HIGH YIELD 2: Marfan's vs Homocystinuria vs Ehlers-Danlos

HIGH YIELD 2: Marfan's vs Homocystinuria vs Ehlers-Danlos High yield review for the USMLE Step 1 exam. Marfan's syndrome, Ehlers-danlos, and homocystinuria are three distinct diseases that affect connective tissue. They share similarities like tall stature, long fingers, scoliosis, high arched palate, chest wall deformities, joint hypermobility, and lens dislocation. Marfan's syndrome is caused by FBN1 gene mutation on chromosome 15, and it results in defective fibrillin-1. It causes aortic root dilation, and upward lens dislocation. Homocystinuria is caused by a defect in homocysteine breakdown, and it results in elevated levels of homocysteine, which is toxic to the body. It causes thrombosis and downward lens dislocation. Ehlers-Danlos syndrome is caused by a deficiency in type III collagen, and it results in hyperextensible skin, easy bruising and bleeding. It can cause vascular rupture, and it usually occurs in the arterial system. Patients with Marfan's syndrome present with scoliosis, long fingers and toes, and caved-in chest wall. Patients with homocystinuria present with developmental delay, long fingers and toes, and upward lens dislocation. Patients with Ehlers-Danlos syndrome present with recurrent bruising, soft hyperextensible skin, and joint hyperextensibility