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