studies of COL5A1 and COL5A2 have been performed in a clinically well-defined group. Molecular genetic testing for these two genes is available on a clinical basis.
EDS, classic type is inherited in an autosomal dominant manner. It is estimated that approximately 50% of affected individuals have inherited the disease-causing mutation from an affected parent, and approximately 50% of affected individuals have a de novo disease-causing mutation. Each child of an affected individual has a 50% chance of inheriting the mutation. Prenatal testing for pregnancies at increased risk may be possible for families in which the disease-causing mutation has been identified in an affected family member.